had a chat with clive the other day about running high revs with my drag engine and decided to try to get the whole e shaft, rotors and counterweights balanced whilst everythings assembled on the shaft with flywheel on aswell.
Ive already lightened my rotors similar to the way racing beat mill the sides out on theres, but not realizing that this would throw everything out of balance!
thanks clive for kindly informing me on this by the way.
:Thumbs-up
what I cant get my head round is how you can balance a shaft with 2 rotors on, which are ofset to each other when the rotors can spin in any position rotationaly on the shaft.
Ive milled the sides of the rotors like the pic below but ive not gone as close to the side seal groove and outer oil ring groove, ive also found out how much weight racing beat take out of the counterweights for there lightened rotors, which I havent done yet see pics below.
Ive had a word with a guy in manchester who dynamicly balances crankshafts, he said he would have a go with everything assembled and take the weight of the counterweights to balance the full assembly, the guys never seen an e shaft or rotors before by the way!
my question is how do u stop the rotors spinning of the journals when balancing everything assembled??
Here is a pic of a Assembly being Ballanced. (this is manderville\'s ballancing set up)
Great idea to have it all balanced. There is no way we could run such high revs without the whole assembly being balanced. Took a lot of time to set-up, but worth it in the end.
every thing balance by bobweight (not rotors itself) etc.. but It\'s cost £300 to balanced,it worth every penny!!
PS ,
have you done snap rings in the rotors gear ring( lock up the gears to stop its walk out at high rev)
RPM\'s are all about loosing as Much wight from the Assembly as Poss but as the guy who Did my Ballancing said there int alot of Point in going too mad becouse once the Rotor is Full of oil how do you Account for that in the Prosses?
With mine Oviously having an Extra Rotor and Custom Shaft i have the the Advantage of having a Bearing in each Plate but i belive on 13b\'s you can get to a level where the Cetrifugal force of the Rotor its self can bend the E-shaft and Cause Contact with the Rotor Housing (hence high RPM need the weight reduction, But don\'t forget removing lots of weight will also Reduce the strenth)
Quote from: ian duncanPS ,
have you done snap rings in the rotors gear ring( lock up the gears to stop its walk out at high rev)
Snap rings are realy handy on NA aplications (long periods of high RPM) i don\'t know why but not many people use them on Turbo\'s? May be becouse of The Turbo producing most of its Power lower down??????
Theres a few companys in Japan that can supply balanced shafts etc.. for use in high rev applications, I think Revolution racing do them. You can also order a whole block too, although that\'d be a small fortune!
I have to admit even though i\'ve had mine done by a Big name engine Builder i\'m intrested how they get round the Oil problem?
hows it going grizly?
that pic looks like the rotors have side plates bolted on each face with allen bolts and big washers if u look closely, this is what I need to know how to keep the rotors from spinning of the journals when balancing but if u think about it the plate clamp setup that holds them on must be fully balanced to, then when u take the clamps or jig of how do u know its still balanced!
do you have a pic of a setup not spinning griz?
Quote from: Initial-DTheres a few companys in Japan that can supply balanced shafts etc.. for use in high rev applications, I think Revolution racing do them. You can also order a whole block too, although that\'d be a small fortune!
you can buy a fully balanced shaft, then when u put lightened rotors and counterweights on it your in the same boat,
each rotor is almost a 1lb lighter than stock so in theory you have to take the same amount of the heaviest part of the counterweights.
Quote from: stuart wizyhows it going grizly?
that pic looks like the rotors have side plates bolted on each face with allen bolts and big washers if u look closely, this is what I need to know how to keep the rotors from spinning of the journals when balancing but if u think about it the plate clamp setup that holds them on must be fully balanced to, then when u take the clamps or jig of how do u know its still balanced!
do you have a pic of a setup not spinning griz?
I\'m good..
I do have a Pic of an assembly being rigged up some where (Its a 35mm Pic so i\'ll have to dig it out and Scan it)
You are quite correct, when i spoke to the Guy who did mine he told me that the balancing is a black art and it will never be 100% spot on, even he said he has been doing it years and even know hes not sure he\'s doing it right (i hope he was Joking but thats what he said)
There is Lots of factors to take into account, Whats keeping the Rotor in the correct Place?? (i don\'t see Staitionary gears??) Whay about Oil in the Rotor (this alone will add weight and throw the Ballance out)
Quote from: stuart wizythat pic looks like the rotors have side plates bolted on each face with allen bolts and big washers if u look closely
Do you mean on the Pic i put up? Or the Racing beat one??
Quote from: ian duncanPS ,
have you done snap rings in the rotors gear ring( lock up the gears to stop its walk out at high rev)
no ive not done this , just lighten and balance and get the thing running first, I could do though, but u can go on forever and ever.
It looks like a 2mm recess in od of gear and in bore of rotor to let it snap in.
The recess in the od of the gear would have to be quite deep like a piston ring groove to allow it to compress in so you can push it in the bore, then it snaps in the recess in the bore of the rotor, wouldnt like to try and get it out though!!!
Quote from: GrizzlyDo you mean on the Pic i put up? Or the Racing beat one??
the pic u put up looks like the rotors have got allen bolts and big washers on the sides to hold them in position somehow
I don\'t belive it, I\'ve just been looking at mine, They are all well covered in grease but on one there is faint outlines of what look like dowls?? but they have been Machined down. I\'ve never noticed this before??
I\'ll have to take one to work and weigh it too see exactly how much they have been Played with? I\'ll have a Go at getting a Picture of it too but its not very Clear.
Do you think this could have been the Fixing for the ballance or do you think there could be Internal Work? (they don\'t look like Bolts)
Quote from: ian duncanPS ,
have you done snap rings in the rotors gear ring( lock up the gears to stop its walk out at high rev)
Has anyone actually seen the gears \'walk out\'at high rpm? appears to be a myth which doesn\'t apply to modern rotors.Mine have never moved,I have logged 12,600 rpm and probably been higher.
Quote from: TimrxmotorsHas anyone actually seen the gears \'walk out\'at high rpm? appears to be a myth which doesn\'t apply to modern rotors.Mine have never moved,I have logged 12,600 rpm and probably been higher.
To walk out, every thread on all the grub screws would need to be ripped out,
have u balanced your e shaft with everything on tim?
12,600rpm is seriously quick, I knew u where reving high by the sound of your motor at elvington but i didnt think to nearly 13 k!
I can balance the assembly myself between centres the oldschool way by just turning the whole thing in different positions and letting go, if it drops and stops, mark the bottom with a pen and add weight to the opposite side until it wont rotate in any position on its own. this is how we balance grinding wheels on all the large grinding machines that spin really quick.
This guy in manchester can do it on a dyamic balancing machine the same way they balance turbo shafts, its got an encoder on the end linked up to the shaft so it knows what angular position its at all the time and knows how many grams are being thrown out at that excact angle, thus remove weight at that angle, but how the hell u keep the rotors on when it spins up to high revs I dont know.
could you not machine some sleaves that are in 4 peices and balanced on a mandrel prior to fitting? this could be used to shim the rotors into position so when your doing the full balance the rotors don\'t move. would need it be tight to the eshaft as well but it should cancel itself out of the overall balance.
Shaun
Quote from: GrizzlyHere is a pic of a Assembly being Ballanced. (this is manderville\'s ballancing set up)
ive sussed it out,
im gona turn 2 spacers the same outside diamater as the 3 tip points of the rotors, the inside (bore) diamater bigger than bore of rotor bearing, drill amd tap the spacers in 3 places at the centres of the corner seal bores on your rotors.
now this spacer will fit on 1 face of the rotor with long allen bolts turned down in the middle to 2.8mm dia so they fit through the 3mm wide tip grooves but leaving the thread on the end to screw into the spacers with large washers on the oposite side.
measure the weight of the rotor empty then fill with oil and measure weight,
weigh the 3 allen screws and washers, turn down one side of the spacer until it weighs the same as your oil weight and clamp up and balance.
that would let you balance everything perfect with the rotors full of oil without guessing because the spacers are on the centre line of the rotors lined up with 3 tip points. (same rotating axis as the oil would be)
How would you go about the Timing of the Rotor spining on the E-shaft? or would that not realy matter as long as the Rotors weigh the wame?
thats what them allen bolts are holding on the rotors on your pic griz, its the only way to get the oil weight, the rotors will be free to spin in what angular position they want when rotated quick, they find there own balance if you think about it.
very dificult to rig up so they spin timing wise on the gears though without assebling stationary gears fixed somehow, theyve not done it on that pic anyway!
By the way have u seen how much racing beat charge for lightening the rotors and counterweights assembled by the way?!!!!!!!!!!:Thumbsup!
Yep... BIG BUCKS!!!!!!!!!!!!!
Not as bad as some of the other Performance shops in the US i\'m sure they send out the RB and wack there bit on.
For some odd reason AUS/NZ seems to be the best value for money, Prices seem quite good (just Shippings Bad)
For tight tolerance rotor configs, you can get a 2 piece E-shaft. benefits: it will already be balanced (although do balance the complete rotating assembly!) and it will be stronger(allowing for tighter tolerances).
a point to hold consideration for is torque resulting from rotating mass, without weight, you will have affected torque figures. Obviously, the revs are the key result of this process, which in an N/A applications is very usefull, but a charged drag application could benefit from greater low end torque.
I am glad people are now looking into/doing this though. Progress for the UK community
Quote from: ShyneFor tight tolerance rotor configs, you can get a 2 piece E-shaft. benefits: it will already be balanced (although do balance the complete rotating assembly!) and it will be stronger(allowing for tighter tolerances).
yep you got it, If you buy a 2pc crank they are usaly Ballanced for use with stock Rotors etc and i know my 3pc E-shaft came with Counterweights and the Rotors where done by Some one else and sent there for the whole lot of be ballanced. But thing is the Roller bearings have a reputation of Failing on High RPM/HP motors (some thing to do with Metal to metal wear as opossed to Plain bearings that sit of a Film of Oil)
If you think about it the engines are mass produced so they won\'t be Ballanced as an assembly rather matched and roughly Ballanced by weight. Acording to people that have not removed weight and just ballanced the Motor (13b\'s) they say the car feels smoother but for the effort involved its not that bigger deal.
The more i look into it the more i think there is a point in a Rotay where there is a Ballance between power and RPM if you have Big Power you can\'t run big RPm but if you have Lower Power high RPM can be achived.
totaly agree with the 2 piece central bearing shaft, no deflection , fully suported, no chatter or vibration at high rpm.
Ive looked at the ausy one from guru with the central bearing,a bit expensive me thinks at this stage,
im gona balance mine with the lighter rotors, use 3mm atkins and get racing.
regarding torque and power with different weighted rotating assemblys, dont forget mine is fully bridge ported so the power curve is at high rpm and climbs like a cliff face above 6,000rpm or so ive been told ,so it needs to rev as freely as possible with least amount of vibration in my opinion.
If i wanted big torque Id go yank.
My 12A has never been balanced,12A rotors with a 13B rear counterweight.You will know as soon as you start the engine if it is far out.I did find a company called \'Vibration Free\' who would have no problem balancing a rotor assembly.
knowing about rotors balancing but cannot put my word into writing,it\'s better to hear from the horse\'s mouth live than reading in this forum.
Its won\'t walk out at 1/4 mile down the strip but long race e.g 6hrs,12hrs etccc.., its will walk and jam the housing etc...
This country is UK, don\'t race the rotary car until fast and the furious film came out. so little knowlege what we got about seize-up!
In the pic, no rotors in the balancing machine, only bobweights,e shaft and counter weight!!
Tim, rev your engine to 11,000rpm until it\'s seize-up,using your timing watch and I bet it\'s 1hrs,39 sec!:Thumbs-up
And mine 13Bbp with rear 12A counter weight
Quote from: ian duncanknowing about rotors balancing but cannot put my word into writing,it\'s better to hear from the horse\'s mouth live than reading in this forum.
Its won\'t walk out at 1/4 mile down the strip but long race e.g 6hrs,12hrs etccc.., its will walk and jam the housing etc...
This country is UK, don\'t race the rotary car until fast and the furious film came out. so little knowlege what we got about seize-up!
In the pic, no rotors in the balancing machine, only bobweights,e shaft and counter weight!!
Tim, rev your engine to 11,000rpm until it\'s seize-up,using your timing watch and I bet it\'s 1hrs,39 sec!:Thumbs-up
And mine 13Bbp with rear 12A counter weight
ian there 3 very large bob weights on the e shaft dont u think!!:Giggle
do u know how to balance a fully assembled e shaft then??
Yes, its for 20B
bobweights must be the same as the weight of the rotor e.g rotor with all seals, bearing and weight of the oil etcccc.
13B rotor\'s Bob/weight\'s weight =4920grams
12A = 4260 grams
20B =3750 grams
The max rev of the balance is 720
drill out at counter weights only to balance it( see counter weight pic)
understand it okay!
got all info from Mazdaspeeddeveloment webset.:Thumbsup!
Quote from: ian duncanYes, its for 20B
bobweights must be the same as the weight of the rotor e.g rotor with all seals, bearing and weight of the oil etcccc.
13B rotor\'s Bob/weight\'s weight =4920grams
12A = 4260 grams
20B =3750 grams
The max rev of the balance is 720
drill out at counter weights only to balance it( see counter weight pic)
understand it okay!
got all info from Mazdaspeeddeveloment webset.:Thumbsup!
this is
just the same as screwing the side plates up on the rotors to add up the weight of the oil.
It will be easier for me just to turn up the spacers the same weight as the oil, tips, corner seals etc,clamp on 1 side of the rotors on the same centre line, then you can use the original egg shaped rotor instead of round turned weights which would have to be bored to the bearing size of the rotor.
easier to turn 2 spacers and keep turning weight of one side of each spacer till u get your desired weight.
For setting a jig up for balancing sh@t loads of assembled e shafts then the bob weights are the way to go, once youve got them made at each weight just re use time and time again, but i reckon using the original lightened rotors with weighted spacers clamped on the sides is more acurate.
cheers for that ian, i didnt actually think of turning the weights instead of using the rotors! im gona check that website out now.
http://www.nopistons.com/forums/index.php?showtopic=65446
Ah! the Formula!!!!, if its help to keep the brain going!!::2eek xconfused :3Confused :3Confused
(http://i121.photobucket.com/albums/o229/scot62/RotaryEngine92.jpg)
(http://i121.photobucket.com/albums/o229/scot62/RotaryEngine93.jpg)
any scientists on here then??:confused:
thats just totaly mashed my head up!!!!!!!!!!!
Hi
I have done this for many years now and i got all the information how to do it from a Mazdaspeed engine technician that i ran into at Mazda Rally Team in Belgium ( 1986 ).
The only right way to do this is that you calculate the weight on rotors all seals and springs and a small amount of oil and then you use a bobweight that you put on the shaft that is simulate the real weight in a running engine.
I have my own dynamic balance machine and have done this for many years on street and race engines here in Sweden.
A bad example is when you put a A/T rear counter weight on a M/T engine without rebalance the entire assembly and offen get fast worn out stationary bearings.
About the weight on rotors you need to use a lighter rotor if you going for high rev. If not the pressure on the stationary gear is to heavy and the gear will crack. A standard fd rotor should not rev more than 9000 rpm for short time but with a light weight race fd rotor you can rev 9,500 rpm constant.
/Jörgen Blennow
Rotary Performance Inc
Sweden
(sorry for my bad english )
Cheers Jörgen!
Jörgen, nice to see you posting on here.
Hope you\'ve had a great Christmas, and a happy new year to you and your family.
Fish
The balancing does not have to be done at any major revs as the out of balance distance of movement or oscillation is the same at any speed.
Also there are easier ways of doing it than using the bob weights.
It can be done as an entire rotating assembly with rotors at the same time.
It is important though to balance the rotors after lightening them on their own,once that is done it does not matter how the are on the E shaft as their own individual rotation does not affect the balancing of the whole assembly.
You need to allow a few ounces for oil in the rotors,but the high compression need a little more than the lower compression rotors.
Regards
Carl
Quote from: FishJörgen, nice to see you posting on here.
Hope you\'ve had a great Christmas, and a happy new year to you and your family.
Fish
Hi Dan :WaveBye
Wish you the same...
It\'s always nice with all the christmas food and the christmas gift :Santa .
/Jörgen
Quote from: CarlThe balancing does not have to be done at any major revs as the out of balance distance of movement or oscillation is the same at any speed.
Also there are easier ways of doing it than using the bob weights.
It can be done as an entire rotating assembly with rotors at the same time.
It is important though to balance the rotors after lightening them on their own,once that is done it does not matter how the are on the E shaft as their own individual rotation does not affect the balancing of the whole assembly.
You need to allow a few ounces for oil in the rotors,but the high compression need a little more than the lower compression rotors.
Regards
Carl
I dont agree with you ...
When spinning the assembly the unbalance is shown more if you spinn it faster but the unbalance is shown at the same degree at all the rpm.
If i balance at 720 rpm i get a value of the unbalance but if i spinn it up to 900 rpm i sometimes get a higher value becuse the vibaration increased the unbalance.
I dont say you can\'t use rotors as bob weight but i say it\'s a more difficult way to do it.
You need to add more weight on the rotor that compensate oil and some other stuff and you need to lock the rotor on the shaft so it not twist or turn when you spinn it. Another thing is that the rotor must be on right weight position (offset) on the shaft to get a successful balance.
If you use a bob weight you know where the center on the bobweight is and you can add or take of some weight from the bob weight so the weight is the right for the purpose.
The weight on the rotors affect the whole assembly so when you rebalance the assembly you actually match the wheight between rotor shaft and both counter weights.
If you have unbalance in one or all rotors then you affect the whole assembly becuse it spreads to other parts that is working together.
The oil weight in low or high compression rotors is slightly different and the casting in this rotors is also slightly different so the calculate oil weight is the same for both typ of rotors.
/Jörgen
Quote from: WankeltrimI dont agree with you ...
When spinning the assembly the unbalance is shown more if you spinn it faster but the unbalance is shown at the same degree at all the rpm.
If i balance at 720 rpm i get a value of the unbalance but if i spinn it up to 900 rpm i sometimes get a higher value becuse the vibaration increased the unbalance.
I dont say you can\'t use rotors as bob weight but i say it\'s a more difficult way to do it.
You need to add more weight on the rotor that compensate oil and some other stuff and you need to lock the rotor on the shaft so it not twist or turn when you spinn it. Another thing is that the rotor must be on right weight position (offset) on the shaft to get a successful balance.
If you use a bob weight you know where the center on the bobweight is and you can add or take of some weight from the bob weight so the weight is the right for the purpose.
The weight on the rotors affect the whole assembly so when you rebalance the assembly you actually match the wheight between rotor shaft and both counter weights.
If you have unbalance in one or all rotors then you affect the whole assembly becuse it spreads to other parts that is working together.
The oil weight in low or high compression rotors is slightly different and the casting in this rotors is also slightly different so the calculate oil weight is the same for both typ of rotors.
/Jörgen
Hi Jorgen,
I agree in part with what you have said,but I think you may have misunderstood me.
There is no more difference between running the parts at say 500 rpm and running them at 5000rpm,the amount of imbalance is the same,so there is no need to run really high rpm,even 300 rpm is enough.
Of course the rotating mass must reach a certain amount of rpm for the imbalance to be noticed,for example if we take it to the extreme and say run the parts at 1 rpm then that is too slow obviously.
In the high compression rotors they can and do hold more oil than the lower compression rotors simply becuase there is more space inside the rotor to hold oil.
When you spin the engine at higher rpm such as 900rpm,you are not getting higher imbalance,but instead you might be getting a harmonic vibration which is a completely different thing and is a consequence of the original imbalance,not something additional.This is caused by the imbalanced parts setting up a resonace frequency that can actually increase certain vibrations,but it is defintely not more imbalanced.
It is important to balance each rotor on their own first before balancing the entire assembly by either adding or removing material from the counterweights only.
When balancing the entire assembly it is relatively easy to hold the rotors on the shaft in the correct position,and I know that they do need to be in the exact position that they run in.
Once the whole assembly is balanced then you do not get any "Extra" harmonic vibrations at any revs.
That has been my experience.
Regards
Carl
i agree with carl. If you spin up the same arrangement at a different speed does the torque required change? I dont think so. \'inbalance\' is not the right word to use. regardless of rotational speed (i notice everybody has been using RPM and not the more mathematically correct radians/sec :D ) the magnitude of inblanace is the same. However, certain frequencies (or in this case dynamic rotational oscilations) may set up nodal wave frequencies and vibrations. This then follows the same principles as standing waves in a speaker: fundamental frequencies usually are followed by secondary and third order freqnency large-amplitude vibrations.
just my 5 pennies!
:)
cheers jorgen for some good info mate
If i was to use bob weights then instead of using my lightened rotors to balance, what do i turn the bob weights out of??
If i use ali they will be to big to make the weight of the rotor and if i turn them out of steel they will be to heavy because they are being turned from billet ,ie -no cast oilways in centre of turned bob weight so in theory they would be a lot smaller in od than the rotors outer measurements, if they are turned to whatever od they are with a bore size the same as the rotor bearing with a drilled and tapped hole through od into bore to use a brass grub screw to lock the turned bob weights on the journals on the e shaft they would be perfectly balanced because they are round, the od of steel bob weights would be quite small i guess but once turned just over the desired weight, its just a case of facing 1 side of the bob weight down until the rotor weight is acheived and then lock on journal with the brass grub screw so the journal is not marked nd balance.
this is the only way i can think of doing it, but ive read somewhere that the bob weights are plastic filled with sand to make the desired weight.
what do u use for your bob weights mate and what do u reckon my oil weight is for 1990 fc turbo rotors?
once again thanks for all your info mate
cheers
stuart
Quote from: CarlHi Jorgen,
I agree in part with what you have said,but I think you may have misunderstood me.
There is no more difference between running the parts at say 500 rpm and running them at 5000rpm,the amount of imbalance is the same,so there is no need to run really high rpm,even 300 rpm is enough.
Of course the rotating mass must reach a certain amount of rpm for the imbalance to be noticed,for example if we take it to the extreme and say run the parts at 1 rpm then that is too slow obviously.
In the high compression rotors they can and do hold more oil than the lower compression rotors simply becuase there is more space inside the rotor to hold oil.
When you spin the engine at higher rpm such as 900rpm,you are not getting higher imbalance,but instead you might be getting a harmonic vibration which is a completely different thing and is a consequence of the original imbalance,not something additional.This is caused by the imbalanced parts setting up a resonace frequency that can actually increase certain vibrations,but it is defintely not more imbalanced.
It is important to balance each rotor on their own first before balancing the entire assembly by either adding or removing material from the counterweights only.
When balancing the entire assembly it is relatively easy to hold the rotors on the shaft in the correct position,and I know that they do need to be in the exact position that they run in.
Once the whole assembly is balanced then you do not get any "Extra" harmonic vibrations at any revs.
That has been my experience.
Regards
Carl
Quote from: dubber91i agree with carl. If you spin up the same arrangement at a different speed does the torque required change? I dont think so. \'inbalance\' is not the right word to use. regardless of rotational speed (i notice everybody has been using RPM and not the more mathematically correct radians/sec :D ) the magnitude of inblanace is the same. However, certain frequencies (or in this case dynamic rotational oscilations) may set up nodal wave frequencies and vibrations. This then follows the same principles as standing waves in a speaker: fundamental frequencies usually are followed by secondary and third order freqnency large-amplitude vibrations.
just my 5 pennies!
:)
the faster you rotate something that is imbalanced the more vibration, harmonic vibration will occur, theres no need for all this scinece talk mate!
Im an engineer and have turned thousands of different things that are not running true (out of balance slightly) and trust me, u turn the revs up to high say 1500rpm and the machine will bounce around the workshop, everything will shake around,run the same workpiece at 200 rpm and u could turn it no probs !
higher the revs the more acurate the reading I say
Stuart,
I know what you are thinking,but I think you still misunderstand what we are on about,
The forces are greater yes,but the distance of movement of the out of balance item or Oscillation is the same.
The faster you rotate it the more oscillations per minute or second is what you get that is all.Each oscillation has more force at higher rpm,but it is over a progressively shorter period of time,so the faster you go the object moves the same distance back and forth,but with greater force as the item speeds up.
The object just does not get more out of balance,it still has the same amount of imbalance.there is no real need to run things much more than around 300 rpm for balancing,as once you have balanced the item it is balanced no matter what rpm it runs.That does not mean that Jorgen is wrong to do so at a higher speed,it is just not totally necessary,just do what is needed to get the job done.
At the end of the day as long as you get your parts balanced it does not really matter I suppose.
Regards
Carl
Quote from: CarlStuart
I know what you are thinking,but I think you still misunderstand what we are on about,
The forces are greater yes,but the distance of movement of the out of balance item or Oscillation is the same.
The faster you rotate it the more oscillations per minute or second is what you get that is all.Each oscillation has more force at higher rpm,but it is over a progressively shorter period of time,so the faster you go the object moves the same distance back and forth,but with greater force as the item speeds up.
The object just does not get more out of balance,it still has the same amount of imbalance.there is no real need to run things much more than around 300 rpm for balancing,as once you have balanced the item it is balanced no matter what rpm it runs.That does not mean that Jorgen is wrong to do so at a higher speed,it is just not totally necessary,just do what is needed to get the job done.
At the end of the day as long as you get your parts balanced it does not really matter I suppose.
Regards
Carl
cheers carl, i understand what u mean about the oscilation but going of my own experience with rotating parts for many years I guess ive come to my own conclusion!!!
it seems that this subject has very different views and methods all over the world from me trying to find this info out,
all i need to know is the oil weight and i can turn these bob weights up and have a play!!!
cheers again for all the info guys:WaveBye
i dont agree with the faster the RPM the more accurate the reading. It depends upon the application. Accurate in this sense is operating the shaft and dynamically balancing it at the RPMs it will experience in an engine (i.e. 900-12000 RPM). If you balance something at, say 20K RPM you may miss severall of the fundamental frequency nodes, and you will experience it during normal operation. Given that fundamental frequencies are always the greatest in magnitude i would consider these the most important frequencies engineer out.
However, what i am talking about is vibration, and NOT balance.
Again just my engineering 5 pennies ;)
Quote from: dubber91i dont agree with the faster the RPM the more accurate the reading. It depends upon the application. Accurate in this sense is operating the shaft and dynamically balancing it at the RPMs it will experience in an engine (i.e. 900-12000 RPM). If you balance something at, say 20K RPM you may miss severall of the fundamental frequency nodes, and you will experience it during normal operation. Given that fundamental frequencies are always the greatest in magnitude i would consider these the most important frequencies engineer out.
However, what i am talking about is vibration, and NOT balance.
Again just my engineering 5 pennies ;)
ok mate, I guess u know at bit about frequency nodes etc etc but listen to a simple explanation on vibration that any turner or cylindrical grinder will tell u the same thing because we work with things that spin round all day everyday, if there is vibration we get chatter when cutting so need to eliminate this by turning the revs down.
eg:-
put a piece of bar in a chuck on a laithe that is running out slightly say 1mm run out (out of balance slightly)
place a 10 pence stood on its side on the tailstock of the machine
spin the chuck at 200 revs 10 p will stay put
turn up the revs to say 2000rpm and the 10 p will fall over because of the vibration.
which reading is more acurate here high revs or low revs?
with chuck empty you can spin 2000 rpm with 10 p still stood upright.
I use this method a lot when im turning shafts that have slots, keyways, milled squares on etc that are out of balance to eliminate chatter caused through VIBRATION.
we build rotor milling and grinding machines,we machine every single component for each machine in house, when we build the workheads up on the rotor grinding machines we check for vibration all the way up to top revs on each individual machine upon final inspection to rule out vibration which would cause chatter when grinding.
http://www.renold.com/Renold/web/site/Products/MachineTools/Holroyd-Edgetek/Ancillary.asp
ok mate, Im only trying to help.
some observations on what you just said. 1mm run out means an amplitude of 2mm if you treat the rotational moment as a wave. The reason your 10p does not fall over at lower rpm is because your no where near the fundamental frequency of the assembly. Say for arguements sake that 2000RPM is your fundamental freqency. then, 4000RPM you may experience the secondary frequency. In between you have the physical INBALANCE of the assembly also producing mild (and more importantly more noticeable)oscilatory motion of the entire assembly.
Thats why it vibrates more at higher speeds.
dynamic BALANCE should not be affected by the speed of the rotation. Vibration is another matter alltogether.
thats why you can do it the \'oldschool\' way you talked about much earlier works.
Steve
ok mate, Im only trying to help.
some observations on what you just said. 1mm run out means an amplitude of 2mm if you treat the rotational moment as a wave. The reason your 10p does not fall over at lower rpm is because your no where near the fundamental frequency of the assembly. Say for arguements sake that 2000RPM is your fundamental freqency. then, 4000RPM you may experience the secondary frequency. In between you have the physical INBALANCE of the assembly also producing mild (and more importantly more noticeable)oscilatory motion of the entire assembly.
Thats why it vibrates more at higher speeds.
dynamic BALANCE should not be affected by the speed of the rotation. Vibration is another matter alltogether.
thats why you can do it the \'oldschool\' way you talked about much earlier works.
Steve
Quote from: dubber91ok mate, Im only trying to help
some observations on what you just said. 1mm run out means an amplitude of 2mm if you treat the rotational moment as a wave. The reason your 10p does not fall over at lower rpm is because your no where near the fundamental frequency of the assembly. Say for arguements sake that 2000RPM is your fundamental freqency. then, 4000RPM you may experience the secondary frequency. In between you have the physical INBALANCE of the assembly also producing mild (and more importantly more noticeable)oscilatory motion of the entire assembly.
Thats why it vibrates more at higher speeds.
dynamic BALANCE should not be affected by the speed of the rotation. Vibration is another matter alltogether.
thats why you can do it the \'oldschool\' way you talked about much earlier works.
Steve
cheers steve
the aim of what i am trying to do is allow the full rotating assembly to rotate much quicker than stock for longer periods of time whilst lowering the vibration without using the centre bearing which costs a fortune!
With my lightened rotors and a really good balance using the bob weight method above, i reckon it should rev higher with less vibration hopefully reducing the chatter that would be caused with apex seals chattering on the rotor housings at really high revs.
I could do it the oldschool way and then maybe take it to manchester for the dynamic balance to improve it from my balance.
what im thinking of doing is sticking the whole thing on one of our good laithe beds gripped in a collet at one end, revolving centre at the other end and 2 roller steadys on the 2 main journals bearings so that the origanal suporting method is achieved, then spin up at different revs and get our inspector to take some readings on vibration up to top revs.
get before and after readings to see how much difference it as actually made.
Interesting little project that wont cost me anything but the dynamic balance.
I just need to know the oil weight, are the rotors full of oil or say half full cause of centrifugal force when spinning, thats what i really need to know?
Again cheers for any info by everyone
cheers
stu
So the big question is at what frequency does resonance occur in the assembly.
Shaun
or what frequencIES :)
you will never engineer them out. Vibration is much harder to deal with than balance: balance is simple static and dynamic equations whilst vibration and \'noise\' are more difficult. It is all down to wavelength, and the damping on the system. the damping in this case is the oil pressure on the journals, which is largely non-adjustatable. IIRC the lower the rotating masses, the higher the fundamental frequency, thus noise and vibration on a lightened assembly should be taken above the range on the stock motor, and should not cause you troubles.
At the end of the day dynamic balancing is a simple case of balancing the equations shown above. distances a and b are generally fixed, thus it is a case of adjusting the radius of rotation of the balancing masses, and the size of the masses themselves. The problem occurs because the shaft itself is not a simple element, rotors dont have fixed centres of mass, and the assembly is not supported by point supports. Thats why dynamic balancing is done practically rather than mathematically.
As with anything mechanical, you can only go so far with balancing: there are too many variables. The shaft may expand, the rotors change size, the oil changes viscosity and the bearing/shaft interface changes. Like using a timing light to time the engine, you can balance it just so, but it will not remain dynamically balance in all occurences. Your job is to ensure it is for the majority of driving scenarios and you dont end up with a motor that shakes itself to bits!
Good luck with it all: Im sure it will be worth it.
Steve
Quote from: dubber91or what frequencIES :)
you will never engineer them out. Vibration is much harder to deal with than balance: balance is simple static and dynamic equations whilst vibration and \'noise\' are more difficult. It is all down to wavelength, and the damping on the system. the damping in this case is the oil pressure on the journals, which is largely non-adjustatable. IIRC the lower the rotating masses, the higher the fundamental frequency, thus noise and vibration on a lightened assembly should be taken above the range on the stock motor, and should not cause you troubles.
At the end of the day dynamic balancing is a simple case of balancing the equations shown above. distances a and b are generally fixed, thus it is a case of adjusting the radius of rotation of the balancing masses, and the size of the masses themselves. The problem occurs because the shaft itself is not a simple element, rotors dont have fixed centres of mass, and the assembly is not supported by point supports. Thats why dynamic balancing is done practically rather than mathematically.
As with anything mechanical, you can only go so far with balancing: there are too many variables. The shaft may expand, the rotors change size, the oil changes viscosity and the bearing/shaft interface changes. Like using a timing light to time the engine, you can balance it just so, but it will not remain dynamically balance in all occurences. Your job is to ensure it is for the majority of driving scenarios and you dont end up with a motor that shakes itself to bits!
Good luck with it all: Im sure it will be worth it.
Steve
so in theory a less mass rotating of centre object ie rotors, should reduce vibration at higher speeds if it is balanced.
I would love to rev over 10,000rpm knowing she is lightened and balanced as well as u can possibly get.
Ive read some good write ups on apex seal chatter occuring on stock 13bs running over 9k, stating that the motor can loose compression because of the intermitant bounce of the seals on and of the rotor housings through the vibration leading to higher combustion temps, warped seals and even full det.
Idealy the centre bearing would cure a lot of the vibration at extreme revs.
The guys in puerto rico seem to know a bit about high reving rotorys,
listen to this of the line:-http://www.rotorespr.net/forum/viewtopic.php?t=1469
http://www.rotorespr.net/forum/viewtopic.php?t=1469
Quote from: stuart wizyso in theory a less mass rotating of centre object ie rotors, should reduce vibration at higher speeds if it is balanced.
I would love to rev over 10,000rpm knowing she is lightened and balanced as well as u can possibly get.
Ive read some good write ups on apex seal chatter occuring on stock 13bs running over 9k, stating that the motor can loose compression because of the intermitant bounce of the seals on and of the rotor housings through the vibration leading to higher combustion temps, warped seals and even full det.
Idealy the centre bearing would cure a lot of the vibration at extreme revs.
The guys in puerto rico seem to know a bit about high reving rotorys,
listen to this of the line:-http://www.rotorespr.net/forum/viewtopic.php?t=1469
not less vibration.....but the resonant frequency should increase. But it is impossible to say by how much. The issue is then that each component in the engine has a resonat frequency. Anything that acts as a mass and spring. That means that side, apex corner and oil control rings all have separate resonant frequencies! Obviously mazda didnt have much problem with resonance and noise, or did well to engineer it out in there original design.....
Quote from: dubber91not less vibration.....but the resonant frequency should increase. But it is impossible to say by how much. The issue is then that each component in the engine has a resonat frequency. Anything that acts as a mass and spring. That means that side, apex corner and oil control rings all have separate resonant frequencies! Obviously mazda didnt have much problem with resonance and noise, or did well to engineer it out in there original design.....
just found this through pineapple racing, my theory is right:Giggle
Technology For Low Vibration, Distinctive Rotary Sound
Dynamically Balanced Rotors: To further refine the superior balance of the twin-rotor configuration, Mazda shifted from the previous static balance setting and instead adopted dynamic balance calculated from the mass of oil entering the rotors. This improvement, together with the effect of the long span engine mount system (mentioned previously) realises extremely low vibration.
this is info Ive found on the renesis engine improved on 13b so it seems all rx8s are dynamicly balanced with oil weight worked out.
also this for the renesis:-
Lightweight Rotor, Three Injectors Per Rotor, And Long-Span Engine Mount: The previous 13B-REW engine generated its maximum power output at 6500 rpm, whereas the Renesis power peak comes in at 8200 rpm. This step-up to a higher revving engine was achieved by virtue of an 11 per cent reduction in rotor weight. Additionally, the flywheel weight has been reduced by some 20 per cent compared with the previous engine. Combined, these weight-saving measures reduce inertia to assure the quick response befitting a genuine sports car engine.
:) all adds up doesnt it?
As it happens the original 13bs are all \'dynamically balanced\' but not to the extent of the later REW motor. The dynamic balance of earlier engines is mathematical: the assemblies arent physically checked for balance. This obviously takes out massive amounts of time and therefoe cost to the OEMs. Each component would just be weighed to ensure relativly close tolerencing on a mathematically (and probably physically) balanced model.
New CNC and closer tolering of components mean dynamic balancing is possible.
Remember by reducing rotating mass (and affective inertia) you will lose engine braking performance. Not that its too much of an issue ;)
got it, just need to take difference between my lightened rotor and stock rotor from 5474gram , it doesnt say if this includes oilweight though:confused:
see below:-
http://www.mazdamotorsports.com/webapp/wcs/stores/servlet/Tech?storeId=10001&subject=balancing
theoretically. so long as the rotating radius of the counterweights and Centre of gravity of each rotor doesnt change
Quote from: TimrxmotorsMy 12A has never been balanced,12A rotors with a 13B rear counterweight.You will know as soon as you start the engine if it is far out.I did find a company called \'Vibration Free\' who would have no problem balancing a rotor assembly.
Latest is,my engine does need balancing,mainly because I have a \'D\' and a \'B\' weight rotors.I have come to the conclusion there are 2 ways to balance the rotating assembly.
The first way is to balance the shaft with counterweights and rotors.It appears Mazda do this with the RX8 engine,they inject a gel into the rotor to make up oil weight.There are no balance holes in the rotor,they are balanced by adjusting the counterweights.I don\'t know how they attach the rotors.Other people use a bob weight to replace the rotor.
The second way is the way I will have it done.To balance the shaft first,then balanced with counterweights.The rotors will be made exactly the same weight,then balanced individually.It appears Mazda balanced each RX7 rotor,but were not weight matched,just close,within 50g.
The result should be a far better balanced engine than I\'ve ever had!
I did speak to \'Vibration Free\',he balances the whole built up block,so I guess the rotors are dragged around with no proper lubrication.He has done Carl\'s 4 rotor and 3 rotor engines this way.Think I\'ll pass on that one,the bloke is not very helpful at all.
We have always balanced the eccentric shaft,rotors,flywheel and balance weights as a unit.The rotors were lightened to choice weight first to within 1 gram of each other.
Hi
The right way to do this is that you get two rotors with same weight and then you made bobweight that is matched to your rotor weight including oil and all seals and springs and put them on the shaft. If you have a light weight flywheel then you first balance the shaft with balance weight but without the flywheel and when this is done then you put the flywheel on and balance your flywheel ( after that you can put your clutch on and balance the clutch for it self ).
We have done this for more than 20 years and i got all information from a japanese that we meet at MazdaRallyeTeamEurope when Mazda compete with the first gen Rx7 in Gr-B. This japanese was a engine technician that work at Mazdaspeed in japan so i think he knew how to do.
(http://www.rotaryperformance.se/images/articles/trim5.jpg)
/Jörgen Blennow
Rotary Performance
Sweden
i can turn bob weights with the corect bore size and od as a rotor and face up 1 end to get the required weight but how do you stop the weights spining of the shaft when balancing? I thought of 1hole drilled and tapped from od throgh to bore so a grub screw could be used to hold the bob weight on the journal, is that how you do it?
cheers
stu
YES .....
But the bobweight dont have the rotor shape :)
what sort of revs have you run up to with your balaced assembly in a motor and did you use a centre bearing type e shaft?
cheers
stu
Quote from: WankeltrimHi
The right way to do this is that you get two rotors with same weight and then you made bobweight that is matched to your rotor weight including oil and all seals and springs and put them on the shaft. If you have a light weight flywheel then you first balance the shaft with balance weight but without the flywheel and when this is done then you put the flywheel on and balance your flywheel ( after that you can put your clutch on and balance the clutch for it self ).
We have done this for more than 20 years and i got all information from a japanese that we meet at MazdaRallyeTeamEurope when Mazda compete with the first gen Rx7 in Gr-B. This japanese was a engine technician that work at Mazdaspeed in japan so i think he knew how to do.
(http://www.rotaryperformance.se/images/articles/trim5.jpg)
/Jörgen Blennow
Rotary Performance
Sweden
If it is done with the bobweights,all balanced fine,then if the bobweights are removed would the remaining shaft and counterweights be in balance? Put another way,are the counterweights at all balancing the rotors,or do the rotors balance each other?
Quote from: stuart wizywhat sort of revs have you run up to with your balaced assembly in a motor and did you use a centre bearing type e shaft?
cheers
stu
The balance has nothing to do with the rev limit. It\'s the weight of your rotors that sets the limit.
Mazdas 13G rotor that was the lightest rotor that was produced has a weight of 3750g without bearing. With this rotors they had a rev limit that was 10.400rpm so with the production rotors the rev limit should be around 9-9.500rpm.
No i dont use 2 piece shafts becuse there are no reason to do that if the balance is done well.
Quote from: TimrxmotorsIf it is done with the bobweights,all balanced fine,then if the bobweights are removed would the remaining shaft and counterweights be in balance? Put another way,are the counterweights at all balancing the rotors,or do the rotors balance each other?
The counter weights are balancing the rotor weight.