full balancing of e shaft rotors and counterweights assembled

[stuart wizy]

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!

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.

[Grizzly]

http://www.nopistons.com/forums/index.php?showtopic=65446

[RotorHeid]

Ah! the  Formula!!!!, if its help to keep the brain going!!::2eek xconfused :3Confused :3Confused

[stuart wizy]

any scientists on here then??:confused:
thats just totaly mashed my head up!!!!!!!!!!!

[Wankeltrim]

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 )

[88GT-R]

Cheers Jörgen!

[Fish]

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

[Carl]

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

[Wankeltrim]

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

Hi Dan :WaveBye
Wish you the same...
It\'s always nice with all the christmas food and the christmas gift :Santa .

/Jörgen

[Wankeltrim]

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

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

[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

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

[dubber91]

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 ) 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!

[stuart wizy]

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

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

[stuart wizy]

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 ) 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

[Carl]

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