driveshaft balancing

[Daniel M2]

Hi Pat,

 

I have a DS question for you, do you mind chatting by phone?

I'm in Florida 407-832-2222 or I can call you?

 

Kind regards,

[PatAllen]

22 minutes ago, Daniel M2 said:

Hi Pat,

 

I have a DS question for you, do you mind chatting by phone?

I'm in Florida 407-832-2222 or I can call you?

 

Kind regards,

can you PM me from this forum ?

a call from florida to quebec is not the best solution imho...

[TobyB]

2 hours ago, PatAllen said:

maybe if they where balanced down enough they wouldn kill the stuff at higher revs ?

fwiw it is not easy to find high speed motor to do high speed balancing, maybe with a belt reduction or something else.

Yeah, they said something similar- but then, at 3k, their balancing wasn't very precise, and I think that

was a big part of the problem...

 

I have a bigger DC motor that I've been hanging onto for this sort of project-  it makes it more complicated,

requiring a servo controller, but also allows a much larger speed range.  

 

t

[PatAllen]

if you want to do high speed balancing you need a 3phase induction motor,and ultimately a feedback encoder, the speed needs to be acurate and precise and repeatable, for the vibration analyser itself. also, depending on the method, the motor itself need to be isolated from the fixture (rubber mounts and whats not). i am using a powerflex40 drive with a 3phase special motor that generates extremely few vibrations, and i can still measure it beyond some limits at 1800rpm so i just cant imagine what it would be at 3000+ rpm...this is serious stuff.

[TobyB]

Agreed- as in, don't be in the same room as the driveshaft is!

 

t

[tzei]

I did a bit of a research and found that shops uses 700 or 1400 rpm for balancing. 

[halboyles]

Along the same line, I got tired of trying to eyeball-align the front of the driveshaft with the transmission so I created an alignment tool that bolts between the tranny and driveshaft to keep them perfectly parallel while you make adjustments to the engine/tranny mounts and get the CSB in the right position.  These are essentially the same as what Pat is using on his balancing machine.  This guarantees that there is minimum flex in the guibo and should make them live longer.  It could potentially help with some of the vibration in the driveshaft itself.  PM me if you are interested.

[PatAllen]

technically speaking, if the drive shaft is properly mounted on the balancer, and that there is no other induced vibrations, such as bad center bearing, holder bearing and motor, driving it "faster" just makes the inbalance apears larger. So in other words, running it at 2000rpm and balancing it as far as you can, if not, near zero, it should gives very good result even at 6000rpm. Welding a washer is not a professionnal balance method. What are the chances that the washer is exactly the right weight ?? this makes me laugh a lot.

 

Other Problem, most flanges and mounts on the car itself has tolerances that are way off, i have several differentials that i measured 0,010" inches of offset on the flage so the DS will be this much off, on a normal street car this isnt much problem but if the DS spins at 7000+rpm in autocross then it needs to be balanced on the car itself.

[PatAllen]

36 minutes ago, halboyles said:

Along the same line, I got tired of trying to eyeball-align the front of the driveshaft with the transmission so I created an alignment tool that bolts between the tranny and driveshaft to keep them perfectly parallel while you make adjustments to the engine/tranny mounts and get the CSB in the right position.  These are essentially the same as what Pat is using on his balancing machine.  This guarantees that there is minimum flex in the guibo and should make them live longer.  It could potentially help with some of the vibration in the driveshaft itself.  PM me if you are interested.

not exactly, my flages simulates various differentials mounts to adapt different driveshaft, not the guibo. on the guibo side i have only a 14mm shaft that i slide on the DS on to. it is driven on the other end (differential side)

[JohnS]

Love seeing the mad scientist at work.  Keep it up Pat!

[PaulTWinterton]

23 minutes ago, PatAllen said:

Welding a washer is not a professionnal balance method. What are the chances that the washer is exactly the right weight ?? this makes me laugh a lot.

 

Couldn't agree more.  I didn't watch my guy do the job, and I wonder what his process was.  I can't follow up because he is longer in business, like so many small automotive shops.  

 

Edit:  Just looked at my DS.  It's out of the car at the moment.  The washer that I thought he'd welded on was actually one of those DS balance weights that are referenced earlier in this thread.

 

Can your set up define the amount of weight needed and the location?  Just curious.  Makes me think of the commercial wheel balancing machines that spit out the data for each balance requirement.

 

Lastly, how do you deal with the circlip version UJ vs peened original.  Is there a channel to insert a circlip?

[PatAllen]

there are calculations that can be done, according to the reading of the machine (inches of movement or velocity), and the diameter of the shaft, to come up to the exact amount of ounces needed. there is also another method where you put a known weight and check where the new vibes is on and the amount and you plot a graph and boom it gives you the exact amount of imbalance.

 

otherwise i keep add weight in small increments up until i am "satisfied". from my experiments is it never a fixed amount like 5-10-15-20 ounces like a tire balancing machine....it need to be far more acurate than that but i guess balancers use what they have and if its within a given limit they call it "ok"....

 

other than machining a groove in the yoke, which is very hard and makes centering the joint very difficult, i prefer tacking it in place, once zeroed on the machine. some others put a large washer in front of the cup and tack the washer instead.

 

BOOM read this....very informative

 

https://www.balmacinc.com/downloads/BBookSingle.pdf

 

[PatAllen]

38 minutes ago, PaulTWinterton said:

 

Couldn't agree more.  I didn't watch my guy do the job, and I wonder what his process was.  I can't follow up because he is longer in business, like so many small automotive shops.  

 

Edit:  Just looked at my DS.  It's out of the car at the moment.  The washer that I thought he'd welded on was actually one of those DS balance weights that are referenced earlier in this thread.

 

Can your set up define the amount of weight needed and the location?  Just curious.  Makes me think of the commercial wheel balancing machines that spit out the data for each balance requirement.

 

Lastly, how do you deal with the circlip version UJ vs peened original.  Is there a channel to insert a circlip?

one thing i also discovered, and i was very mad of this, by simply welding on the shaft, the heat and thermal stress of the weld distort the metal and fuck up all the balance job. maybe a real spot weld that makes a very tiny weld is the cure but so far...welding on a shaft like a mad person is not a solution

[halboyles]

12 minutes ago, PatAllen said:

welding on a shaft like a mad person is not a solution

Is there another way to weld?

[PatAllen]

10 minutes ago, halboyles said:

Is there another way to weld?

i am a mad person so i dont know how to weld...

 

actualy using hose clamps is cheap, easy and indefinitely adjustable, it is just not sexy at all.

i tought also about using magnets and/or epoxy glue

 

i fix often high speed motors, and i see that manufacturers use a special epoxy as balancing media. like a puty and it freezes in there somehow...