How do you balence driveshafts oldschool?

I keep getting customers in the shop wanting me to do driveshaft work. I know there is a way to balence a driveshaft without a computerized machine. I have been doing skidder driveshafts for a while, but there very short and dont turn very fast. I am wanting to do large tractor trucks. Any advise or pics?

Chris

FWIW I true them to run less than .010 TIR at each end and they always run smooth for me. The fastest I've ever turned one was 9600 rpm, trucks see less than 3000 so it should work fine there too. The driveshaft components are neutral balanced by themselves, if you keep them true and make an even weld, the finished product is theoretically in balance.

The local truck body installer does the same thing and has no trouble.

?????????
Can you elaborate on how you true them, what techniques ect.

They used to do it a makeshift way with hose clamps

Chris --

Back in the olden days we used to jack the drive wheels off the ground, put it in gear, and run the driveline speed up to something over the legal limit. We'd then take a piece of chalk and ease it gently toward the driveshaft just behind the shaft's front universal until the chalk contacted the shaft. Next, we did the same thing just in front of the shaft's rear universal.

As you'd expect, the chalk mark ends up on the heavy side of the shaft. We'd install a couple of worm drive hose clamps at each end of the drive shaft, positioning the worms 180 degrees from the chalk marks, and then repeat the chalk marking. Usually the new chalk marks would be on the opposite sides of the drive shaft, showing that the worms were too heavy.

So then we'd move the two clamps at each end of the shaft "equal and opposite" each other thirty degrees or so before re-remarking the shaft.

Balancing a drive shaft this way is "old school" for sure, but it didn't take much practice to develop the skill it took to reach an acceptable balance in a couple of tries.

(Not being all that wild about crawling underneath a jackstanded car or truck while the driveline is running at 75 miles an hour, I made an extension chalk holder from an old broom handle. A 3/8 inch hole drilled crosswise through the broom handle, a sawsplit, and a couple of small hose clamps to close the hole on the chalk made marking the driveshaft a reach-it-from-outside proposition.)

Even using the extension handle on the chalk, though, I doubt if that old technique would pass muster with the workplace safety folks today.

John

I wonder if the chalk method would work with chucking it up in the lathe and spinning it?

Chris

You keep the heavy side and the light side on the same side...

EASY

Years ago, I used to work for NEAPCO. All of the driveshafts that we built were dynamic balanced. I have heard of people building Ag shafts and static balancing them, but they only run at 1,000 rpm.

Here's a good site to explain http://www.maintenanceworld.com/Articles/grimmitchell/understandingthe.html

Our equipment came from Balance technology. You ahve to do a lot of shafts to pay for the equipment let alone your time. The shops around here that balance get $30 to do a driveshaft.
JR

To true them, I chuck the slip yoke in the lathe chuck, and support the other end of the driveshaft tube in a steadyrest. I indicate the unwelded end attached to the slip yoke within .010 by tapping with a soft mallet, then I tack weld, check again, and finish weld. In your case you would need a mating yoke to attach to the lathe to hold your U-joint because trucks don't use slip yokes like autos do. How are you doing the shafts you are doing now?

I did a few driveshaft rebuilds years ago and one recently as an emergency repair for a friend. These were light to medium truck dirveshafts, so no idea as to how fast they ran. What I did was to salvage the yokes by cutting thru the weld that held them to the driveshaft tubes. I cut the tubing off fairly close to the yoke and chucked it in the lathe. I indicated it as best i could, and supported the yoke on a tailstock center. Using a sharp toolbit, I was able to turn thru the weld and re-establish a square shoulder on the yoke.

The tubes had been pretty well "wound up" or bowed. Having the yokes cleaned up, I then fitted theminto new mechanical steel tubing. The yokes had a good boss or pilot to drive into the tubing, and had a square shoulder. I cut the tubing on a band cutoff saw and then cleaned it up with a facing cut using a steady rest.

I was lucky in that the yokes had centers in them. With the driveshaft supported on centers, I then put my ground right up close to where I was going to weld. I "quartered" the shaft and put on four tack welds, going 12:00, then rolling the shaft to 6:00, then rolling to 3:00 and then to 9;00. I was using 3/32" diameter E 7018 electrode and ran just the smallest tacks. I checked the shaft for true and things were probably within about 0.010-0.015" TIR. How much of this was due to bow in the tubing and how much was due to things cocking was something I didn't bother to find out. I had some cold drawn mechanical steel tubing (I believe it was "DOM" or drawn over mandrel) for making the new driveshafts. How straight it was as-received is also something I never checked.

After I had both yokes tacked on, I then welded my root pass. I did this also by breaking the root pass into segments and doing it in a sequence wiht a "backstep". I ran a cover pass in the same sort of sequence. This didn't take things any more out of true.

Not knowing what else to do and having no means to do a dynamic balance, I did a static balance with the shaft supported on the lathe centers. I spun the shaft by hand and marked where the heavy side was. I did a few such spins and got a consistent heavy side. I took some nuts and duct taped them to the light side as trial weights. When I got things to balance out to where the shaft would not stop in the same place twice, I called it balanced. I then weighed the nuts and cut some steel flatbar of a little more weight than the nuts. With some grinding, I had the flat bar weighing what the nuts had weighed. I tack-welded the flatbar to the driveshaft tube and verified the thing was still in static balance.

I have done this on a few shafts. I wonder about blancing out of plane, since the shaft will run at an angle and I was balancing with the shaft laying horizontal.

As I noted, these were fairly short shafts for light trucks. That was almost 30 years ago. One truck was an F-250 and the other was an old Cornbinder Scout.

The last driveshaft I repaired was for a 1946 Dodge dump truck. That was about two years ago. Nothing turning very fast. The old Dodge gets around at about 45 mph when my buddy runs it to haul firewood locally. I guess the shafts ran OK, as I never heard any complaints of vibration from the people who drove those trucks.

I also modifed a couple of AG PTO shafts. These had to be shortened. These used a square telescoping section rather than a spline. The fit of the square telescoping section was none too good. I shortened things up and rewelded. These shafts never looked to be blanaced, and I saw no real way to do a static balance. Running a 6 foot snow blower or a bush hog at speed on a tractor PTO with a pretty good angle on them, these shafts run with surprisingly little vibration.

I last time I had to balance a shaft was on a new '84 Dodge van. I used John Garner's method. It worked for all the years I had the vehicle. Mine was so bad I had to add a little sliver of alum off the shear under the band clamp to get it to quiet down.

TMD