swing arm spindle diameter

'71 Commando. Removed swing arm to check bearings and to see why fitting rear wheel so difficult. Swing arm was about .030" narrower at axle end than others in frame shop. No problem to widen a bit. Swing arm spindle measured .8750 everywhere except where fits into right side cradle: .8745". Received a new spindle - it measured .8742". Old Britts website says their replacements are .0845" ( also offer one .005" oversize). I would like to source one that is .875 like my original. Anybody measured a new one and can report what size was and source?
Doug

Spindle bushings and cradle plate holes are
. 878" now
How about getting a + .005" shaft and turning down or grinding to .877" ?

The cradle wallows out so likely on size in middle, so buy oversize spindle and ream all out to its OD.

0.8750 for all practical purposes is pretty darn close to 0.8745, which is what you measured as wear on one side of the spindle. It is only half a thousand difference. I think you may have mistyped, as Old Britts says their new spindles are 0.8745. Again, only half a thousand below nominal. I doubt it would make any practical difference, assuming the cradle and bushes are within specs. There is every chance that any spindle you buy will be plus or minus 0.0005, just based on manufacturing tolerances. And you could drive yourself nuts looking for that kind of tolerance off the shelf. I agree with Kommando: if you want a perfect fit, buy an oversize spindle and ream everything else. Even then, you would be asking the machine shop to ream with less than a 0.0005 tolerance, which will probably cause them to look at you kind of funny.

The manual says the spindle is an easy push fit in the frame. Thats a load of shiite. If it is easy to push into place it will flog out like they all did.

The spindle needs to be an interference fit for it to stay put and not work loose.

I agree with the precision fit idea. Could someone detail how to make a tool to hone the cradle?

You could possibly use an adjustable parallel reamer but it would probably chatter. Best is a fixed spiral reamer. Then make the spindle oversize to suit. A good engineer could tell you what the interference fit would be for that size. i have forgotten so wont advise.

You don't need an interference fit if you add Kegler mounts at the same time.

No need for reaming or oversize spindle with the Kegler clamp mod.


Corrected broken links on the doov.com page.

kerinorton said:

The manual says the spindle is an easy push fit in the frame. Thats a load of shiite. If it is easy to push into place it will flog out like they all did.

Click to expand...

Mine is a sliding fit, like the bushings in the gearbox. Swingarm is still tight after 45 years.

If you have a sloppy swingarm tube fit, but your spindle/bushing fit is good, then you just add the kegler clamps. No need to get an oversize spindle.

I don't see what an oversize spindle does to fix any swingarm problem. Either the cradle's swingarm tube gets wallowed out and sloppy, so you add the clamps to correct the flaw in the swingarm tube, OR you replace the spindle and bushings if there is a sloppy fit between the spindle and bushings.

All the oversize spindle does is force you to ream the bushings. You would be better off just buying a new stock spindle and new bushings to fix that kind of play. An oversize spindle doesn't fix the problem with the swingarm tube, but the kegler clamps does fix it... No excessive play between the swingarm tube and spindle, and no excessive play between the spindle and the bushings... and you'll be set.

My bike had horrible handling due to the wallowed out swingarm tube. As a young man, I tried changing the swingarm bushings and it didn't improved the handling. At the time I really didn't see the big picture and rode the bike like that for decades.... Then, I read about the kegler clamp modification here on the site, and I realized this was the cure to handling issue that I could not track down... My bike handles really well now.... thanks to the site and Mr. Kegler.

.

I was in the lucky position of being able to machine my swing arm pivot tube and bushes out to plus 5 thou
I hadn't heard of the Kegler back then
I also copied the MK3 cotter pin arrangement
I'd seen other conversions with nuts welded on the tube etc

Lets face it. In the early 70's, this forum wasn't invented. Mr keglar wasn't known. I am an auto engineer trained to work on lots if different vehicles and I was good at fixing the king pins on the early vehicles [ trucks included ]. If you had a sloppy fit in a king pin eye, you had to ream it out and fit an oversize king pin, which you were always best to fit with an interference fit. The swing arm on a commando is just like a kingpin.
I fixed mine in the early 70's and have had no trouble since. The tube between the g/box cradle is too thin to act like the eye on the solid axles of yesteryear. If they had put a decent tube in there in the first place and treated it like a real king pin, we would not have had these issues. It was a poor design and mr keglaqr came up with a good solution. That solution should have been designed into the bike in the first place. Maybe a design with tapered roller bearings.

This bike was built on a budget and churned out in the thousands. The general idea in those days was give them to the customer and hope they didn't complain. If they did, leave if to poor mechanics to solve the issues. They always got the blame in the end anyway.

We were taught the 4 B's at poly-tech. We didn't build it, we didn't buy it, we didn't break it so why the fuck blame us. Bastards. no 5.

I would not make the spindle an interference fit if you ever want to take it out again! I'm the same as Maylar, snug sliding fit and no movement anywhere when fitted. Original one did wallow out but replaced gearbox cradle 40 years ago and has been ok since. Nowadays I would use the Kegler clamps if I had problems.

I have never used the Kegler clamps and I'm wondering if they would work without drilling the gearbox tube
IE would the indent be enough to hold the pin tight?

baz said:

I have never used the Kegler clamps and I'm wondering if they would work without drilling the gearbox tube
IE would the indent be enough to hold the pin tight?

Click to expand...

That's what I did, definitely made a difference to the handling, I still used the 2 bolts, after getting the clamps on tight, but they bear directly on the cradle tube which I did not drill. The cradle tube being too thin is the issue so its hardly going to matter if its undrilled as it will just deform.

kommando said:

That's what I did, definitely made a difference to the handling, I still used the 2 bolts, after getting the clamps on tight, but they bear directly on the cradle tube which I did not drill. The cradle tube being too thin is the issue so its hardly going to matter if its undrilled as it will just deform.

Click to expand...

The other advantage I would see would be less of a chance of the oil leaking out

Nortoniggy said " I would not make the spindle an interference fit if you ever want to take it out again! "

It doesn't need to come out again. It has a constant supply of 90 oil is being fed to it. I know its getting lubed because the only exit for the oil is past the o rings, and it has to get through the Oilite bushes first. I top it up once a year and or before a big ride.

Do it once, do it right. That was done in about 1976.

A would also do what Kommando suggested, if I had to do something again.

baz said:

I have never used the Kegler clamps and I'm wondering if they would work without drilling the gearbox tube
IE would the indent be enough to hold the pin tight?

Click to expand...

If the spindle bore is not compromised then yes.
#
I could not find an alloy clamp that suited what I wanted so machined my own to suit width, OD and bore.
The spindle was a nice (unworn cradle bore) push fit but as soon as the clamp was easy seated the spindle could not be moved.
That is all that is needed (The reasons to Not use an interference fit are obvious or should be)

I added 8 mm SS grub screws anyway along with axial on the spindle set at 0.0006" initial via a brass shim on the D/S (The end caps needed slight adjustment to reset their clearance to the cradle)





The system is not that bad but as the factory found it needed some extra spindle support which was easily done to maintain longevity.
If you take a bar and one person holds the ends while another holds the same bar inside of them, the outer force can overcome the inner even at equal strength which might be why most swing arm pivot designs are the opposite of that. (It seems the extra engagement (cradle bore width) did not work across the board for whatever reason (Given some cradles wear and others do not (both my 750 & 850)

You could most likely use a lathe carriage jig and line bore the cradle tube using the chuck and tail stock or just find a better cradle and add the clamps and be done with it (Unless you like time consuming projects)

update: I obtained a + .005" shaft, had it precison ground to .8784" ( cost $50 at Blackies Grinding , Auburn WA https://www.blackiesgrinding.com/ , then bought an adjustable reamer set on E-Bay from India ( $50), reamed the last few tenths in the cradle tube to achieve a firm tap fit in the cradle and thumb fit in the bushes