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Swing arm spindle to frame fit

Submitted by david_broadbent on Mon, 26/02/2018
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Commando

Happily rebuilding the swing arm set up on my Mk2A and got around to refitting bushes and spindle this weekend.

First problem was the spindle will not go through the installed bushes! Sadly I didn't check this before I installed them in the swing arm, but I would guess they are about 5 thou undersize! The spindle measures 0.875" and the bush bore looks like about 0.870."

Then I looked at the spindle into the frame (gearbox plate) tube. Once again, the tube appears too small for the standard spindle - although not by much. My digital vernier calliper records 0.874 - (-0+0.0005") for the tube bore. I can only get the spindle in about 1/8" using a hide hammer - and then a slide hammer to get it out again - so it's too tight.

Is this usual? I understand that the oilite bushes can shrink when pressed into place and requre reaming. Anybody any experience of this? The frame tube interface is a mystery UNLESS it is the fact that it is bloody cold in my garage - and maybe I should be heating the tube up a bit to get the spindle in place?

Any suggestions?

Submitted by allan_walker on Mon, 26/02/2018

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Hi Dave,

I've not had the need to replace my s/a bushes or spindle, but a couple of general thoughts come to mind.

First of all, it's not considered a good idea to ream sintered (oilite) bushes. Apparently, the surface can 'smear' and prevent the oil from permeating the bush.

Secondly, I remember fitting a new s/a spindle to a 1950's Tiger 100. A drive-in fit which was made much easier by freezing the spindle overnight.

Having said all that, I understand that oversized Commando spindles are available for when the spindle holes in the cradle have worn. You haven't got hold of one of these, have you?

Submitted by david_evans on Mon, 26/02/2018

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Sounds like the bushes are the culprit, where did they come from? but the spindle should go into the cradle without too much hassle, so a combination of shite tolerances. Send them back to the supplier and get them to replace them with ones that fit.

Submitted by david_broadbent on Mon, 26/02/2018

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I wish I had tried the bushes on the spindle before pressing them into the swing arm!

It isn't an oversize spindle as it measures precisely 0.875" which is 7/8", which is what it should be. The spindle that came out is quite heavily corroded in places - and worn in others - but you can still find places that measure 0.875, which is why my first thoughts are the temperature in the garage (it is bloody cold). The old spindle took a lot of effort with a slide hammer to get it out, so I know it's likely to be tight. I cannot see how the shaft can be moved in situ to line up with the 1/4unf bolt!!!.

I have spoken to the kit supplier who has assured me that all the bushes are the same size, but that they can shrink depending on how they are fitted? Not sure how that would work ?

Submitted by alan_blackhurst on Tue, 27/02/2018

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The method I used was to heat the swinging arm the bushes then slid in with lots oily smoke. I then left them in a oil bath for 24hrs. The new swinging arm pin slid straight in without needing any mods

Submitted by alan_blackhurst on Tue, 27/02/2018

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The method I used was to heat the swinging arm the bushes then slid in with lots oily smoke. I then left them in a oil bath for 24hrs. The new swinging arm pin slid straight in without needing any mods

Submitted by martin_freeman on Wed, 28/02/2018

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Dear Dave,

See photo

I may have a solution to your problem, If you are near Doncaster you can pop over when snow melts and borrow it, not could post it for £3 on understanding you send it back within a month.

Bushes can easily change size when pressed in, as they can deform getting shorter and fatter, in your application swinging arm fixes outer diameter so they get smaller

Regards Martin.

Attachments 2018-02-28-16-23-25-jpg

Submitted by david_broadbent on Thu, 01/03/2018

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Previously Alan Blackhurst wrote:

The method I used was to heat the swinging arm the bushes then slid in with lots oily smoke. I then left them in a oil bath for 24hrs. The new swinging arm pin slid straight in without needing any mods

Thanks Alan, I shall be giving this a try. If nothing else I might get the workshop a bit warmer by doing it!

Dave

Submitted by david_broadbent on Thu, 01/03/2018

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Previously Martin Freeman wrote:

Dear Dave,

See photo

I may have a solution to your problem, If you are near Doncaster you can pop over when snow melts and borrow it, not could post it for £3 on understanding you send it back within a month.

Bushes can easily change size when pressed in, as they can deform getting shorter and fatter, in your application swinging arm fixes outer diameter so they get smaller

Regards Martin.

So the tool is a reamer made from an old spindle? Sounds a good idea. I intend to give Alan's idea a try first to see how I get on. If that fails I shall be in touch!

Thanks for the offer,

Dave

Submitted by john_neely on Tue, 06/03/2018

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If ou don't manage to fix it, there is a write up in an old Commando Service Notes that I have which Maybe of interest plus they list an oversize spindle. Part no 064077 not much use now though.

In my loft I have a 750 swing arm with rollerbearings each end brand new shame it won't fit my 850.

Submitted by david_broadbent on Wed, 07/03/2018

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Previously john_neely wrote:

If ou don't manage to fix it, there is a write up in an old Commando Service Notes that I have which Maybe of interest plus they list an oversize spindle. Part no 064077 not much use now though.

In my loft I have a 750 swing arm with rollerbearings each end brand new shame it won't fit my 850.

Not managed to get around to the job yet - so bloody cold in the garage! Just downloaded the Service Notesthough , my old set having been lost in the dim and distant. An interesting read as you say.

Your 750 roller bearing swing arm sounds fascinating. Do you have a photo? Sadly wouldn't fit my bike either!

Submitted by john_neely on Wed, 07/03/2018

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Yes I can take a picture just hope I can post it.

Where did you find the notes I could not find them in the library, were they upgraded I only ask as I have just purchased a non runner which will get my full attention soon.

Submitted by john_neely on Tue, 13/03/2018

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Dave

Just been in the garage loft and found the 750 swing arm with the roller bearing conversion and unwrapped it pictures attached I hope.Cool

Well just been bombed out a single picture was too large and don't know how to reduce them.

Submitted by lance_crossley on Tue, 13/03/2018

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Previously john_neely wrote:

Dave

Just been in the garage loft and found the 750 swing arm with the roller bearing conversion and unwrapped it pictures attached I hope.Cool

Well just been bombed out a single picture was too large and don't know how to reduce them.

Hi, John.

A bit off topic but if it helps I use Paint in Windows to reduce my picture size. Open up the picture in question then click on "Resize" at the top menu. Then click on "Pixels" to activate that element. You will have two figures in the boxes for Horizontal and Vertical. I usually amend the vertical one to 1,000 (the horizontal one will amend automatically to the appropriate figure) and then "Save as" with a different file name so I can keep the original image. I find this is usually sufficient to get your image small enough but if not you can always play around with lower pixel numbers till you get it right.

Submitted by tony_ripley on Wed, 14/03/2018

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Hi John,

If you have Paint 3D you shoud have paint. If you type Paint into the 'Type here to search' bar, does it find the paint app ?

I am assuming Windows 10.

Tony

Submitted by julian_wells on Thu, 15/03/2018

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Thanks for these very interesting pictures; two questions:

  1. Am I right in thinking that the housings for the bearings are larger diameter replacements for the tubes that would otherwise take the bushes?
  2. Your swinging arm spindle has a threaded hole for the standard silly 750 screw with to each side of it what appear to be slots for later-type cotter pins. My understanding is that current spindles from Andover Norton are "combination" items, but looking at the illustration in their online parts catalogue the slots appear to be at 90? from the threaded hole (at any rate, the slots are visible but the hole is not). Hence, what's the origin of your spindle?

Previously john_neely wrote:

If ou don't manage to fix it, there is a write up in an old Commando Service Notes that I have which Maybe of interest plus they list an oversize spindle. Part no 064077 not much use now though.

In my loft I have a 750 swing arm with rollerbearings each end brand new shame it won't fit my 850.

Submitted by john_neely on Fri, 16/03/2018

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I bought the swing arm many years ago it was advertised at the time as fit and forget, and have no idea where I got it from.

Shame I can fit it to the 850, I will take a look at it when I get down to it.

I will take a few more pictures.

Submitted by alan_throssell on Mon, 19/03/2018

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Previously john_neely wrote:

I bought the swing arm many years ago it was advertised at the time as fit and forget, and have no idea where I got it from.

Shame I can fit it to the 850, I will take a look at it when I get down to it.

I will take a few more pictures.

I too bought one of these back in the 1980's, they were displayed at one of the NOC National rallies (if I remember correctly) and I bought one on an exchange basis. I believe the company also ran a small advert in Roadholder at the time. I tried to track the company down about 19 years ago but couldn't find them (R.A.X. of Wolverhampton). I have had mine fitted on both my Commandos at different times and it has been very good in service. Still in use on my 750 Interstate. I did have the end caps spindle come loose a couple of times in use, so I had it "re-designed" to lock into position better. (Tightening the end caps sets the taper rollers for free play. So you don't want it coming undone!)

Regards, Alan

Submitted by julian_wells on Mon, 19/03/2018

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So -- an interesting period mod for someone (not me) to play with.

Previously Alan Throssell wrote:

Previously john_neely wrote:

I bought the swing arm many years ago it was advertised at the time as fit and forget, and have no idea where I got it from.

Shame I can fit it to the 850, I will take a look at it when I get down to it.

I will take a few more pictures.

I too bought one of these back in the 1980's, they were displayed at one of the NOC National rallies (if I remember correctly) and I bought one on an exchange basis. I believe the company also ran a small advert in Roadholder at the time. I tried to track the company down about 19 years ago but couldn't find them (R.A.X. of Wolverhampton). I have had mine fitted on both my Commandos at different times and it has been very good in service. Still in use on my 750 Interstate. I did have the end caps spindle come loose a couple of times in use, so I had it "re-designed" to lock into position better. (Tightening the end caps sets the taper rollers for free play. So you don't want it coming undone!)

Regards, Alan

Submitted by david_broadbent on Wed, 21/03/2018

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It's probably time to bring this thread to a close seeing as I have the bike back together now. Although the roller bearing swing arm is worthy of its own thread I would think?

So - I removed the undersized bushes - and discovered traces of powder coat in the bores of the swing arm. Cleaned that out and, after heating it up, slipped in the chilled bushes. Lots of smoke - but spindle still wouldn't fit afterwards! Recognising that the fit of spindle to bush is what the whole job depends upon, I took the swing arm and spindle to a local old school engine builders; Bill Bannister Engines in Bamber Bridge, Lancashire and Bill reamed the bushes for me and ensured a beautiful fit.

I then went home and made up a polishing stick of about 3/4" diameter, with a split down one end to take a length of emery paper. With the rod in the electric drill, I was able to polish out the offside end of the tube in the gearbox plates. It was all it took to allow the spindle to be slid in with just a few taps of a hide mallet. (Smug mode)

Next job was to fit the split collars I had machined up from a metric size stock item I bought. I did think about going the whole hog here and drilling off the frame tube and the collars to introduce a bolt to bear on the flats of the later spindle but decided against it.

In the first instance, when I nip up the collars the spindle is dead solid in the frame tube. No movement. No need for further work. In the second instance though, I never really liked the idea. The flats on the spindle are designed to take a pair of cotter pins, which is a recognised engineering solution to stop rotation between, for example, a crank and a pedal. I had lots of experience with those as a young lad and, in my experience they work really well when put together as intended - but hardly at all if you try to bodge it - like just sticking an ordinary bolt through the pedal. Hopeless. You need the flat of the cotter pin tight up against the flat in the spindle, no free play, dead tight and secure. In order for the spindle to move then it has to crush the cotter pin. Simply bringing the end of a bolt to bear on the spindle flat is not going to be anywhere near as effective. So I decided against doing it. Time will tell.

Finally I have also replaced the end caps with proper sized ones I made incorporating an M6 threaded rod through the centre. I have also done away with the grease nipple and replaced it with a hollow bolt in way of the 1/4 UNF lock bolt which has a plastic tube attached and will henceforth be my filler and sightglass for swing arm spindle lubrication! (see pic - hopefully)

I am very pleased with the result and can't wait to get the thing back together and out on the road. It will feel better - the old swing arm bushes were well knackered - and hopefully the lubrication sytem mod will ensure a long and trouble free service life!

Thank you all for the many helpful comments provided along the way.

Dave

Attachments img_2542-jpg

Submitted by david_broadbent on Mon, 16/07/2018

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To add a post script to my earlier note: The bike is back together and totally transformed after its major rework over winter. The only regret is the lubricating mod on the swing arm. Whilst I'm sure it works wonderfully well, it brings new meaning to the concept of total loss lubrication. The oil in the sight tube simply represents an extra reservoir to supply the swing arm with even more oil to leak out between the inner faces of the swing arm and the outer faces of the gearbox plates. I now have an ice cream tub to place under the bike every night. During this recent spell of very hot weather, quite a puddle formed under the bike one night!

I think at some future date I would research the availability of X rings, which are like rubber O rings but have a cross section like a letter X, and may improve the swing arm sealing situation. Over this last winter though I was unable to find a UK supplier for those but hopefully that will improve with time.

 


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