Prewar headraces

[nickg]

Me again.

Stripped the forks and the head-races are, unsurprisingly, worse for wear.

OD 40.4mm 1.59"
ID 26.7mm 1.05"
Balls 4.4mm dia.

I toyed with trying to clean them up in the lathe on a mandrel but the photo shows hairline cracks on one race, perhaps from previous fitting or removal (they fell out this time!).

Wondering what the options are:



1. Find ones that fit? Anyone making them?

2. Try mountain bike ones with a bit of sleeving and grinding? Size is tantalisingly close. Can they be any less durable than the originals??

3. Make new ones - beyond my ability - special steel, hardened and tempered without distorting :-(

[CPR]

Hi Nick
I had a similar problem to you with the headstock ball races on my 1935 Cotton 250 Twin Port JAP. I also came to the same three conclusions as you.
First I went for the second option, the mountain bike bearings. The headstock on my frame had two internal diameters. The inner smaller one, being the one the original bearing race fitted. I found that the mountain bike bearing only fitted the the larger outer diameter, which had a thinner diameter circumference of metal, being on the end of the headstock. The mountain bike bearings were of a smaller diameter and although caged, I did not think they would be strong enough to stand the speeds/rough roads they would encounter.
This left me with the first option, ie. looking for suitable ball races at autojumbles. Eventually, I did find some that fitted quite closely, albeit with a little modification.
The mods I carried out were to grind the thickness down a little to get the race to sit further up the headstock. I also ground out the internal diameter to give more clearance for the fork tube. As the ball race was unused ( N.O.S.) I lapped the race with spare ball bearings and grinding paste. I’m not sure if I had to grind the outer diameter or not. I used a medium strength loctite to secure the ball race in the frame. I also filed two small slots on the shoulder in the headstock, where the ball race locates. This hopefully, will make any removal of the ball race easier.
To remove indentations in other ball races, I spun them up in the lathe and used a steel rod wrapped with emery cloth to smooth them out. I then lapped them out with ball bearings and grinding paste. It did the trick.
Somewhere, I have a similar spare unmodified ball race, but can not find it at present (I’ve put it in a ‘safe place’ !! ) If you need it, I can have another look for it in the new year.
The person I bought these ball races from usually has a stand at the VMCC autojumbles at Shepton Mallet (Not at the Bristol Bike Show) I’ve also seen him at Paul Powell’s jumbles at Bridgwater.
Hopes this helps.

Chris R.

[cottonjo]

Unsurprisingly, Alan Freke has used mountain bike head race bearings too.
Paul

[nickg]

Thanks Both

If you find the races and don’t need them as spares then I’d be interested Chris.

Stumbled across these today:

www.motorcycleproducts.co.uk/steering-head-ball-bearing-kit-013064/1/013064

Worth a try at the price and claim to be motorbike not bicycle bearings.

Thinking a carbide tip might work to take a couple of mm off OD in lathe.

All the best for 2023.

Nick

[johnc]

Nick, I just had a look, and found a bearing that fits your measurements. its strangely cracked at the edge, and I'm wondering if with such a large rake angle/ offset, there is a lot of load on one part of the bearing, and little load on the other side
how do I add a pic???   

Attachments:

[nickg]

Hi John, I’m wondering if the state of the head races explains your cornering experience at Cadwell Park :-)

Lots of fine cracks on the races, I didn’t spot them until I took a photo! Also Brinelling.

When I assembled the races with balls there seems to be little or no lateral restraint.

As we discussed on the phone, my BMW R60 had the handling transformed by new head stock bearings despite no obvious play and 10 MOT passes.

Conversely the Panther had knackered bearings and new ones made no difference!

Have ordered some cheap races to see if I can machine them.

[nickg]

Still work in progress but the races I found machined OK with a carbide tool. But not convinced the cup and cones I have tried have much axial restraint. 

Got a single MTB bearing from Simply bearings that will need sleeving rather than machining (tricky). No play even without pre-load.

Will be a while before I can report back on performance, what could go wrong!

[nickg]

Update

So my first attempt didn't feel very good in terms of lateral restraint although the races looked very similar to the ones that were in.

I have now modified and fitted cheap pit bike cones from Ebay but with loose balls as the cages wouldn't fit over the spindle. These have a more pronounced cup and cone profile as opposed to simple thrust bearings.

Not road tested but feels much better with free movement and no play.

Made a new top housing from some SS I had.

Added grooves for bearing removal as Chris suggested.

One mistake was to make the top bearing a press fit in the new top housing, wish I'd gone sliding + Locktite, will probably have to Dremel it out if I replace it.

Hope this helps someone or inspires a better solution.

Did look at taper roller but couldn't find anything close on size and are difficult to machine.

[nickg]

A couple more pics. Machining of the top housing isn't as rough as it looks, greasy prints not chatter! The cone race in the housing looks like the one on the bottom yoke so wouldn't be held in the original housing.

Had to bore out the races using small cuts and carbide tool, not much meat left so will see how they survive. I should have splashed out another £7 and got 2 sets as one has a tiny bit bigger hole (one I used for bottom yoke) so had more metal left at the inner lip once bored.

"PIT BIKE HEADSTOCK BEARINGS 41mm/22.5mm & 41mm/24mm fits 110cc 50cc PITBIKES"

Obviously, don't try this at home etc . . .

[cottonjo]

Many have struggled to make a fine engineering job of the steering head races. As you say there is not much material to work with. Yours look pretty good. Even in the early days some were damaged simply by over tightening the adjustment.
Well done
Paul

[nickg]

Thanks, always a risk with these things that after hours of work someone posts a link to direct replacement for £20 :-)

These were what I got, I'm sure others may be even better:

You can see in the photos there is still a bit of meat on the bottom cone despite boring a bigger hole so worth getting 2 sets and use the larger holed ones. Not much to take of the OD of the cups unlike the others I tried.

I bored a step in the bottom cone to register on the step in the spindle which I tidies up in the lathe first. Only a small Warco lathe.

Abandoned the cage and used 21 balls held with grease.

Original top housing could be adapted or perhaps cone could be set in epoxy??

Got other issues now, will start another thread!! Handlebars.