Honing fork sliders?

[Chris Stevens]

I need to weld some tabs for front brake caliper onto trials bike fork sliders, which are from bikes which originally had drum brakes. Obviously no matter how careful I am doing the welding, some amount of distortion is going to occur.

Wonder if anyone has any bright ideas on how to deal with the distortion? Only thing I could think of was some sort of small cylinder hone, taking things very slowly with plenty of coolant.

 

[ronan]

A tight fitting piece of solid steel bar smeared with copper grease pushed down the bore ? To prevent distortion i mean.

 

[Bill Edwards]

My mental picture of this is that the distortion you're concerned about will be moving the calliper out of square with the disk? Like two tabs onto a piece of tube or whatever which will get a weld on each side?

 

[roofman]

weld bigger tabs that you need then machine them to a matching pair once welded on

 

[Chris Stevens]

A tight fitting piece of solid steel bar smeared with copper grease pushed down the bore ? To prevent distortion i mean.

Yes that would be worth trying, but I get the feeling its still going to distort a little anyway? This is for a bike I am doing some development work on, and have tested completely new rear shock today, which has made rear suspension work a good deal better..........

 

[BrokenBiker]

My mental picture of this is that the distortion you're concerned about will be moving the calliper out of square with the disk? Like two tabs onto a piece of tube or whatever which will get a weld on each side?

i thought the same, i would be more concerened with the tabs staying put than the tube distorting.

weld bigger tabs that you need then machine them to a matching pair once welded on

this was going to be my suggestion also, ended up doing similar on my CBR for an aftermarket fairing, the firs tlot of brackets twisted a bit and notihgn fit properly so had bigger tabs put on and then filed them to size with a lot of measuring

 

[Chris Stevens]

Problem here is not the tabs twisting, its distortion of the inside of the fork slider, which prevents the slider moving freely over the stanchion. I can make a heavy duty fixture which mounts to wheel spindle hole, which should keep tabs pretty well aligned, but cant work out the best way of honing inside surface of slider in weld area? These bikes all have drum front brakes, and wheels have "Z" spokes, so its a good idea to convert to a modern wheel with disc brake.............

 

[the snooper]

Problem here is not the tabs twisting, its distortion of the inside of the fork slider, which prevents the slider moving freely over the stanchion. I can make a heavy duty fixture which mounts to wheel spindle hole, which should keep tabs pretty well aligned, but cant work out the best way of honing inside surface of slider in weld area? These bikes all have drum front brakes, and wheels have "Z" spokes, so its a good idea to convert to a modern wheel with disc brake.............

i think it you will struggle to keep / get the bore perfect after sticking that much heat into it, id be inclined to fit another front end

 

[ronan]

If you take your time and don't put too much heat into the slider, using the bar as i mentioned above, you could ream or turn the distortion out of the slider and turn up oversized fork bushes.

 

[ronan]

Also Chris, what bike are the forks off ? Would the sliders be up to the extra stresses that a disc brake would inflict on them ?

 

[mike os]

Unless you get it seriously hot I don't think it will be an issue, end of the day it is 2 point contact. .. Bush at one end and bolt at the other I guess?

 

[mike os]

Fill it with water?

 

[graffian]

A a long[extended] floating reamer with a guide behind it. david brown or cogsdill reamer.
But I don't recall it being a problem, I had tabs welded on Trumpet front ends by a
mate who worked at Dennis, first leg he did I got it back after he had welded the tab on
I rode home wondering how I was going to ream them, the bush still slid up and down;-)

 

[Chris Stevens]

Thanks for replies.............some useful ideas! Forks are from a TY Yamaha trials bike, and it would certainly be easier to fit complete front end from later bike, which are cheap and easily available, and work better than older forks.

Unfortunately though due to financial interests of those behind the only serious British championship series for older bikes, parts like used modern forks are forbidden, but curiously modern recently produced "P65" frames, wheel hubs, forks, yokes, etc etc, are all allowed.

Earlier model TY Yams had drum brakes, the last ones discs, so want to modify the forks to take a disc caliper and fit a modern front wheel. Drum brakes were ok back in the day, but 4 pot caliper is a lot better and with used parts disc conversion will probably cost less than re-spoke of std wheel.

 

[addjunkie]

Id fill the leg with oil. Buy the time the leg and oil have heated enough to do damage the weld will have cooled.

 

[ronan]

Thanks for replies.............some useful ideas! Forks are from a TY Yamaha trials bike, and it would certainly be easier to fit complete front end from later bike, which are cheap and easily available, and work better than older forks.

Unfortunately though due to financial interests of those behind the only serious British championship series for older bikes, parts like used modern forks are forbidden, but curiously modern recently produced "P65" frames, wheel hubs, forks, yokes, etc etc, are all allowed.

Earlier model TY Yams had drum brakes, the last ones discs, so want to modify the forks to take a disc caliper and fit a modern front wheel. Drum brakes were ok back in the day, but 4 pot caliper is a lot better and with used parts disc conversion will probably cost less than re-spoke of std wheel.

Are you into pre-65 trials Chris ?

 

[Chris Stevens]

Are you into pre-65 trials Chris ?

No thankfully not! The idea of "P65" trials here in the UK is thinly disguised modern bikes fitted with dreadful old Brit motors from things like Cubs and Bantams, which cost £6-15k and maybe are perfect for those with more money than sense!

Sadly though these modern machines mean anything vaguely authentic is no longer competitive, and either remains unused, or worse still is broken to build a modern bike.

 

[Pete.]

Don't stanchions slide on bushes in the slider, rather than the slider itself? All the ones I ever had apart did.

I don't see this being a problem really. I would find a crappy fork leg and give it a go.

 

[Chris Stevens]

On trials bikes there are generally bushes on the bottom of the stanchion and top of slider, or stanchions run direct in the sliders.

 

[Mr shiney]

I have welded caliper mounts onto sliders loads of times. It's a common mod for one of the bikes I restore. Never had one distort yet. Aluminium is very forgiving, just work slowly.