Race frame

[Scooterlam]

starting work on my proddy racer, just found the lower race is cracked.
is it just a case of heating the steering tube and drifting out the old.
if so where do I get a replacement.

[foremanbob]

Yup.... heat and force to chap it out.... chap it out from inside the fork tube though...


Scooter resto's stuff is as good as any... recently fitted a Scootopia one to a mates scooter, nice quality item, but the sleeve that goes inside the fork tube was twice the length of the one that came out....

Plenty of heat going back in too....

[Scooterlam]

thanks,
is the top "Bung" the same, I'm shortening to take GP panel work and forks.

[Knowledge]

No. the top of the tube is machined to suit the upper bearing race. When you cut an inch off the fork stem, you cut off this machined section and are left with a tube that is too narrow for the original bearing race.

This is a problem, but there are solutions.

You can use the smaller top bearing race from the chrome ring and machine a spacer between the tube and the smaller bearing race. Alternatively, you can buy one of the new tapered bearing conversion from Ian Frankland, which offers an option for this specific scenario.

[Jim Rose]

How do I get in touch with Ian Franklin for the tapered bearing? Ideal for my project

[Digger]

How do I get in touch with Ian Franklin for the tapered bearing? Ideal for my project

He's on FB...

[Jim Rose]

How do I get in touch with Ian Franklin for the tapered bearing? Ideal for my project

He's on FB...

I'm one of those who doesn't facebook.

Thanks Martin/knowledge i've just ordered the tapered bearing and those for the links.

[Fast n Furious]

Just be wary about some of these lower bearing kits. Some of them on the market are machined slightly oversized making them a right bitch to install in the steering tube irrespective of how much heat you use first. If you have to really force it in, there is a risk of it getting damaged and in some cases it can split the bottom of the steering shaft tube. Use some micrometers or digital verniers to measure the diameter of the stub. (I have a figure of 42mm in my head but I haven't checked this) It may need machining back in a lathe if it is slightly oversized. If the old bearing cup comes out using only reasonable force using methods as described in Sticky's manual then you can use the old cup as a guide as to what the diameter of the stub should be.

I did my own conversion on the lower bearing to taper roller. I don't have details to hand, but basically the bearing assembly was a wheel bearing as used on most road trailers. I then had to make a new outer bearing housing with stub to insert into the steering tube. In order to get the bearing down the fork steering shaft I had to remove the steering stop plate on the forks carefully with a grinder. Before doing this however I drilled and countersunk two holes through the plate so that when the plate was removed I could tap the holes I had made in the fork shaft ready to accept 2 short countersunk screws to reattach the plate to the shaft after the new lower taper bearing was fitted. If you do this, make sure the screws are high tensile and short enough so they don't foul the speedo cable.
Alternatively you could weld the stop plate back on because this bearing probably won't need replacing for another 40 years!

[Phil D]

Hi F & F
Just reading with interest your post about lower bearing race upgrade to taper bearing .
Would it be possible to use the old bearing race to house the new taper bearing .
It would save some work.

[gizmo]

No. the top of the tube is machined to suit the upper bearing race. When you cut an inch off the fork stem, you cut off this machined section and are left with a tube that is too narrow for the original bearing race.

This is a problem, but there are solutions.

You can use the smaller top bearing race from the chrome ring and machine a spacer between the tube and the smaller bearing race. Alternatively, you can buy one of the new tapered bearing conversion from Ian Frankland, which offers an option for this specific scenario.

That's interesting knowledge about the top race conversion. How does that work then?

[Knowledge]

Gizmo,

I will be doing the conversion over Xmas, so I will take some photos and post them up on here, but meanwhile I will try to explain in words. It does involve some mistreatment of a chrome ring though, and people of a sensitive nature might wish to look away now.

I have undertaken this work on chrome-ring scooters when I have converted them to GP spec.
1. Remove the chrome ring with the top race in place.
2. Cut the inch off the top of the stem to give the GP/DL length of tube.
3. Remove the halo from the chrome ring, but leave the lug that acts as the stop for the steering lock
4. Carefully measure the ID of the cut-down steering tube. Measure twice, cut once.
5. Put the remainder of the chrome ring into a lathe and turn-down the OD of the chrome ring, to create a spacer, but leave a flange on the top so the remainder of the chrome ring doesn't slip down the steering tube.
6. Slot this into the top of the steering column tube with a nice, tight interference fit with the upper bearing track in place.

If you don't have a chrome ring to hand, find a section of tube that is the right dimensions, and make your own spacer from scratch, though you will have to fabricate your worn lock-stop too.

I hope this is helpful

[gizmo]

Gizmo,

I will be doing the conversion over Xmas, so I will take some photos and post them up on here, but meanwhile I will try to explain in words. It does involve some mistreatment of a chrome ring though, and people of a sensitive nature might wish to look away now.

I have undertaken this work on chrome-ring scooters when I have converted them to GP spec.
1. Remove the chrome ring with the top race in place.
2. Cut the inch off the top of the stem to give the GP/DL length of tube.
3. Remove the halo from the chrome ring, but leave the lug that acts as the stop for the steering lock
4. Carefully measure the ID of the cut-down steering tube. Measure twice, cut once.
5. Put the remainder of the chrome ring into a lathe and turn-down the OD of the chrome ring, to create a spacer, but leave a flange on the top so the remainder of the chrome ring doesn't slip down the steering tube.
6. Slot this into the top of the steering column tube with a nice, tight interference fit with the upper bearing track in place.

If you don't have a chrome ring to hand, find a section of tube that is the right dimensions, and make your own spacer from scratch, though you will have to fabricate your worn lock-stop too.

I hope this is helpful

That explains it fully knowledge, thank you. You should write a book or do a magazine article

[Fast n Furious]

Hi F & F
Just reading with interest your post about lower bearing race upgrade to taper bearing .
Would it be possible to use the old bearing race to house the new taper bearing .
It would save some work.

Ahh. If it were that easy Phil then it would have been a popular conversion years ago. Sadly, the old bearing cup has to go and a new cup needs to be made from mild steel so it can accept the loose outer taper shell of the new taper bearing assembly. I should have drawn this up when I did it, but its a straight forward job for a machinist if he has the old cup and the new taper bearing. You can dispense with the dust seal shield as the new bearing has a built-in oil seal.
I wish I'd done the same to the top bearing but that requires additional work to the top of the fork columb, which will probably mean that you can no longer use a traditional speedo cable and may need a collar making so you can still clamp the headset bracket on. There are ways around this but they involve more exotic adaptions.

[Phil D]

Hi F & F
Just reading with interest your post about lower bearing race upgrade to taper bearing .
Would it be possible to use the old bearing race to house the new taper bearing .
It would save some work.

Ahh. If it were that easy Phil then it would have been a popular conversion years ago. Sadly, the old bearing cup has to go and a new cup needs to be made from mild steel so it can accept the loose outer taper shell of the new taper bearing assembly. I should have drawn this up when I did it, but its a straight forward job for a machinist if he has the old cup and the new taper bearing. You can dispense with the dust seal shield as the new bearing has a built-in oil seal.
I wish I'd done the same to the top bearing but that requires additional work to the top of the fork columb, which will probably mean that you can no longer use a traditional speedo cable and may need a collar making so you can still clamp the headset bracket on. There are ways around this but they involve more exotic adaptions.

Thanks F&F
It seems a worthwhile mod especially if the bearing cones are shot and need replacing anyway.
I was surprised when I saw the original bearing set up as it is basically from a pushbike
I forgot to ask what you made the new cup out of but you've answered that as well
I often use a local engineering shop for jobs like this,the owner and head engineer always jokes he never makes any money on these little "one offs" because of the time it takes to set up etc.
I am lucky though having a friendly machine shop down the road has been a godsend on several occasions.
If anybody wants work doing that they are unable to do themselves due to not having the skills or equipment required visit your local shop you may be pleasantly surprised