FF: Forks FF3 Bottom link assembly dimension

[Cyborg]

Can anyone tell me what the dimension is supposed to be between the two large eyes of the FF3 bottom link assembly? I want to make a gage to use while straightening the arms. The idea being … use a piece of 1.750” solid bar with ends machined parallel so it will tell me if the eyes are the correct width and parallel. I machined some temporary bushing to fit in the large eyes so I can (eventually if all goes well) slide a spindle through there to confirm alignment. It appears both arms are twisted slightly, but with the gage set on V blocks (and the other end of the link mounted on a spindle set on another pair of V blocks) it should help confirm if just one is bent or both. Any suggestions, recommendations etc would be welcome.
Thanks in advance.

 

[chankly bore]

4.420" bare. .292" out from front FF6 register, bare; measured with a straight edge on the large eyes. Somewhere on the Forum I believe Clevtrev gave all dimensions, but these are the only ones I've noted.

 

[Cyborg]

Thank you for that. I tried searching on the forum, but only got some discussions about them being bent and needing repair. I’ll have another look.
I just measured mine. At the rear of the eyes it’s about 4.531 and at the front it’s 4.599 so pigeon toed. When I slip a spindle though the bushings I made, the misalignment of the spindle ( it won’t go through both bushing) tells the same story. Eyes bent outward.
Maybe with a bunch of heat, I can use the solid bar and the press to get it bent back at least part way. Remove the bar and use the press to get it the rest of the way…. until the bar just slips in and the eyes make contact all the way around. Sounds simple…. as long as it doesn’t squirt out of the press or I set the garage ablaze.

 

[timetraveller]

I have had to check and straighten several tens of these while supplying the JE steering stems. Despite all the stories of them being forgings, immensly strong etc I find that they will bend easly by hand and the use of some leverage. The large diameter spindle you have made will do the job easily. Hold the front of the link in a solidly mounted vice, or similar, and just try tweaking it. I think you will be surprised just how easily it moves. Be careful not to distort the eyes and keep at it until your oversized spindle will slide easily through both eyes at the same time. Go at it gently to start with until you have learnt just how easily it moves or you might have to start and reverse some of the bending.

 

[Robert Watson]

TT is right. I have straightened 2 or3 of these, never required any heat, just go gently and tweak a bit at a time until all is lined up.

 

[greg brillus]

The picture everyone is looking for......go to thevincent.com look up Comet page, then go to Girdraulic forks........The linked picture is there with all the dimensions........ I think the specs given by our Trev........

 

[davidd]

David

 

[Cyborg]

Thanks everyone. Good to know it doesn’t require the torch. Someone has been at it in the past, at least it looks like some heat has been applied along with a bit of a beating. It actually doesn’t look that bad, so hopefully it will come into line without any drama. When pressing in the temporary bushings, one eye seemed like it might be out of round by a couple of thousandths, but I haven’t measured it with the bore gauge yet.

 

[timetraveller]

If the eye is distorted then the easiest and cheapest way is to clean it up and make an oversized Oilite bush.. The alternative is to bore it, bush it back to standard and then fit a standard Oilite bush. The best is to use Greg's mod of using ball races or needle roller bearings on each side but that is a whole different can of worms.

 

[Cyborg]

I just turned the gage block to the final dimension 4.420” within .001” which is pretty close give my talent level and the relic I’m using to turn it. The micrometer carriage stop is probably from the 30’s. I’m still thinking that I could get it at least part way to where it should be by using the press. I can’t overshoot the target that way. If the “F” dimensions in Trevor’s diagram aren’t exactly equal, I’m assuming (within reason) I can compensate for that with the shims that go next the eccentrics. I think I have that straight in my head?
The bearings had crossed my mind, but unsure if I want to head down that road. Like you say…best method, but time is the major factor. I actually plan on riding this one. I still haven’t measured the eye. Figure I’ll go with getting the thing straight first. It doesn’t seem to have munch in the way of twist so that’s good.