Low friction fork bushes

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Esmerela

Esmerela

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Just sharing a project. I bought a length of 50mm Delrin AF for this project last year thinking It would make a good winter job. I had a weeping seal so the forks were coming apart at some point during the off season then, my t160 decided to seize on the centre cylinder consequently the front fork job got put on hold.
Low friction fork bushes


Now we are on lock down T160 motor is rebuilt, it's time to spread the love to the neglected Mk3 in my life;) where did I put that piece of Delrin AF ?
Dupont added Teflon PTFE fibers to the resin for the AF grade, application Bearings, bushings, cams, and other anti-friction devices where extra toughness is needed.

I cut the of Delrin in half measure up the fork stanchions and the sliders quite some variation in size so I opt to machine in matched pairs for each fork leg.

Low friction fork bushes


I was surprised how well the material machined.

Low friction fork bushes


I fitted a 0.5mm shim above the upper bush to protect the top face when I assembled the forks. on test they work really well giving smooth linear motion to the front forks working well with my other fork modifications 1" over ground finish stainless steel 10mm damper rods and modified damper caps and internals I run 190cc 5wt fork oil . Combined with Ikon baics on the rear the bike is handling like a dream keeping the smile on a back road scratcher's face.
 
Nice stuff, giving me some ideas!

Curious, did you consider turning down extended length bushes?
 
Tell us about the T160....
What is the history?
Rod bearings?
Oil filter?
 
acadian said:
Nice stuff, giving me some ideas!

Curious, did you consider turning down extended length bushes?
Click to expand...

Hi
To be honest after reading numerous post on this forum over the years I believe the jury is still out on the effectiveness of the RGM type extended bushes. I did make replacement valves to take out some of the slop in the damper and I also made the damper valve seats with two flats and not the std four this makes a big increase in rebound damping (hence the 5wt oil) and adds a little compression damping. I don't have the top-out clank however I would like to add a top-out spring inside the the damper tube but I have not found anything suitable.
 
Esmerela said:
Just sharing a project. I bought a length of 50mm Delrin AF for this project last year thinking It would make a good winter job. I had a weeping seal so the forks were coming apart at some point during the off season then, my t160 decided to seize on the centre cylinder consequently the front fork job got put on hold.
Low friction fork bushes


Now we are on lock down T160 motor is rebuilt, it's time to spread the love to the neglected Mk3 in my life;) where did I put that piece of Delrin AF ?
Dupont added Teflon PTFE fibers to the resin for the AF grade, application Bearings, bushings, cams, and other anti-friction devices where extra toughness is needed.

I cut the of Delrin in half measure up the fork stanchions and the sliders quite some variation in size so I opt to machine in matched pairs for each fork leg.

Low friction fork bushes


I was surprised how well the material machined.

Low friction fork bushes


I fitted a 0.5mm shim above the upper bush to protect the top face when I assembled the forks. on test they work really well giving smooth linear motion to the front forks working well with my other fork modifications 1" over ground finish stainless steel 10mm damper rods and modified damper caps and internals I run 190cc 5wt fork oil . Combined with Ikon baics on the rear the bike is handling like a dream keeping the smile on a back road scratcher's face.
Click to expand...
Nice job Esme. How much was that chunk of Delrin ? I understand it's pretty expensive.

Looking forward to the Trident story too.

Cheers,
cliffa.
 
Hi Cliffa

I paid £60 o_Ofor 50mm x 300mm Delrin AF, as you say not the cheapest. I could have made them from Delrin/Acetal for £25. However I had read about the Delrin AF and wanted to give a try.
 
Esmerela said:
Hi Cliffa

I paid £60 o_Ofor 50mm x 300mm Delrin AF, as you say not the cheapest. I could have made them from Delrin/Acetal for £25. However I had read about the Delrin AF and wanted to give a try.
Click to expand...

Where did you end up in terms of clearance fit with the AF? Just so I have a number to aim for if I try this myself
 
acadian said:
Where did you end up in terms of clearance fit with the AF? Just so I have a number to aim for if I try this myself
Click to expand...

Hi acadin

Sorry I can't give you a number. I worked to size with my digital caliper and a slection of fork original bushes, then I removed the tailstock /footstock and just kept nibbling until they fitted the slider or felt good on the Stanchion. There are figures quoted in the technical data section of the manual.
 
I find this interesting, does anyone here (pref. in the EU) make and sell sets of these bushes? Or can you buy a set from somewhere else?
 
Maxton in the UK use Delrin for fork bushes too, so I think you chose your material wisely Kate!

Fiatfan, it may be worth asking them as I’m not sure if they sell them off the shelf. My only experience with them is when they make them to suit individual applications when doing fork rebuilds and conversions, etc.
 
Esmerela said:
Sorry I can't give you a number. I worked to size with my digital caliper and a slection of fork original bushes, then I removed the tailstock /footstock and just kept nibbling until they fitted the slider or felt good on the Stanchion. There are figures quoted in the technical data section of the manual.
Click to expand...

Same here, the OEM bushes were made to mass production tolerances of the day and also the clearances looser than today's Fork standards to reduce stiction. So by changing materials to low friction you can close the clearances up but you are still left with the stanchions and fork sliders wide tolerances, so each bush is best machined to suit the parts they will be fitted to. So I do the same when machining the bushes, helped by a DRO setup so I can take very small incremental cuts when I get close to the finished size.
 
Probably best to run these things up after going for new stanchions?
 
kommando said:
Yes, there is no wear in a new stanchion and the wear should be less with a lower friction and softer material bush.
Click to expand...
I'm not seeing wear on the stanchions when using non metallic bushings. I started out with modern teflon impregnated fork bushings but the teflon wore down to the metal and I was back to metal to metal wear. Nylon also shows wear and UHMW doesn't machine well. Delrin machines well but is not as slippery as teflon and can "stick/slip". Delrin AF is an improvement over plain delrin to get around the stick/slip problem. But the best material is Turcite. They use it on heavy machinery linear bearing surfaces to both avoid friction and wear. I'm not seeing wear on slippery Turcite bushings. But its expensive and its thermal expansion properties require careful machining and design. The bushing must be slit so they can expand with temperature and not bind up. I know someone who made turcite fork bushings without the slit and they had chatter problems because they tightened up.

check out this site:
www.aetnaplastics.com

Turcite® | Aetna Plastics

Turcite® is an internally lubricated, acetal-based material (with properties similar to those of Delrin AF) designed for applications with demanding wear and friction requirements. Turcite® creates...
www.aetnaplastics.com
 
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