Chain rubbing block ideas and UHMW tape for swingarm protection

[gcloys]

During my sprag do, engine out, I decided to sort the broken tab for the chain rubbing block. The chain had eaten into the frame mount and I'm sure it had been that way for a while.  When I acquired the bike, I wrapped the mount in uhmw cutting board (sheet) from the dollar store.
  Gleaning all the info I could from the various boards, I assembled quite a portfolio of pictures showing the hacks people have done over the years. This is my contribution to the knowledge base. The frame mount is a handy 1.25" so there are lots of possibilities. These clamps ($10 for 2) for mounting lights on ATV etc. are 1.25" and the hole is perfect for an 8mm counter sunk bolt through a 1/4 sheet of uhmw cutting board, cheap found anywhere.
The main concern is how it will effect the frame mount during catastrophic failure of the rubbing block.  The OEM would break the weld and disappear, usually with the rider thinking what was that noise? I was concerned the clamp would torque the mount if too tight, but the clamp assembly is aluminum and would probably fail before damage to the frame. I left it a tight but not super tight so it would spin the clamp and the chain would eat into the clamp as a fail-safe. Cut the board to length so it holds the chain where a new rubbing block would, 1/2 inch past the end of the clamp and enough to hood the bolt on the sprocket side..
The only downside to this set up, using this set of clamps, is you must remove the sprocket cover to fit the screws. It could easily be drilled and tapped, but it isn't a big a job once the oil is drained. So far all is well. There are lots of variations of the clamps.  The other idea is using a uhmw split shaft collar with 1.25 bore. Should be easy on and off and last for years.  As for the top of the swing arm where there is no rubbing strip but there is sign of chain slap/rub, I use UHMW tape. The last pic. is a bedframe hanger modified to use the top foot mount bolt.  No molesting the frame but doesn't protect the frame mount. Catastrophic failure should happen at the bolt but risks fouling the chain. It could be secured to the subframe,
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[ssevy]

So happy I found this thread!
I found some 1.25" light brackets on Amazon that have a hinge and a mounting screw which is tightened from the bottom, so that should make it easily replaceable without having to remove the sprocket cover. I got a sheet of UHMW 3/4" thick as well, which I can make any width, and actually have the bracket embedded up underneath it to make it less apt to be ripped away.
Can you tell me how thick you needed to make your UHMW, and your width as well? I could not really tell from the pictures. I was also going to use a screw and some JB Weld to attach the plastic to the bracket surface to keep it in place.
Any other considerations that I have missed?
Many thanks!

[gcloys]

So happy I found this thread!
I found some 1.25" light brackets on Amazon that have a hinge and a mounting screw which is tightened from the bottom, so that should make it easily replaceable without having to remove the sprocket cover. I got a sheet of UHMW 3/4" thick as well, which I can make any width, and actually have the bracket embedded up underneath it to make it less apt to be ripped away.
Can you tell me how thick you needed to make your UHMW, and your width as well? I could not really tell from the pictures. I was also going to use a screw and some JB Weld to attach the plastic to the bracket surface to keep it in place.
Any other considerations that I have missed?
Many thanks!

Sorry for the late reply. I only used 1/4 thick and 1 1/2 inch (33.4mm) wide and about 3.5" (87.5mm) long for mine.  The bracket I used had a hole for mounting that fit an 8mm bolt perfectly. I used a bolt with a countersunk head so not to foul the chain. 
  Could you post a pic. or link for the bracket you used?  The bracket you have would be much easier for inspection and replacement.  The original cutting board material shown (nylon?) only lasted about 500 miles but the UHMW seems to hold up well after 1500 miles. 

[ssevy]

I made my first block today, using a sawzall, a router, and a torch. I routed out a place for the bracket to inset for better stability, then countersunk a brass screw to hold it in place, and finally, melted it into place with a torch to curve the front angle and try to even up the surface a bit from where the router had been less than perfect.
My question for you is how did you smooth up the tube to mount the clamp? I have a broken bracket and a bead of welding to get off, and the grinder throws too many sparks for my comfort level. I tried a stone in my drill, but that just makes lots of fine stone dust. I do have some other tools to try, but perhaps you found an easy way to do this?
My other option is to take it to a welder friend and have him make a new mounting bracket for the new factory block I have, but without seeing the original in detail, it would just be a guess as to where to put it.
Here are some pictures:

[gcloys]

  Looks good!  I need that bracket, can you post a link? I've found some but just want to make sure I'm not missing something.  Just rechecked mine after 1200 miles and all is well.
  As for the broken bracket remnants I just used an angle grinder to smooth the surface.  It does throw sparks, but it shouldn't cause any problems.  You could shield the area with a wet towel if you're worried.  As long as your well-ventilated you probably won't explode!
  I have a bunch of pictures from my research showing where the original bracket was located.  From what I gleaned (from Mustang R.I.P.) the only (main) reason the rubbing block is there is to keep the chain from eating the frame mount.  I think our solutions are much better in the long run, and much more user friendly.  The original bracket is almost an afterthought in its design and is bound to snap off again.  Others have mounted urethane coated bearings or wheels etc like used on the DR650. 

[gcloys]

Here some pictures of the bracket mounting location

[ssevy]

https://www.amazon.com/dp/B0C893CB7C?psc=1&ref=ppx_yo2ov_dt_b_product_details

[gcloys]

Got 'em Thanks

[ssevy]

I used my Milwaukee 12 volt oscillating multi tool with a new blade to remove the weld and broken bracket, and it cut through it nice and evenly, leaving just a little smoothing to be done, easily accomplished with a cordless Dremel with a flapper wheel attachment.
It easily mounted by inserting from the back and spinning around into position. The bracket did require the thinnest spacer (the pair of brackets come with three thicknesses in the box).
I am going to take it for a long test ride today, and see how it works. If it is successful, I'll post up more photos and details to share.
Thanks for all of the info you have provided gcloys!

[gcloys]

Fantastic!  I rcvd my hinged brackets yesterday and will put them on at next oil change or when mine starts to rub through.  Glad you were able to cut it off without sparks flying! 

[ssevy]

Hold the presses!
The block worked great, but it needs some re-engineering from me. When I heated it to help it conform to the bracket, the hole that I drilled for the brass screw was thinned to the point that the screw popped through the block of plastic and the only thing holding it on was the front edge.
When I took it off, I discovered that you must remove it counterclockwise, as the curved part will not pass through the space with the sprocket cover installed. This means that the screw and nut are also too bulky to get through the space, even counterclockwise.
I am thinking about drilling and tapping the top strap of the bracket and using flatheaded countersunk screws to hold the plastic block in place, which could be mounted after inserting the bracket back around the frame tube so as to allow it to fit without removing the sprocket cover. Pop rivets might also do the job, but screws would make block replacement easier in the future.
I'm heading on vacation for a week, but when I return I will get it worked out and post up exactly what I did.

[gcloys]

Good information. Too bad it can't rotate through the space.  I think I remember that space measuring only about 1/2-3/4in (12.5-19mm).  Be nice to rotate for block inspection instead of removing the sprocket cover every time. I may need to invest in a cheap inspection camera for my phone or re-think the design.

[ssevy]

I re-engineered the block, and used some 1/4" thick material this time. The bracket does mount easily without removing anything but the rear shifter bolt (let it dangle). I'm going for a long test ride tomorrow, and if it works well, I will post up the pictures I took and the details of what I did. Fingers crossed that this works!

[gcloys]

I re-engineered the block, and used some 1/4" thick material this time. The bracket does mount easily without removing anything but the rear shifter bolt (let it dangle). I'm going for a long test ride tomorrow, and if it works well, I will post up the pictures I took and the details of what I did. Fingers crossed that this works!

Let us know how it went and post those pictures if possible. Sorry for the late reply, not getting or overlooking the notifications.
  Mine if still doing well after 2000 miles. I sourced my UHMW plastic from a 50 gallon plastic drum. I picked 2 up for free and use one for a rain barrel.  I'll have more plastic than I'll ever need!

[ssevy]

I purchased some 1/4" HPDE material used for boat decking, and it was quick work to cut it to the correct size. I drilled and tapped the aluminum clamp and used stainless screws to attach the HPDE, countersinking the holes and leaving enough thickness to keep the screws from tearing out.
Because of the size of the clamp, the long piece needs to be inserted from the front and spun into place, necessitating the attachment of the HPDE after the aluminum clamp has already been inserted.
I used blue Loctite on all three screws and aligned it by eye, centering the chain width-wise, and trying to keep the angle neutral from front to back.
I then did a test ride of about 275 miles, and while it initially made a loud buzzing sound as the chain wore down and created a groove in the plastic, it quieted down once the chain had established a bed in the HPDE.
It held up fine and would probably be serviceable as is, but the original factory block was curved and offered not only support to the chain, but also routed it closer to the upper rubbing block. With this flat block, my chain still seemed to have too much slack movement, so I modified the design and made up a second one using the other clamp I had on hand. Unfortunately, I can't road test this one until Spring, as the bike is now in storage for the winter.
Here are some photos to help clarify the written description:

The drilled block:


Tapping threads in the aluminum clamp. The locations are limited:


The drilled and tapped clamp:


Dry fitting before taking it apart for installation:


I did taper the leading edge to reduce the chance of tear out:


Installed on the bike:


Side view:


Sanding the new curved prototype:


Side profile:


Top view:


Side view attached to the clamp:


Once Spring returns, I will try this design and see if it provides additional chain support. One thing I did notice on the test ride was my mileage was about 36 mpg, versus the normal 40+ mpg, so I am wondering if the rubbing block friction was like having a brake hanging up, or hopefully it was just the low 40 degree F temperatures that day?

I will update once the new riding season opens up here in the Adirondacks.