Tutorial: Epoxy bonding of bushings in the CZ/Exo model stilts

[BitLord83]

Here is my tutorial for gluing bushings in the new CZ/Exo series bocks. I know this is pretty long, but I figured more details on what I learned the better.

The purpose of this mod is to have the pins slide in the bushings when the joint turns instead of the bushings sliding in the frame, making the bushings last much longer and keeping that annoying rattle from occurring.

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I recommend looking at the sticky-ed post of epoxy bonding of plastic bushes first before you read this as it has a video and is similar in concept as this tutorial, only it's for the old style stilts.
http://www.projumpforum.co.uk/index.php?topic=1271.0
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First, a list of things you will need to do this:

1) Two allen keys (hex) of the correct size.
2) 10mm wrench (if you want to remove the spring like I did)
3) Epoxy, the kind that you mix. Loctite and Gorilla Glue are good brands.
4) 150 grit and 300 grit sandpaper
5) Scissors
6) Acetone (probably best) or Isopropyl alcohol (rubbing alcohol)
7) Paper towels or some kind of clean rag
Toothpicks
9) Possibly a drill driver for polishing the pins.
10) Possibly pliers to remove the pins.


Some notes before you start:

I am by far an expert on this subject, but the following is what I did and what I learned while doing this project. Please feel free to correct me or add your knowledge. I will update this thread if I can with the long term results.

It's a pain but it will probably go better if you remove the spring first. This way you can just use the frame to clamp all the joints after you glue the bushings and let them all sit and cure all at once instead of waiting for each joint to dry before going to the next one.

The epoxy that I got takes 24 hours to dry at full strength. This is kind of annoying, but is a stronger epoxy than the quick set ones. I used some of the quick stuff and it didn't work so well in my old stilts. Also, the Gorilla Glue epoxy that I got said it was impact resistant.

Be patient! Rushing this job will probably make the project useless or fail early. Take your time and do it right the first time.

The pins and the bushings can be very stiff to get out sometimes. VERY carefully work out the pins. Use pliers if you need to but DO NOT use them directly on the pin itself, as you can put marks on the pin and make it wear the bushings out and not fit correctly inside the joint. Pad the pliers with some thick cloth or rubber. The bushings sometimes need to be pried out, but be VERY careful as you can crack them. It might be a good idea to get a few extras first.

You might want to get some thread lock (the stuff that you put on the screw threads that keeps them from coming undone) if you're worried about things getting loose. I personally didn't, but we will see how it works without it. I might be buying some soon, who knows.

Disclaimer: I am not responsible for your actions and what might happen to you or your stilts as a result of these instructions, etc.

So, here we go...

[BitLord83]

Let's start with the top joint (the one behind your knee that the top of the spring attaches to).

Every joint has the following parts:

1) Pin
2) Screw
3) Two washers
4) Two white bushings


With this particular joint, there is also a metal spacer that keeps the frame from bending inwards. It's fine if you glue this in place by accident as it doesn't matter whether it turns or not.

The bushings need to be glued into the frame itself for this joint.

[BitLord83]

Remove all the parts out of the joint by unscrewing it with your two allen keys.

*important* Make sure you prepare the surfaces you are going to be gluing well. Most of the time when glue fails, it's because the surface is either dirty, or too smooth.

Cut a strip of 150 grit sandpaper and use either an allen key or screw driver and move it back and forth through the holes in the frame where the bushings go. The idea is the scratch it in the opposite direction as the forces want to turn the bushings. See picture.

Don't wear down the holes or smooth them out, just make sure they are scratched up a bit. Take your 150 grit and do the same on the outside of the frame where the bushing face sits. See pictures.

[BitLord83]

Now lets prepare the bushings.

Take your 150 grit sandpaper and you want to scratch up the bushings a bit. Be careful as the bushings are softer than the frame. Remember, you just want to make them slightly rough. Don't wear them down any.

Again, sand in the opposite direction that the bushing will want to turn. Do this all the way around. See pictures.

[BitLord83]

Now we need to make sure the pins slide easily inside the bushings.

For me, all but one joint was smooth and needed no further modification. In one joint however, the bushings were very tight on the pin, and the bushings were quite tight in the frame.

Be very careful when removing the pin and bushings. You don't want to break or bend anything, or put any dents in the pin. Be patient!

Carefully use your 150 grit sandpaper to sand down the pin by wrapping the sandpaper around the pin and turning the pin back and forth. Do not sand lengthwise. Sorry, didn't get any pictures of this part.

Once you've sanded the pin enough to the point where the bushings can slide easily on it, then do the same thing with the 300 grit sand paper until the pin is nice and smooth again. Now the bushings should slide easily just like they will when you're using your stilts.

I've heard that it might make the job easier to carefully clamp the pin in a drill driver and spin it while you are using the sand paper on it. I personally didn't need to do this with my stilts. I would do it by hand if you can since there is more control. It didn't take me very long to sand it down by hand any way.

[BitLord83]

Almost to the gluing!

First it's very important that we thoroughly clean everything that is to be glued. Use your Acetone or alcohol on a paper towel or clean cloth and wipe down your bushings (the parts that contact the stilt frame). Do the same for the holes in the frame where the bushings sit.

Make sure everything is nice and dry before you glue anything!

Make sure you get all your glue stuff ready: toothpicks, something to mix the epoxy with, several pieces of paper towel for cleanup.

Notes on epoxy:
1) Make sure you use even amounts of both the glue and the hardener.
2) Make sure you mix it very well.
3) Use it rather quickly. The quicker the better.

I found it best to mix a small amount, just enough for one joint, and then wipe up the rest when done. Then I would just mix a fresh batch for each joint.

Now take your newly mixed epoxy glue and use a toothpick to coat the inside of the holes in your frame. Next, use the toothpick to put a bead of glue around the bushings. Remember, the glue only goes on the parts that will be in contact with the frame.

*Please see the sticky-ed tutorial on epoxy bonding of plastic bushes for the old style stilts if you need more visuals on where to put glue on the bushings.*

When you put the bushings in you will need to line up the metal spacer first so that the bushings and the spacer all fit together correctly just like they were before we took the joint apart.

When you push the bushings in, you might get some epoxy glue that pushes out of the edges. Just use a paper towel and clean up any excess. We don't want the joint all glued together.

Carefully put the bracket back over the joint and put your pin through the bushings (don't forget the washers). Screw in the screw nice and tight just as if you were putting your stilts back together. See picture.

**Do not move the joint until the full drying period is over!**

[BitLord83]

Now we can move onto the other two joints.

Both the joint right under the footplate and the joint that attaches to the spring are built the same, just one is wider than the other. See pictures.

I would glue the joint that attaches to the spring first since that one is not likely to be moved as easily, letting it set properly while you work on the joint under footplate.

[BitLord83]

Gluing the bushings in the support bar is very similar to gluing the ones in the frame.

Take your screwdriver or allen key and a strip of 150 grit sandpaper and rough up the insides where the bushings sit. Make sure sure you sand in and out. Remember, we're just trying to make it a little rough, not smooth out or sand it down. See picture.

Also sand the outside lip (where the bushing rim sits). Again, just give it some scratches so the glue will stick well. See picture.

[BitLord83]

Next sand the bushings as I previously explained.

Clean the bushings as previously and everything where the bushings will sit in the support bar. Make sure it's fully dry before gluing

Prepare your epoxy glue as previously explained.

Use a toothpick to put a coating of glue inside where the bushings is going to go. Don't put the glue all the way in, just in the place where the bushing is going to sit.

Put glue on the bushings as previously explained.

Put your bushings in place. Make sure you wipe off any extra glue!

When I did mine, I took a look through the bushings once they were in place and noticed a blob of glue on the inside of the joint since I had put a little too much in. I took one of the allen keys and wrapped a paper towel around it and slid it through the joint. I kept doing this until there was as little excess glue in the joint as possible. Make sure you hold the bushings in place when you do this to keep them from moving.

Now assemble the joint as previously explained. Do this for the joint that attaches to the spring first, then for the joint right under the footplate. Make sure not to move the first joint when you are doing the second one. I also put the support bar as far up under the footplate as possible, making it less likely to be hit while it was drying. See pictures.

Now let them sit for the FULL drying period.

[BitLord83]

And finally...

Once your stilts are fully dry (in my case, 24 hours) very carefully undo each joint one at a time.

I found that the two lower joints had a little glue in them, but broke loose pretty easily. The pins didn't come out very easily on a couple of them.

I carefully worked the pins out and found a little glue on some of them. I was able to sand or scr***e off any glue (make sure you use the 300 grit last so the pin is smooth). You might also want to use your allen key or screwdriver to run a strip of sand paper through the joint and get any excess pieces of glue out. Look through it afterwards to make sure.

Also, if the pins aren't turning quite so smoothly in the joint any more you might need to sand the pins down a little more until they're good. Remember to smooth them with the 300 grit sandpaper.

I found once I got out any excess dried glue each joint worked smoothly.

Also, a pin might turn more smoothly when put in the left or right side of the joint. Put in the pin whichever way is best.

You might also want to put some lubricant (silicone is probably best) on the pins before putting them through the joints.

Do up all the joints nice and tight (not too tight) and put the springs back on.

Nice job. Give yourself a pat on the back!

[Jason]

Nice tutorial BitLord

And some good pics to make it easy to understand

A couple of things I do when assembling the joints

I put silicon grease on the pins as I assemble them as this stops the glue sticking to the pins

If you polish the pins up in a drill I would suggest 1000/1200 grade wet and dry (or even finer) as this will polish them rather than sanding them

The shinier the pins are the longer the bushes will last (I give them a last touch with solvo autosol polish to make a mirror finish)

Nice to see such a well writen run through mate

Well done

Jason 

[BitLord83]

Thanks. I'm glad I did ok.