Introduction: Repairing a Softride Rocket Beam
[Note that there is now an improved version of these instructions in the Facebook Softrides group: https://www.facebook.com/groups/36519069043/permalink/10159276818359044/]
Softride Rocket/Fastt bikes have a common fault: the elastomer (inside the metal sleeve) 'slips' on the carbon beam.
If your Softride Rocket/Fastt beam has slipped, you have no choice but to fix it yourself, because Softride has stopped making bikes, and new beams are no longer available.
Here's how to fix a slipped Rocket Beam.
[Note that these instructions only apply to Softride's "Rocket" beam (straight carbon beam with a metal sleeve), not to the "Classic" beam (curved carbon beam with a foam sandwich)]
Step 1: Extracting the Sleeve
The first thing you need to do is press the sleeve off the beam.
This is too hard to do by hand, so we need to make a jig that forces off the sleeve without damaging the beam. Whatever method you use, the sleeve won't slide off quickly. It's a slow process as the two parts still have a lot of friction together
The simplest jig is a trailer hitch jack and some strong cable. To make this jig:
1. remove the beam pivot bushings from the bike, and place them in the beam pivot
2. tie a piece of strong steel wire(e.g. a clothes hanger) around the beam pivot bushings, and down to the jack's base
3. tie another piece of strong wire underneath the 'tongue' of the sleeve, to the top to the jack
4. extend the jack to pull the sleeve off, holding the end of the beam to keep it vertical.
A more sophisticated jig uses two threaded rods to force the sleeve off the beam. To make our jig, we need:
- Some 'L' shaped angle iron at least 50mm wide and 3-5mm thickness
- 16mm drill bit
- two threaded studding rods about 14mm diamater and as long as your beam (we won't damage these, so you can borrow them off someone)
- 6 bolts and two washers to fit your studding.
- a block of wood at least 200mm long
- a 'G' clamp
First we have to make the 'L' backets that connect our jig to the beam's upper pivot.
1. Cut two 30mm strips off your 'L' shaped angle iron.
2. Drill a hole on each face of your angle iron, 25mm from the corner, and go up your drill sizes until you reach a 16mm diamater hole
3. Take the upper pivot bolts out of the end of your Softride beam, and bolt the L backets on.
Next we need to make the wooden black that will press against the sleeve
1. Take your large block of wood and mark the location of the holes you will need to drill, by placing it against your L brackets you just assembled and tracing the holes with a pen.
2. Drill the holes out to 16mm, (or whatever width your studding is) so the studding fits through
Now we need to assemble and use the jig.
1. spin three nuts onto each piece of studding. Splin them down as far as your wooden block is thick. Tighten the top two nuts against each other to lock them in place, and put a washer on top of them
2. push your two studding rods into the holes on your wooden block. Put the other ends of the studding through the holes in your L brackets
3. move the block against the 'tongue' of your beam's sleeve, and spin the thrid nut (the one that isn't locked) until it reaches the L bracket
4. Keep turning the third nuts until the wooden block presses hard against the 'tongue' of your beam's sleeve. Turning the nuts like this will eventually press the sleeve off your beam
5. Take your G clamp and clamp the outside endges of the L brackets (like in the phtoto), so they don't splay outwards under load and damage your pivot.
Step 2: Extracting the Elastomer
We need to get rid of the old elastomer, so we can cast new elastomer.
Things you will need for this step:
- Polymorph (heat moldable nylon)
- large tray or bucket
- putty knife or sharp flat screwdriver
- dishwashing gloves
- 80 grit sandpaper
Before removing the elastomer, we need to make a jig of how the sleeve fits on the beam, so we can cast it back into the correct location.
1. push the beam gently back into one end of the sleeve just enough that it fits snugly
2. boil water and put half the Ploymorph into it until it melts
3. mold the Polymorph around the junction between beam and sleeve, making sure the whole junction is covered.
4. wait a few minutes for the Polymorph to harden, then remove the beam and insert it into the other end of the sleeve
5. put the other half of the Polymorph into the boilding water and mould the other end of the sleeve. You now have a pair of cups that will hold the beam in place in the middle of the sleeve, when we pour new elastomer in later.
6. mark exactly where the cups are by taping a strip of masking tape around the beam at the edge of one cup, then trace its edge with a pen, to mark its position.
7. take the smaller cup that is closest to the beam pivot, and cut a 10mm wide hole in it s edge. We will use this hole to pour in the new elastomer later.
Now we need to remove the old elastomer from the sleeve. It is best to heat up the elastomer to loosen its atachment to the sleeve (heating makes a huge difference).
1. Boil a few litres of water. If you have a large flat metal tray that you can boil water in on your stove top, that works best. Otherwise take a bucket that is big enough for the sleeve to lie flat in, and boil the water in your kettle.
2. Put on your dishwashing gloves - we're going to play with boiling water and don't want to burn our hands
3. Immerse the sleeve in boiling water for a minute, to make the elastomer soft. The water needs to be very close to boiling for it to be effective.
4. Using a putty knife or sharp screwdriver, scrape out the elastomer. It should detach from the sleeve if you push firmly.
5. Return the sleeve to the boiling water every 30 seconds or so, to keep the elastomer soft.
6. When you have finished pulling the elastomer off, there will still be some small bits of elastomer remaining. Use the 80 grit sandpaper to grind these away. (A faster way is to use a flap-wheel drill bit. You'll need a small-diameter one with a long shank to get all the way inside the sleeve.)
7. Keep on sanding until all the old elastomer is gone. Don't worry about scraping up the inside of the sleeve - those scrape marks will help the new elastomer to bond well, and they won't be visible.
Step 3: Creating the Serrated Surface
Because we don't want the beam to fail again, we're going to create a better surface on the carbon beam for the elastomer to bond to. During my testing, beams that didn't have this improved surface failed again very quickly.
You will need:
- Araldide epoxy
- 50 rubber bands (2mm width, 50mm diameter) or chop up an old mountain bike inner tube
- 100 grit sandpaper
Get rid of the shiny surface finish
[If your beam is from 2005 or later, you can skip this step because your beam is already roughened]
1. use masking tape to trace around the area where the sleeve normally sits. Take an extra 5mm, to prevent accidentally sanding too far onto the visible finish.
2. using the 100 grit sandpaper, sand back the shiny coating until it appears dull
3. clean the surface with a degreaser
Create the serrated finish
1. using masking tape, mask off the area to outside where the sleeve normally sits. Move the tape inwards an extra 5mm, to leave a generous amount of space to the edge of the sleeve, because you don't want the ridges to be visible
2. make sure to fit the polymorph end holder for your beam sleeve - because you won't be able to put it on after you have made the ridges!
3. place all the rubber bands around the beam, beginning at the pivot. Leave one band's space between each band to create the spaces between the ridges, so there are stripes of rubber band. A chopped-up old mountain bike inner-tube makes the perfect size bands, so get one and slice it into 4mm wide strips.
4. put another layer of masking tape on top of the rubber bands to mask off the extent of the ridges. This will prevent epoxy getting everywhere
5. mix high-strength epoxy. I've used Araldite 2000. Apply it evenly to the spaces between the rubber bands. Make sure you don't glue past the masking tape. Wipe off any excess that is taller than the rubber bands. Leave it for 3 hours to half-set, angling the beam pivot-up so the epoxy won't drip into the sleeve and glue it in place!
6. when the Araldite has partially set, we need to remove the rubber bands. After 40 minutes, test the glue by peeling off the top layer of masking tape and cutting one of the rubber bands. Try to time it just right - if the glue is too soft, removing the rubber band will leave gooey trails of glue as it is removed, and the edges of glue either side will slump and become very rounded. If the glue is too hard, the strip of glue will be pulled off with the rubber band.
You now have a serrated finish
Step 4: Pouring the Polyurethane Elastomer
We need to pour new elastomer, to bond the sleeve onto the beam.
The guy who specified the original urethane for Softride has said on the Facebook Softride thread (https://www.facebook.com/groups/36519069043/):
I used to work for Softride and helped them with the urethane spec for rocket beam delams. The urethane they were using was a 20 shore A and had poor tear strength and the aluminum sleeve was not properly prepped for the adhesive properties necessary for a good bond. A 40 shore A urethane will still allow the beam to shear and offer the comfortable ride you desire. You need to prep the aluminum sleeve with a special primer that needs to be post cured as well.....
...I am a little biased but know that a 40 shore A that is sold by PTM&W industries product PT7240A/B will work great. Full disclosure, I am a tech rep for PTM&W and helped softride find the right product. The material is available in quart kits and than be ordered by calling 562-946-4511. Make sure to keep moisture away from all liquid urethane systems as it causes them to foam up. I am referring to when you open the can. Once cured they are fine but have been known to absorb moisture over time once cured.
You will need:
- 500ml "Shore 40" grade polyurethane elastomer (the PTM&W polyurethane is http://www.ptm-w.com/index.asp?pgid=24 I have used http://www.mouldlife.co.uk/?pageid=subcatshow&fam...)
- a well-ventilated area
- latex gloves
- safety glasses
- a disposable stirring pot and stirrer
- an A3 size piece of flexible cardboard
- disposable kitchen wipes
- acetone based de-greaser
- a small dish of water
- masking tape
- a big carboard box to do the messy pouring in (you're going to spill elastomer all over the place, it can't be helped)
Set up the sleeve
1. using tape, mask off the area that the old elastomer lived, carefully making sure the edge is smooth.
2. wipe down the beam surface you want to bond to using acetone or degreaser, and wait 10 minutes for it to dry off
3. place the polymorph jigs over the ends of the beam in the exact position and slide the sleeve onto the beam. Be very careful to get the position right, because a few mm shift in beam position makes a big difference in seat height.
5. put on your gloves and thoroughly mix the polyurethane in a disposable pot, equal parts by weight of each part. Use scales because the different parts have different densities. Be careful not to touch or breathe it in because this stuff is poisonous
6. make a funnel for pouring into the gap you made in the sleeve, using the cardboard, by curving it into the sleeve
7. lift up the rear polymorph cover and pour the mixed polyurethane through the funnel into the sleeve, making sure you fill slightly past the top. Angle your beam so the trailing edge is horizontal, so it will fill up evenly.
8. Afte a few minutes, come back and top up the elastomer to the top of the sleeve. Don't worry if there are drips everywhere, it's pretty easy to buff off when it's dry.
9. after half an hour, if you have messy edges (and you probably will) dip your (gloved) fingers into some water (so they are wet, but not dripping) and wipe off any excess, smoothing down the edges
After a few day's curing, (faster somewhere warm like in your hot water closet) your beam is ready! (a sweet, sweet sight)
- aluminium primer is still being investigated