Chair Problems

A couple of posts ago I said I had a problem with the R80/2 sidecar outfit and I decided to get this sorted out before I started on the R12.

The problem I had was with the sidecar’s mudguard (fender).

On a Steib this is a big, Art Deco affair. Originally it would have been a pair of steel pressings spot-welded together but this was replaced with a fibre-glass (GRP if you prefer the term) replica about 40 years ago.

At the rear of the guard a chassis tube goes through it from side to side and the guard is held in place between a pair of conical mounts (there is a reinforcing cross tube goes here, between the two sides of the guard).

What has happened was that over the years the fibre-glass guard had gradually worn at the conical mounts until the inboard one pulled through. The guard then could move/bounce on the cross tube and by the time I got back home, I was some 150 miles from home when it went, the hole in the guard was not only oversize but oval. On further examination I found that the outboard mount was also “somewhat under par!.

Normally a repair on a fibre item is a simple matter, just clag on a bit more mat and resin! but here I needed to reform the seats for the conical mounts so I needed a former.

As I only needed to make up two mounts I just made up a temporary former using MDF board.

The maximum diameter of the conical mount was 50mm so I cut a round of inch thick MDF that size. The diameter of the cross tube is 32mm but as there needs to be a clearance on that I worked with 35mm as the minimum and I carved it down to a cone of those dimensions and 15mm high so I had a 35mm cylinder an inch high with a 15mm high conical base.

Next step was to make up a female piece to match this, as there was only space on the inside of the guard to take a 100mm square block this determined the outer dimension of the female mould.

When you are working with fibre-glass you normally have only a short “time window” to work in before the resin starts to gel and owing to the nature of my intended repair this was a problem.

However there is an alternative resin available, “Epoxy Resin” rather than the more usual “Polyester Resin” and this has a longer pot life, of around 6 hours plus rather than only 15 minutes and so I opted to use this.

Rather than just try to patch the guard I used the mould to make up a light support moulding for the main repair.

I took a 150mm square of MDF and drilled an 8mm hole in the centre, there was already a similar hole in the round male block so I fixed them together with a length of 8mm studding (allthread) and gave the resulting plug a good coating of mould parting compound, and I similarly dosed the female block.

Then I laid up the mould, using a layer of fine glass cloth and a single layer of chopped strand mat. I then put the female part over the centre piece and used the studding to force it against the lower part and left it overnight to cure.

When I extracted the “casting” from the mould I had what was to become the outer surface of the repair just needing trimming to size.

I then re-assembled the casting onto the mould plug, but this time sandwiched a sheet of polythene between them, the resin will not stick to this and it meant it would be easier to remove the plug.

A single layer of the chopped mat was now laid up onto the back of the casting and another onto the guard itself, being generous with the resin, the moulding put onto the prepared guard and the whole turned over to let me work on the inside of the guard.

The casting was adjusted for position to correct for the wear to the guard and the wear gap made good with mat and resin and then another two layers of mat and resin laid up on the inside of the guard.

I’d bored some 10mm holes through the guard so that the resin would bond through them to combine both sides of the repair together.

Once I had the inside laid up I put a sheet of polythene over it, put the female part of the mould over the plug and again squeezed the wet resin/glass layers together and again left it overnight.

Next day I removed the mould, a fairly easy job thanks to the polythene.

I then had to set to and repeat the whole process for the other side of the guard but once that was done all that was left to do was clean up the surface, fill the blebs with bondo, rub it down and get out the rattle cans to repaint.

It’s not a perfect job but you have to look to see it and as a new guard is around 250 quid plus carriage from Germany I’m willing to live with it for use on the road hack.

If I’d been willing to cut back with a sander on the outside of the guard after the repair it could probably have made to look as original but this is the main mount point for the guard and I’d rather a bit of strength over cosmetic perfection.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.