Sunday, 12 June 2011

Front Brake Repairs

The Brox uses many non-standard and (now) obsolete parts. If such a thing as a repair manual for the machine exists I'd be very grateful for a copy. Meantime I'll post any information I find.

The front brakes are a pair of Sachs power discs, these are now obsolete and owners of machines originally built with them like the older Greenspeed GTT, AnthroTech and the Brox Compact all face the problem of servicing them and finding suitable replacements. I have found the old parts list on-line, the brake is on page 59 and the service kit on page 135 - this dates back to 1999.

The newer versions of the Greenspeed and AnthroTech both now use the Mangura Big Twin (more info), however the mounting arrangements are different. Pedicab shop advertise them for sale in the UK.

The following is the story of the conversion of the Firebrox to the Mangura brakes. It is reposted from FireBrox Repairs - in case the original ever disappears.

This front brake replacement is one repair I am not looking foward to - I hope I can find a simpler alternative!

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Just about all the bearing surfaces have been changed, wheels, headsets (all 3 of them), gear cassette rebuilt, new custom chainguard fitted, chains replaced (both of them), repainted sound chassis, perspex panels cut and replaced, an overhaul, rewire and simplification of the sound system, speaker array mounts replaced, binding brakes fixed. I'm sure there are some things I've forgotten we've done.

This has been a time consuming task as the Brox is very nonstandard. Bearing surfaces were very hard to source and eventually had to be machined to fit. Every time we work on it we hit an unforseen wall of some description or another. Work has also been delayed by my being out of the country for 3 weeks as I have been made redundant recently, but had the offer of work teaching freediving in Dahab, got to get the work no matter how unpleasant ;)

So all in all sorry it's taking so long, I want it out of my garage and back on the road too, but we have one major problem which is a show stopper, the brakes, these have to be bled (no, it's not at all like a car), but as a result of the calipers being obsolete, we cannot get the spares or the correct bleeding kit to get all the air out of the system. WOTNOBRAKES?!?!? Yes indeed, no flippin' brakes, so you can see, this has to be resolved before we can possibly use it on the road.

We are close boys and girls and no one is missing the Brox like me, as I have some truely killer mixes stacking up at home ready to play on the LFNS.

So watch this space, once the brakes are working safely we can reassemble the poor beast and bring it out again as a more reliable deliverer of music.



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The problem: The new disc brake calliper uses a completely different mounting arrangement to the old one, and because the old system is obsolete there's no standard adaptor available so a pair has to specially made. The other problem is that with this particular combination of hub, disc and calliper the spokes hit the outside of the calliper so a 5mm thick spacer is needed between the disc and hub to position the disc and calliper further away from the wheel. This in turn means that the disc is now too close to the frame and the heads of the disc fixing bolts hit it, so a longer spacer is needed on the axle to move the entire wheel assembly outwards. However this puts more stress on the axle bolt as it is cantilevered out from the frame. Although it's only a couple of millimetres any increase in stress is not good as the Firebrox is heavily loaded and inclined to go through potholes. The solution is to make the new axle spacer cone shaped so that the face that sits against the frame is a larger diameter than the original thus reducing the leverage and the tension on the axle bolt.



The raw materials: A couple of conveniently shaped lumps of aluminium and a length of steel bar from scrap metal the collection.



After playing with most of my favourite engineering toys we end up with these. Hope it all works...




All photos are by the Firbrox crew.

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