[SEL] Trailer Brakes - Question

[Listerdiesel]

We've got the trailer building hat on, and are looking at a new
trailer, partly to carry the Ruston 1ZHR and also to provide a
comfortable living area for us while we are at rallies/shows. In the
UK, most folks go camping if they cannot bring a caravan along, as
local hotels etc are pretty expensive.

The overall length of the body is just over 6.6 metres or just over 21
feet. It will have three axles in a drawbar/front steering axle
configuration, maximum weight is 3.5 tons all-up. We are allowed 7
metres for the class of towing vehicle that we have.

So, we are limited to overrun braking (surge brakes) and probably
mechanical. The front steering axle rotates on its centre pivot, the
two axles at the back are in tandem and fixed to the chassis.

To provide equalised braking, we have to fit two compensators, one
between the front axle and the rear two axles, mechanically weighted
to allow double the braking effort to go to the rear axles, and then
another equaliser/compensator between the rear axles.

To get an idea of the layout, see this image:

http://www.stationary-engine.net/Forum/Images/Uploaded/Drawbar1Iss3.jpg

What we are thinking about is the type of braking linkage:

1) Do we go for full hydraulic?  Possible but nothing is type-approved.
2) Cables?  Easier but they take a lot of maintenance unless you get
the newer stainless types.
3) Rods and swivels?  Less maintenance and friction, don't know if the
parts are still made.

Electric brakes are not approved in the EC, we have already looked
into that one.

With new-build trailers likely to need annual testing soon, we want to
make sure that what we build isn't going to be a PITA to look after or
get through its annual test, as and when that happens.

The front axle pivots on a 75mm vertical steel bar which runs in two
large flanged self-aligning bearings, with a thrust ball race taking
the vertical loading.

Any thought would be appreciated.  Half a ton of box section is at the
machine shop waiting for a few clear days.... The main body is going
to be standard truck body extrusions in ali, with honeycomb sandwich
side panelling.

Peter
-- 
Peter A Forbes
Email: listerdiesel at gmail.com
http://www.oldengine.org/members/diesel
http://stationary-engine.co.uk
http://www.oldengine.co.uk