Thanks to those who replied before. I now have some pictures of the trailer braking system in question.
The brake drum is approximately 190mm across.
What do you think my options are? Are parts still available? Is this system autoreverse? Notice the little lever on the coupling. Is this a manual reverse selector?
Christian.
No, this is not an auto reverse unit, you see the clip/lever at the rear? this has to be pushed rear wards, when the vehicles are sitting stationery, you push it rear wards, and it releases the over run shaft so it can travel all the way back, if the lever is not actuated the trailer brakes will just come on preventing you from reversing at all. It will be necessary to have someone with you when you want to reverse, to actuate the lever as getting in and out of the car to do it yourself may become tiresome, especially if you need to make several attempts to position the caravan. as far as parts being still available goes I think it'll be a matter of opening up the hubs and taking a serial No. and checking availability at a caravan accessory shop, or trailer parts specialist, if you cant find the numbers in the shop, you may need to take the parts with you. hope this helps you in your quest!! regards.
Sorry I didn't look at previous thread.
Looks like an old indespension part to me.
Pass
No
Yes
AJH
It looks like an Indespension unit
If not it's easy enough to replace them with more modern bits.
To me, it looks like:
Anyone like to comment? Is this the BMC system referred to elsewhere?
Christian.
I'm not just someone Peter, I'm the proud user of a pre owned Alfa, gifted me by a denizen of this group ;-), 1000 more miles under its belt after taking me on excursions to Scafell pike and the Brecon Horseshoe, well nearly all the way.
AJH
There's more. In order to get the brakes working, I need to get some idea if I can fix the coupling. Obviously there is no point fixing the brakes without a working non-autoreverse coupling, unless you can still buy manual couplings (I've seen those old spring ones, but this isn't one of those).
The coupling is a Bradley HU2B, apparently (650-1000kg). I've take the hitch off the front and am left with 2 concentric tubes. The internal one seems to be connected to some sort of shock absorber. It slowly pushes forwards, but can be pushed back down its tube. The outer tube appears to be locked solidly in its housing. I presume that this tube is also supposed to move. Otherwise, the internal tube is also locked in place.
How am I supposed to free this tube?
Christian.
You know, looking at some brake part catalogues, the shoes look pretty similar to the current Knott parts. I wonder if I have non-autoreverse Knott parts?
Does anyone agree?
Christian.
It does look very similar!
I'm pretty sure that what you've got *isn't* a Mini hub - for 2 reasons. Firstly, you appear to have an integral hub and brake drum. As far as I can remember, the Mini had separate components - so that you could remove the brake drum, leaving the hub and bearings in place. Secondly, the mini had hydraulic rear brakes, plus a mechanical means of speading the shoes when the handbrake was applied. Your photo shows no hint of a hydraulic slave cylinder - or of a gap left by removing one.
If it *is* a BMC hub, it would have to be off something of A35 vintage (1950's) which had a hybrid system in which the front brakes were pure hydraulic but the rear brakes had an hydraulic slave cylinder under the floor which operated on the handbrake linkage, so that there were no hydraulics actually inside the rear brake drums.
I would say that your hubs were specifically designed for a trailer rather than being adapted car units. They may *even* be auto-reversing, even though the catch on the hitch suggests otherwise. It seems to me from your photo of the backplate with the drum removed that there are more moving parts and springs than would be required for non-auto-reversing brakes.
Yes. I'm sort of hoping that these are autoreversing due to some previous partial replacement, so I just need new shoes and an autoreverse hitch, especially given that the previous hitch is pretty shagged. I'm going to empty a can of WD40 down the (only) grease nipple to try and free the tube. The manual reverse lever doesn't even fit in the appropriate slot. I have severe doubts as to fixing the coupling at all, let alone getting it to reverse.
If I do manage to free the coupling, can I convert it to autoreverse by simply adding an energy store?
BTW, do you know how the Knott brakes are measured? I made it 190mm across the drum, but not very accurately and forgot to measure it properly when it was off the backplate. New knott brake systems seem to be 160mm or 203mm, which aren't even close. Do you know where the measurement is taken, so I can see if I have one or the other of these?
Christian.
Possibly, if you can get a bolt-on one, and if the handbrake lever has enough travel to compress the energy store in addition to applying the brakes.
I've just had a grovel under my (1991) caravan to remind myself how the brake linkage works. Immediately behind the plunging hitch there is a vertical lever, pivoted below hitch level. The plunging hitch pushes the top of this lever backwards. The brake rod is attached to the bottom of this lever, below the pivot - but quite close to the pivot in order to provide a force multiplication of 3 or 4 to one. The handbrake lever pivots on the same axis as this first lever, but to one side. There is an arm on the bottom of the handbrake lever which pulls on the back of the energy store. The energy store is a cylinder surrounding and concentric with the brake rod, with a spring of some sort inside. [I can't see whether it's metal or rubber].
The reason for describing all this is that it is obviously designed as a unit, and I suspect that you may be better off installing a complete unit - particularly if you can't easily unseize your hitch.
A fiew thoughts Christian.
If the trailer was rated at 750-1000kg I'm not sure Mini hubs / tyres would take the load?
I pretty sure Car Springs (later incorperated into Enfield Leisure) didn't stock / supply / use Indespension units but a cheaper (more basic) variety?
They used to supply units rated to 10 cwt (load) that would take Morris Minor running gear (as mentioned before) or complete units in both braked and unbraked form. I think it had a hole in each drum that you could adjust the shoes through (I can't remember seeing such on your photos so it may have been a production unit).
My trailer is cable braked using an un-damped overrun coupling where the reverse locking mech is simply a flap that flips over between the hitch and the body and stops it sliding back. Better than the auto releasing type you may have as you only need to set it once, but you do also need to unset it .. ;-)
I bet with a good wire brushing, a coat of paint and a re-grease it will all look lovely in there (memories of building our kit-car)
All the best ..
T i m
They are definitely closer to the Knott brakes than anything else I've seen. Right down to having a bolt arrangement for brake adjustment, rather than window and gear wheel.
I think mine might be more recent. It is definitely a hydraulic overrun, rather than undamped spring one.
Yes, as long as you're not talking about the brakes linings there! ;-)
P.S. Was thinking of replacing the plywood floor with a sheet of steel/aluminium. Can you think of a reason not to?
| P.S. Was thinking of replacing the plywood floor with a sheet of | steel/aluminium. Can you think of a reason not to?
I replaced mine with exterior grade ply, and varnished it, lasted a lot of years and still going.
Dave F
Erm .. welll, assuming you can't find a direct replacement you could get yours relined? In the 'good old days' I was known to re-rivet shoes on some of my cars .. in fact from memory I think my Messerschmitt has that system?
Yes, it's not very 'stiff' / absorbant / light as marine ply. You could put a skin of metal over the top if you were only hauling rubble but stuff will slide all over the place?
I built my 6' 6" x 4' x 3' high 1/2 ton 'box' trailer for use with a mobile disco. I sold it to a mate for a few years then bought it back and converted it to a 'good's' trailer. I actually used the old marine ply side panels and front / tailgate cut down to 18" and they were probably 15 years old at the time (and the trailer was kept outside). I think I replaced the floor though.
All the best ..
T i m
My local Indespension reckon that they might be the older pre 1989 160mm Knott brakes. The good news is that new shoes are available. The bad news is that they want 57+VAT per brake, making it over 130 quid just for a set of shoes. The better news is that a company called Saftek will apparently shotblast and reline the existing shoes for 6.25 each. So with a nice wirewooling of the rest of the components and a new expander I might be able to get these old things going again.
God knows if can free the old coupling, though. It's over a 100 quid for a new one.
Christian.
It would almost be cheaper to buy a new trailer, wouldn't it?
.andy
To email, substitute .nospam with .gl
A braked 8x4 trailer would be well over 1000 quid. Some makes might even approach twice that.
I think that 26 quid on shoes and 20 quid on expanders to get the brakes themselves working is pretty good value!
Even if the new coupling is needed to get the overrun working, it is still a fraction of the price that you would expect to pay, even taking into account the purchase price (on eBay).
Christian.
OK. Didn't realise it was as large as that or that they were as expensive..
yes indeed.
.andy
To email, substitute .nospam with .gl
Yes. There's quite a step change when brakes are involved. I've even seen an unbraked single axle 8x4 go for around 900 quid new. A braked single axle Ifor Williams version seems to be around the 1400 mark, although the example I saw had a higher gross weight (1250kg). This was going out on eBay at around the 900 quid mark, snipe bidding discounted.
Christian.
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