Trailer brake

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tanvics71
Posts: 3
Joined: Tue Apr 03, 2018 7:53 am

Trailer brake

Post by tanvics71 » Fri Mar 15, 2019 8:13 pm

I’m looking to add trailer braking to one of my Marshall’s as I have purchased a lowloader anyone know where I can get a dot 4 compatible trailer brake valve new or used ,
Or has anyone rigged to spool valve (my dad used to when I was young) but managed to dropbflow rate /pressure so they not so sharpe

Pete



DAL PZ
Posts: 57
Joined: Mon Apr 09, 2018 10:39 am

Re: Trailer brake

Post by DAL PZ » Fri Mar 15, 2019 11:14 pm

Rick Cobley is your man for this I believe he has made up a system to do this

diggerdeano
Senior Member
Posts: 339
Joined: Sat Mar 31, 2018 9:04 am
Great Britain

Re: Trailer brake

Post by diggerdeano » Sat Mar 16, 2019 8:49 am

ford and DB used the same set up but they use mineral brake fluid so they would require resealing with the right seals

Rick Cobley
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Great Britain

Re: Trailer brake

Post by Rick Cobley » Sat Mar 16, 2019 9:12 am

diggerdeano wrote:
Sat Mar 16, 2019 8:49 am
ford and DB used the same set up but they use mineral brake fluid so they would require resealing with the right seals
What type of brake fluid is used in Marshall tractors?

Rick Cobley
Posts: 210
Joined: Fri Mar 30, 2018 9:32 pm
Contact:
Great Britain

Re: Trailer brake

Post by Rick Cobley » Sat Mar 16, 2019 9:13 am

A trailer brake valve off a Massey found its way onto my Leyland 285!

tanvics71
Posts: 3
Joined: Tue Apr 03, 2018 7:53 am

Re: Trailer brake

Post by tanvics71 » Sat Mar 16, 2019 2:30 pm

Marshall’s are dot 4 same as Leyland I can get one off a international but they use mineral old so no good a not sure if and where to get new seals for dot 4

APH463
Posts: 4
Joined: Sun Apr 01, 2018 5:07 pm
Great Britain

Re: Trailer brake

Post by APH463 » Sat Mar 16, 2019 3:24 pm

we used to run trailer brakes off the spool valve , you need the male fitting into the spool valve and female fitting for the trailer brake connection and if you can't reduce the pressure from the tractor end what you can do is to use a plate something like the little round plates that you knock out of a 240 volt electric box to get the wires in , and drill a small hole in the centre of the plate, about 2/3mm and put it inside the 2 fittings(in between) , this will work . Disc markers on a accord drill use the same system , all you are doing is reducing the oil flow to stop the ram seals blowing out. You may have to experiment with the size of the hole in the centre of the disc. We had at the time about 6 tractors on trailer work that had to use this . What I'm saying is that it has been done like this in the past but today is a ?. Phil

NormalforNorfolk
Posts: 10
Joined: Fri Mar 30, 2018 10:31 pm
Great Britain

Re: Trailer brake

Post by NormalforNorfolk » Wed Mar 27, 2019 10:10 pm

One word .... (well 3 really) ..... Don't Do It!!

A trailer brake ram needs to be controlled by PRESSURE variation, NOT flow. If you put a restrictor in the hydraulic line, all you are doing is reducing the flow rate and thereby increasing the reaction time of the trailer braking system. This may kid you into believing that the brakes are less aggressive .... in actual fact all you are doing is delaying their action and (in most instances) stopping them from doing very much at all.

Remember, if you fit a simple orfice plate-type line restrictor in a single-acting hydraulic circuit, it will also delay the rate at which the trailer brakes release AS WELL as how quickly they apply. All of this, together with fairly cold, thick oil in small diameter pipes, is bad news.

All-in-all Spool Valves are a very, very primitive way of trying to control a trailer's brakes ..... because they work by controlling oil flowrate (quantity) rather than by controlling pressure ....... which is what's needed in a braking system. If you've no option other than to use a spool valve (other than chucking an anchor & chain out of the back of the cab), at least put a pressure reducing valve between the spool valve & the trailer and set the max pressure to no more than 150 bar / ~1500 psi. That's another reason why trailer brake rams don't work well off spool valves .... they're not designed to operate at the ~2500 psi produced by most tractor hydraulic systems.

Bosch and a number of other hydraulic companies (e.g. Rexroth & Husco) made pilot-operated hydraulic trailer brake valves back in the day. The serial nos should identify whether they were intended for use with brake fluid or mineral oil. As Rick has said, those fitted to MF 600 series tractors & similar MF models from the early-1980s onwards used 'brake fluid' as opposed to mineral oil actuated service brakes & so would work with Leyland hydraulically-actuated tractor brakes. But make sure you put a pressure gauge on it when finally installed & check that you are getting a half-decent (>100 bar) trailer brake coupling output before you have to stand on the brakes!

APH463
Posts: 4
Joined: Sun Apr 01, 2018 5:07 pm
Great Britain

Re: Trailer brake

Post by APH463 » Sat Mar 30, 2019 5:11 pm

All that I can tell you is that back in the 80's trailer brake kits were an extra when you bought a new tractor so this meant that not every tractor had trailer braking so you had to use the spool valves. The firm that I worked for back then grew 1000 acres of potatoes in Wiltshire / Berkshire all of which had to be hauled back to the store, as you will know Wiltshire is not at all flat . WE could have up to 15 or so, 8/10tonne trailers hauling back to the store and maybe up to about 6 of the older tractors didn't have trailer brakes , you have a few options when coming down some of the steep hills, use the gears on the tractor to change down (OK unless its a ford tw) slip into four wheel drive if the tractors got a switch on the dash or use the spool valve . Hydraulic brakes on the trailer end will have at least 2 springs on to pull the brakes off and the ram back and on a spool valve brakes are on or off not very often you had time to be gentle , so that was our solution OK 3/4mm would be a bit small but you just work out what size the hole should be. The other thing was that at that time the police would often check loaded trailers to see if the brakes worked so again you needed your spool valve if you hadn't got the fitting on the brake system on your tractor. The other thing is that you did have to drive the tractors , use your gears , and brakes just to be sure you could stop . Tractors that we used on the job could be ford , john deere , MF or zetor any way you drive a zetor 11245 with a 10 tonne loaded trailer on and you want know you can stop, as I say it worked for us may not be quite the thing now but it was then for us. A day for our drivers would be in the field harvesting at 7.00am if they were on a long haul back to store they could be doing a 50/60 mile round trip and do 3 loads a day , the later starting drivers would do 2 loads a day on that mileage and be loaded ready to tip the next morning, we did well and not to many mishaps . Phil

Jazo
Posts: 37
Joined: Sat Mar 31, 2018 5:51 pm
New Zealand

Re: Trailer brake

Post by Jazo » Sat Mar 30, 2019 9:49 pm

Hi, I think Rick had a setup that used a pressure relief valve that plugged in a spool and a dump line. And just adjusted the relief pressure according to the load on the trailer
3/45 with faster reductions and turbo

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