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Building a fast hydraulic winch


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#1 white90

white90

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Posted 08 June 2006 - 06:27 AM

By popular demand …………. :P
After many years of using electric winches in my profession, when I re-built the 90 I decided to go hydraulic using the Milemarker 2 speed. Generally hydraulic is bomb proof if installed correctly. However, the MM has a bad reputation here in the UK for being slow ……… but this is only partially true as many folk never appreciate that a hydraulic motor fed from a fixed flow pump will always turn at the same speed up to its maximum load. In fact the MM is way quicker at full load than most electric winches, but fails miserably against them in the light /low load spool time.

My original setup used an engine driven ZF74 pump and small tank …. So after 3 years, its time to go major league.

The motor on the UK imported MM is a different spec to the US model. Stateside gets the 17.9Cu in and we get the 12.5Cu in. The characteristic of these motor are similar but not identical. For our application the 12.5Cu in motor is the better option. Looking at the specs for the Whites Hydraulics 200 series motor we get the following,

Continuous Flow 16 US/GPM

Max Flow 20 US/GPM

Continuous Pressure 1750psi

Max Pressure 2250psi

Continuous Shaft RPM 300

Max Shaft RPM 370

Max Torque 3050in/lbs

So…… the drum is 2.5ins diameter (1st layer) so 1 RPM of the drum is 7.8ins. The MM is 6:1 so therefore the absolute Max line speed (in ft/min) at full load calculates out as ((370/6)*7.8)/12 = 40ft/min. By the time you get up to the third layer the winch will be doing over 50ft/min

In high gear (respool mode) the MM operates at 1:1 so the Max line speed will be (370*7.8)/12 = 240 ft/min.

In reality those speeds will be too fast for general use so we need to carefully select a pump that will match the requirement.

For this application the pump that I have used has the following specs,

Capacity per Revolution 25cc (25L/min @1000rpm)

Min RPM 650 (16.25L/min)

Nominal RPM 1500 (37.5L/min)

Max RPM 2500 (62.5L/min)

Max Pressure 2325psi
The MM winch body is really well made and capable of a lot then is published by MM. The parts of the supplied system that let it down are,

1) The design was to run from a steering pump. IMHO this will always be compromise because of the flow curve of this type of pump.

2) The solenoid spool block will only flow a max of 3.5US Galls/min. This would be a serious bottleneck on any system upgrade

3) The whole system is piped in 3/8 and this would be unsuitable for the required flow rates as detailed above.
My view of the way forward is to use a PTO driven pump, a manual spool valve with built in PRV, a tank of at least 1:1 capacity an over-centre valve in case of pressure loss, and an in cab pressure gauge to show what the system in doing.

The piping will be 1inch from tank to pump, Ύ inch return, and ½ inch feed to the motor
Calculations like the above are never difficult…………. but defining the parameters for the calculation can be really difficult :rolleyes: .

I suppose the most difficult area was defining in ft/min the winch speed. If I ran a winch and said to 10 experienced off road guys, “tell me what speed that was in ft/min”…………… I would get 10 different answers and probably none of them would even be close. With an electric winch as the load is increased, then the motor note changes and the winch slows and the converse is also true…………. with increasing the load on a hydraulic, the speed stays exactly the same until the pressure reaches the PRV setting. Then the winch just stops. So, to give me a real feel for what is fast and what is slow, and what is acceptable, I looked at several electric winch specs and compared these to my calculations. In every case the calculations showed the Hydro / pump setup to be very much faster……….
The UK MM importer builds a MM derivative (called a MM type R) that spools, under full load, at over 75ft/min. This design uses solenoid valves so its either ‘on’ or ‘off’ with nothing in between and also uses an engine driven pump via an open chain. Before we get all cynical about the chain, it is designed to be connected when the winch is required and not a permanent fixture. To be fair, this winch was designed for competition use……. but to me, for general use, that sort of speed would be mighty dangerous. That’s why the design I have finally used incorporates a manual spool valve for fine control, plus the ability to select any of the forward gears (with the transfer box in neutral) to vary the maximum pump speed.

Winching with hydraulic is very deceiving …...….. the winch just keeps on turning at the same speed and applying the power, until either something gives or the system pressure trips the PRV (pressure relief valve). This is a reason why you need very strong mounts and super strong recovery points.

As long as you appreciate the power of hydraulic, they are a joy to use ………. they go at the flick of a lever and they stop dead at the flick of a lever……… with hydraulics you get no run on.
So what was the most difficult part of the installation ………… without any doubt this was the routing of the hydraulic pipes and ensuring enough room for the size of the hydraulic fittings. I have used very high quality double walled ‘megaflex’ rated to 29Mpa (4200psi). Even a compact 90 on 1 inch pipe is massive …….. then add that to the fact that you cannot twist 1 inch pipe, so the fittings need to be crimped on once the lay of the pipe is sorted out. The only real fabbing was the tank mounts ……. and I made up these from some pieces of 8mm steel. The other area of fabbing was the winch bumper ….. this was a preproduction model that was made by a well known small workshop near here for a local 4x4 aftermarket part supplier. I bought it cheap because (a) the angle of the A bar was wrong……. it was leaning toward the grill instead of away from the grill, (B) the tubular bumpers were the wrong angle …… well, they were for me, and © the whole assembly had a 10mm twist in it. After a lot of grinding out welds, cutting and re-welding I have obtained the result I wanted. My son then painted (sprayed) it with black engine bay 2 pack.
The final setting up is simple ……… after filling the system, run the pump to purge the air. Then adjust the OCV (overcentre-valve)….. for this application it needs to be set very light, so unscrew the adjuster all the way out and then screw in until spring pressure is felt (about 4 turns). Next is to set the PRV………… mechanically lock the winch by selecting high and low gear together………….. back off the PRV adjuster……… then operate the winch and quickly adjust the PRV to 2000psi on the gauge.

For those that are not familiar with hydraulics, the OCV (Over Centre Valve) is a fail safe device. Its a ball bearing shuttle valve and the idea is that if you suddenly lose pressure (maybe a broken or split hose) then the shuttle operates and blocks off the go & return motor ports. This hydraulically locks the winch………. this device is a ‘must have’ if you do a lot of winching up hills or lowering out on steep slopes.
So…………….. here is the install in pictures,
The assembled bits look like this

Maxidrive Rover PTO housing, pump, and overcentre valve

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Tank

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This is the 20micron return filter on the tank

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Spoolvalve – these are used on forklift trucks

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So…off with the old

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And then strip the winch that has been on the front for over 3 years and has been underwater many, many times and also has seen sea water. The strip down is easy, just undue the tie rod set bolts and pull off the gearbox & main shaft. I was well pleased too find no water ingress and the gearbox was like new. As you can see the centre shaft on these is massive. All this needed was re-greasing with waterproof grease and a coat of paint.

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Tank in the load bed

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Spool valve beside the driver

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Pump and housing onto the transferbox

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The PTO dog clutch lever

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Bling pressure gauge in front of the spool valve

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Overcentre valve as close to the winch as possible.

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And then the plumbing

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The winch bumper is a whole new story...

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The final testing has exceeded all expectations ……. Continually variable from silly slow to very fast. Respool in high gear is now a joke ……… you could respool the whole 100ft drum in 20seconds. I need to do some load testing, but I have set the PRV to 2000psi, so I have calculated that the winch will trip the prv at about 16000lbs on a single line pull.

But unlike electric ………. You can pull that 16000lbs at up to 40ft/Min and all day long

David Lovejoy gave me a hand to spool up the plasma …….I think he still has fingers :lol: :lol:

We found that 1000rpm in 4th (1:1) with the winch in Low was plenty fast enough for Dave’s fingers :D . Using the motor manufacturers published data this works out as ((147rpm/6)*7.8)/12 = 16ft/Min ……… OK 15.9 rounded up
Well, I got to do some unplanned load testing at the weekend ………. Saturday night is the time we shoot rabbits on a 300 acre farm……… my son stands in the back of the defender with his 3 shot auto 12G Beretta and I drive & light up the rabbits with the 700watts of spot lamps whilst also waving a 12G under/over Browning out of the window :ph34r: . At about midnight I drove through a area of natural clay bog ………. we normally avoid this but as it has been very dry I thought I would be OK. About half way through I sank to the chassis ( I wasn’t trying) ……… using an extension rope I hooked up onto a tree at about 150ft ………… the extraction was effortless and I noticed the pressure gauge was indicating about 900psi ……..driving around this farm is always quite challenging as it is very hilly terrain with some woodland & grassland slopes ……… and I get to go wherever I want :D .
It a bit long winded .............hope you're not bored.

Edited to add ......... i really should have cleaned the truck before I took the pictures !
Ian
Tony


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