Challenge vehicles: gearing, winching and driving

[RichardD]

This is a puzzle I've been gnawing at for a while: how best achieve a cost effective balance of winching and driving speeds for challenge vehicles. Obviously this applies to all 4x4s with winches but the problem is more critical for challenge trucks and boils down to gearing of one kind or another.

Here is the essence of the problem:
If I'm winching over ground where there may be a decent amount of traction in places ideally I need to keep revs at say 1500rpm to maintain power to the winch but this means that the wheels will be spinning much faster than the winch can provide forward motion. If I find some grip I could break the halfshafts or the winch/rope as I lose it again.

I could spend £3,000+ on a twin motor 8274 or redwinch to get the line speed but that is unaffordable for most, or I could change the gearing in some way to reduce the wheel speed to match the winch speed at 1500rpm but how to best do that without spending £000s?

1. fit smaller tyres. Yes, but then I lose ground clearance!
2. fit a crawler transfer box and bounce between high and low as needed
3. fit a 2nd t/f box and solve the short rear prop problem

Given my buggy is TD5 90 based who's got ideas that will cost less than big ass winches.

[RichardD]

I've looked at Ashcroft's excellent underdrive which, they tell me, is back in development and available soonish but at a cost of about £2,500 by the time you add in the extras you're into big winch territory.

I'd prefer a gearing solution to a winch one for reliability but that increases the total build cost of the truck by nearly 25%

[Xpajun]

Spending on a winch isn't really adding to the cost of the truck - at the end of the day you can take the winch onto your next build - or even sell it separately.

Of course you could always fit capstan drums to your front wheels:



But I can't see any cheap way to match drive output to winch speed - one of the biggest problems with pto winches.

Best I can advise is revs when full reliance on winch is needed then drop back the revs when you have drive - don't forget the winch won't be taking as much power then

[bigbuggy]

you either need to increase the gearing of the winch, or lower the wheel speed,

so realistic options are either drop the diff ratios to 4.11 or go for a faster winch,

im currently running 4.11 diffs with a 1.4 transferbox 37" tyres, with a twintop 8274 with +60 gearing

[cynic-al]

Run an auto and you can left foot brake to control the wheel speed. Obviously if your doing it a lot and hard you might need to upgrade he stock oil cooling and brakes.

Are you sure keeping your revs up is actually achieving that much? The actual difference in output of the alternator at 1000rpm compared to 1500rpm in relation to the current the winch is drawing will be a drop in the ocean I'm sure. If your struggling for battery life add more batteries and alternators.

[big_patrol]

What about using a different set of pulleys to re gear the alternator?

[dxmedia]

PTO winch.

They tend to be designed to match the road speed of one of the forward gears.

[bigbuggy]

[lambert]

What about a second high output alternator and a separate odesy just fo the winch that way you have loads of current at low ish rpm?

[bigbuggy]

the winch wont physically go an faster even if he went down that route, if richard was gonna go for that option he would be better off, fitting a 24v alternators & overvolting his current winch

[big_patrol]

He doesn't need a faster winch if his car will provide the charge at lower revs hence why I suggested getting it spinning faster.

[lambert]

No I was meaning that if Richard is revving to get the juice out of his current alt which is making the wheels spin then a separate alt giving more juice at lower revs means he will have lower wheel speed

[teamidris]

Engine driven PTO pump and a gearbox PTO with a motor
http://www.youtube.com/watch?v=G9C1-clYaVI

But auto works for us.

The cheapest option is a PTO winch made from a diff. Some fab and head scratching required though..........

[cynic-al]

You need to be cautious altering the pulley sizes of the alternator otherwise it might end up spinning too fast when you rev the engine, although I guess diesels don't rev as high as petrols in the first place.

[bigbuggy]

a TD5 revs fast enough in standard issue to cause problems with throwing belts,

td5 in mine has been to 4600 a few times

we run 2 alternators & 2 steering pumps & have had issues with throwing belts off due to mud ingress on the pulleys,


but that all aside, the easy answer would be to either slow his wheels down, or speed the winch up,

simple answer being either an 8274 or fit 4.11 crown wheels & pinions

[RichardD]

I've got a bit more time this evening to explain myself a little more clearly, all the better for a long chat with Mike (bigbuggy) about the effects and options.

One problem I have is that, for all my technical knowledge, my maths is seriously pants so I have real difficulty in doing gear calculations so I'm on 'conceptual' only here.

NOTE: winches are TDS goldfish 9500's with 55mmsq welding cable wired direct to the batteries (twin, big) via isolators on +ve

Empirically, I've found that heavy winching at tickover works fine but as soon as I bring the revs up a little the winches run noticeably faster. This means the wheels have to spin rather than turn which, to my mind, means I am not able to use the vehicle effectively to make best use of available traction (if any). I also run the risk of axle tramp (bouncing) causing a breakage.

Agreed, I can use an 8274 like everyone else but I don't/can't spend £1000+ on a winch alone. I have a cracking comp truck that was built on a reasonable budget and this discussion should be relevant to those on minimal budget (whcih I now find myself on).

So, after chatting to Mike, it seems that going for 4.11 diffs will reduce the gearing by ~15% which will shatter the top speed (not an issue as I can use high box for higher speeds - moving linkage for ease could be a challenge) &/or allow me to use larger tyres. Underdrive is a waste of money for me so that's out.

So now do I buy new ring and pinion gears and learn (or pay for) a rebuild or splash out on new diffs .... will have to wait until after I pay for the roof repair, new back door, 2 rescue cats and the damage they'll cause, 4 more ducks, ..... Thank god I don;t have Xmas to worry about!

[teamidris]

We've got a fast winch and auto and it's still an issue if I bring the revs up. It's an easy fix with 2 engines and not much else gets you around it.
I'm concerned changing the diffs will help, but not get you to what you would like?
There was a twin motor kit kicking about the net on a goldfish. (end to end)

[dxmedia]

24v when the winch is under load?

[RichardD]

Everything is a compromise. I'm looking for something that gets me closer to the 'ideal' without spending thousands.

If I had the cash I'd have 2 gigglepins/redwinches, crawler box and massive engine/autobox. I'd also be immensely attractive, have a spare Ferrari and have a successful business obtaining PPLs for pigs

[dxmedia]

Link

[.]

Is the simple answer, don't spin your wheels and let the winch do the work? works for me!

[RichardD]

[will4x4]

this is not a problem to spin your wheels.

it is when crawling steep banks however.

I use a saley hydro winch and just slip my clutch when required for 3-5 seconds .

[chal3oye]

I can use an 8274 like everyone else but I don't/can't spend £1000+ on a winch alone. I have a cracking comp truck that was built on a reasonable budget and this discussion should be relevant to those on minimal budget (whcih I now find myself on).

So, after chatting to Mike, it seems that going for 4.11 diffs will reduce the gearing by ~15% which will shatter the top speed (not an issue as I can use high box for higher speeds - moving linkage for ease could be a challenge) &/or allow me to use larger tyres. Underdrive is a waste of money for me so that's out.

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