pugwash Posted October 10, 2006 Share Posted October 10, 2006 I have just done some numbers and want some experience and opinions. My theoretical dream motor can do 2.2mph in low first at 1750 rpm, a hydraulic PTO winch will be pulling at 26ft/min (or 9meter/min) at that rpm. By my calculations the car will be trying to drive at 58metre/min with the winch pulling at 9m/min My wheels will be turning 6 times faster than they should for a true 1:1 drive assist. How much of an issue is this going to be? I would say not very much but what does everyone else think? Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 10, 2006 Share Posted October 10, 2006 Yes Jim it is an issue when your winch speed is tied to your transferbox speed……….probably less of an issue (but still an issue) when the winch speed is tied to your engine speed. Hell, I’m busy at the moment but quick calc tells me 88ft/min=1mph When my winch is doing 40ft/min (0.45mph) ……….. the wheels will want to be turning at 12.94mph………………. Whilst I realised this when I built up the winch, I normally will only slightly drive assist over an obstacle, like a step or a tree root……….. even then its not entirely necessary. Drive assist is OK …………. But it has its place in the armoury and is not always a prerequisite …………. Commercial winching practise frowns heavily on drive assist. In your calculations the vehicle wheels will be turning at 193.6ft/min and the winch will be recovering line at 29.5ft/min …………… Ian Quote Link to comment Share on other sites More sharing options...
Mark90 Posted October 10, 2006 Share Posted October 10, 2006 8274 and an auto box Quote Link to comment Share on other sites More sharing options...
will_warne Posted October 10, 2006 Share Posted October 10, 2006 8274 and an auto box Ditto. I found that since I've moved to auto I'm able to winch much faster. IIRC the way coefficients of friction work in the real world is that you reach an upper limit before wheels spin and then the value drops off. In other words you'll get more assistance if you're not spinning you're wheels but matching the speed exactly with the autobox or crawler gearset. That said, spinning wheels does help a lot on pulls. The technique I found worked best when I was running manual (and with gearing that was way out) was to feather the throttle which seemed to give reasonable results. However, its no match for total drive assist. The problem I found was that on sand the vehicle would dig in at the top of the hill climb as the nose was pulled down. With auto (or equally low gearing) you're able to stop you'reself digging like this. Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 10, 2006 Author Share Posted October 10, 2006 Mark- you're not helpful. Blooming 8274s. Ian- you have lost me. What i have at the moment is a ratio of 1.8mph per 1000rpm in low first. does this make low first slower or faster than my winch? Quote Link to comment Share on other sites More sharing options...
Mark90 Posted October 10, 2006 Share Posted October 10, 2006 Mark- you're not helpful. Blooming 8274s. Sorry I just thought I'd introduce the 'other' option as is traditional in any winch thread. Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 10, 2006 Share Posted October 10, 2006 Jim, It depends on the speed your pump shaft needs to turn in order to provide the correct flow. PTO on the Xfer box is effectively the output of the gearbox ……….. therefore, for my pump to turn at 2000rpm the gearbox would be in 4th (1:1) In first gear the pump would only turn at 555rpm for 2000rpm engine speed (3.6:1) I run the x/ferbox in neutral when winching ……… just flipping into low plus some clutch slip if I need a little drive assist........ this is rare HTH Ian Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 10, 2006 Author Share Posted October 10, 2006 god i'm so dense- i knew i was missing something blindinly obvious- i was of course missing the small factor that there is a gearbox in between the transfer box and the engine- DOH. So my pump wants to be running at 2600rpm to get maximum flow- and i want to work out an engine speed which equals 12mph at the wheels with a multiplaction of 2600* a relevant gear. Using Mark 90s calculator i get: Use Second Gear on an autobox at 1.48:1 At 3900rpm the PTO will be rotating at 2600 rpm so delivering maximum speed and pressure At my proposed axle and tyre ratio i will be getting a wheel speed of 11.9mph at 3900rpm in low second. this would make second low for me "pefect" for drive assisting wouldn't it or am i being stupid again? Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 10, 2006 Share Posted October 10, 2006 In theory yes …………. but it will never be perfect because the winch is pulling you at 0.4mph and the wheels want to travel at 12mph. To get perfect drive assist you either need to have a very high volume pump that delivers the flow at low rpm …….. or a very f’kin fast winch ……1047ft/min. Either way its never going to be perfect …………… Ian Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 10, 2006 Author Share Posted October 10, 2006 yeah i understand that- i'll just use low first instead and rev the nuts off the motor when i want to drive assist. or just go electric again. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 10, 2006 Share Posted October 10, 2006 So my pump wants to be running at 2600rpm to get maximum flow- and i want to work out an engine speed which equals 12mph at the wheels with a multiplaction of 2600* a relevant gear.Using Mark 90s calculator i get: Use Second Gear on an autobox at 1.48:1 At 3900rpm the PTO will be rotating at 2600 rpm so delivering maximum speed and pressure At my proposed axle and tyre ratio i will be getting a wheel speed of 11.9mph at 3900rpm in low second. How many horse power is that at full flow/pressure Jim? Chris Quote Link to comment Share on other sites More sharing options...
Paul Wightman Posted October 10, 2006 Share Posted October 10, 2006 Jim, is it your plan to use drive assist on the 1st, 2nd, 3rd or 4th wrap on the drum? Maybe a little 4 speed gearbox on the pump drive and a laser tracking dingbat on the drum to guage the rope height? Quote Link to comment Share on other sites More sharing options...
BogMonster Posted October 10, 2006 Share Posted October 10, 2006 Sorry I just thought I'd introduce the 'other' option as is traditional in any winch thread. Equally traditional is for somebody else to then turn around and go <slap> Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 10, 2006 Author Share Posted October 10, 2006 Jim, is it your plan to use drive assist on the 1st, 2nd, 3rd or 4th wrap on the drum?Maybe a little 4 speed gearbox on the pump drive and a laser tracking dingbat on the drum to guage the rope height? yeah ok don't take the tiddle i was only idly trying to do some doodles at work and got my little brain totally confused about all the different calculations i was trying to work out! Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 10, 2006 Author Share Posted October 10, 2006 umm quite a lot really. do you mean HP in the hydraulic system or HP of the engine? either way it's going to be quite a lot- Ian (bullbar cowboy) or Nige would be better able to answer this as i haven't a clue really- i remember working out one day that maximum torque at max PSI and flow is 504nm which i think is 372lb/ft of torque. But don't quote me on that Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 10, 2006 Share Posted October 10, 2006 umm quite a lot really. do you mean HP in the hydraulic system or HP of the engine? either way it's going to be quite a lot- Ian (bullbar cowboy) or Nige would be better able to answer this as i haven't a clue really- i remember working out one day that maximum torque at max PSI and flow is 504nm which i think is 372lb/ft of torque. But don't quote me on that I was wondering really if such a pump could be driven from the crank. I know V-belts are not much cop for higher torques but how about a toothed belt or a chain, would that work? That way you could gear the pump to offer optimum flow etc. at, say, 2000RPM and then slip the clutch from there to get some drive assist. Or is that a bad idea? Not gonna do the clutch any favours I suppose. Chris Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 10, 2006 Share Posted October 10, 2006 A better way to drive assist would be to add an engine driven pump (like the ZF74 or larger) and then use manual valves to switch between PTO and/or ZF74. Yet another option is to plumb in an auxiliary electrical driven hydro pump…… however I haven’t seen any within the automotive world that quite do the trick……… but there are some that are used on forklifts that may be of use. However, with any of the above options you are introducing complex plumbing and more to go wrong ……….. For true drive assist it would be hard to beat a low ratio crawler box and a fast electric winch…………. without a lot of complex design issues you cannot have the winch speed tied to the wheel speed. Paul W once posted an excellent analogy ……… but I cant remember it exactly. Ian Quote Link to comment Share on other sites More sharing options...
Paul Wightman Posted October 10, 2006 Share Posted October 10, 2006 Paul W once posted an excellent analogy ……… but I cant remember it exactly. Nor can I Quote Link to comment Share on other sites More sharing options...
dollythelw Posted October 12, 2006 Share Posted October 12, 2006 I was wondering really if such a pump could be driven from the crank. I know V-belts are not much cop for higher torques but how about a toothed belt or a chain, would that work? That way you could gear the pump to offer optimum flow etc. at, say, 2000RPM and then slip the clutch from there to get some drive assist.Or is that a bad idea? Not gonna do the clutch any favours I suppose. Chris Thats how a Type R works Chris, dog clutch to bring the pump online so you are only robbing power when you need it - it works very very well... if you want quick mech PTO with 1:1 winch speed/drive speed try this Robur or put up with slow hydro Type R Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 12, 2006 Share Posted October 12, 2006 - it works very very well... Because the winch speed is divorced from the wheel speed...................... Ian Quote Link to comment Share on other sites More sharing options...
white90 Posted October 12, 2006 Share Posted October 12, 2006 8274-xp motor-ashcroft underdrive-3.54 diffs low low 1st is the same wheel speed to a hard pull on the winch. contrary to Wills post spinning the wheels whislt winchinfg appears bugger all use to me. spining wheels by revving on sat actually slowed the progress of the vehicle letting it tickover and the wheels turning to match the winch got the vehicle out far quicker. thuis was o repeated winching not just at one punch. Quote Link to comment Share on other sites More sharing options...
dollythelw Posted October 12, 2006 Share Posted October 12, 2006 8274-xp motor-ashcroft underdrive-3.54 diffs....low low 1st is the same wheel speed to a hard pull on the winch. bag of sugar up hill then ? [tin hat time again] Quote Link to comment Share on other sites More sharing options...
white90 Posted October 12, 2006 Share Posted October 12, 2006 well a lardy Bag perhaps 2105kg 50degree slope. this one(yes I know it isn't a bottomless swamp) but I couldn't drive it/stop collect punch and reverse in one so a winch was req James or Will had a speread sheet that expalined the actual gearing on those diffs with underdrive I can't find it at present. PS Jim what will this Rangie tray back on Mog axles plus hydraulc winches fully kitted weigh, any proposals? PPS Jez when will you be bring one of your creations out to play then? HBRO may be a good one to sign up for. perhaps a moglite/petal team entry? Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 12, 2006 Share Posted October 12, 2006 There is winching and then there is winching …………. The former could be considered as unnecessary and caused by bad driving………… and the later is because one is seriously stuck and up to the eyes in poo. In this situation spinning the wheels whilst winching will just dig bigger holes and make it harder to winch. Yes……… low crawler and a reasonably fast winch has to be the best combo for true drive assist. Ian Quote Link to comment Share on other sites More sharing options...
white90 Posted October 12, 2006 Share Posted October 12, 2006 maybe a Type R if running Rover gear on 3.54s Mogs no idea but a type R would appear to fast for wheel speed or would it? Quote Link to comment Share on other sites More sharing options...
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