FridgeFreezer Posted September 28, 2009 Share Posted September 28, 2009 This is only the seed of a silly idea related to the seed of another silly idea, but I'm interested to hear what people think... I am looking at using a transfer box (possibly LT230, possibly something else) as an in-line overdrive or splitter on a potentially chunky piece of machinery to raise the RPM of the output shaft. Basically it would be sitting in the middle of a propshaft and running in reverse so it is raising the revs by 1:1.222 or whichever range I end up with. A G-Wagen box has also been suggested as they are divorced (prop in, prop out). It needs to be fairly close gearing, like an overdrive (+25% or +30%) rather than the 3:1 drop the LT gives between high & low, the G-Wagen is closer at 2:1 with the bonus of synchromesh so it could be engaged/disengaged on the fly, but still not ideal due to the large ratio step. So, the questions are: - Is there some inline box that does this job in another vehicle or machine already? - Is there an issue with running the LT230 or indeed other transfer cases full-time in reverse? - Is there a better suggestion than the LT or G-Wagen box (I think SJ may be a bit small) Quote Link to comment Share on other sites More sharing options...
Superpants Posted September 28, 2009 Share Posted September 28, 2009 A bit of a hypothetical answer as I'm not familiar with the innards of the boxes you are suggesting, however I would take a close look at how the lubrication is arranged. If it is by pump, then driving the output could mean no lubrication when in neutral. If it is by oil bath, will the oil reach where it is supposed to? HTH Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 28, 2009 Share Posted September 28, 2009 You may have thrust bearing peoblems with helical gears. I worked out that in a series gearbox in drive the gears push towards each other, in overrun they push apart loading the thrust bearings. I stripped the splines off a SIII gearbox mainshaft when I tried to bump start a mis-timed Perkins 4203 Quote Link to comment Share on other sites More sharing options...
Daan Posted September 28, 2009 Share Posted September 28, 2009 You may have thrust bearing peoblems with helical gears. I worked out that in a series gearbox in drive the gears push towards each other, in overrun they push apart loading the thrust bearings. I stripped the splines off a SIII gearbox mainshaft when I tried to bump start a mis-timed Perkins 4203 depends which direction they turn. Plus, I know the input gear has the bearing size the same on both ends, so no problem there. Not sure about the output gear, may be worth taking a look inside. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 28, 2009 Share Posted September 28, 2009 depends which direction they turn. Plus, I know the input gear has the bearing size the same on both ends, so no problem there. Not sure about the output gear, may be worth taking a look inside. That's the point, assuming a gearbox is designed to run one way, running it the other way may wear the thrust bearings. I reckon thrust will be increased at both thrust bearings if the box is run the other way, not just changed from one end to the other. Quote Link to comment Share on other sites More sharing options...
Jon White Posted September 28, 2009 Share Posted September 28, 2009 John, Have you looked at the Milner ones? Shaft in and shaft out etc and quick change ratios. Commonly used by the Safari racing boys so should be pretty strong! Jon Quote Link to comment Share on other sites More sharing options...
Lara Posted September 28, 2009 Share Posted September 28, 2009 I would have thought that the box would run perfectly satisfactorily in reverse as it should not give any different forces than lifting off from speed, or heavy engine breaking etc! Both put reverse thrust through the box! And I am sure Landrover designed for this! although maybe not constant! Or something like this if you have the budget! http://www.lencoracing.com/CS3MasterPage.html Lara Quote Link to comment Share on other sites More sharing options...
Daan Posted September 28, 2009 Share Posted September 28, 2009 John, Have you looked at the Milner ones? Shaft in and shaft out etc and quick change ratios. Commonly used by the Safari racing boys so should be pretty strong! Jon They reverse the rotation though, which wasnt what john was after I think. And they cost big money which isn't normally what HOFS are about... Anyway, it would help if you tell us the application so we can be more specific. Plus we are dying to know what you are planning Daan Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 28, 2009 Author Share Posted September 28, 2009 I knew I shouldn't have posted - as I said, this is hypothetical tweak to a hypothetical seed of an idea and nothing to do with exciting new builds. Basically, imagine you have a big engine/turbine/water wheel/windmill/genetically mutated gerbil in a wheel which turns a propshaft to power a huge mechanical doomsday device and/or kitten stroking machine at a certain speed, and you want to multiply the output RPM by a bit to match the speed/power for optimum doom/fluffy kitten joy. Power handling & RPM needs to be similar to what a transfer box can handle - there are a lot of unstroked kittens out there. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 28, 2009 Share Posted September 28, 2009 Could you find a kitten better matched to your gerbil and abandon the transfer box? Quote Link to comment Share on other sites More sharing options...
Mark Posted September 28, 2009 Share Posted September 28, 2009 Have you tried boring the kitten, rather than stroking it to get more power??? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 28, 2009 Author Share Posted September 28, 2009 Have you tried boring the kitten, rather than stroking it to get more power??? The RSPCA told me it wasn't allowed Quote Link to comment Share on other sites More sharing options...
Aragorn Posted September 28, 2009 Share Posted September 28, 2009 Does the box actually have to turn backwards? It could turn in its normal direction, just with the power being fed in the output flange could it not? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted September 28, 2009 Share Posted September 28, 2009 Does the box actually have to turn backwards? It could turn in its normal direction, just with the power being fed in the output flange could it not? That's what the OP suggested. This means effectively it will be working in overrun permanently, hence my concern about thrusts. If it was in reverse and back to front it should be OK. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 28, 2009 Author Share Posted September 28, 2009 Does the box actually have to turn backwards? I haven't solidified that part of the vapour-plan yet, I would have to check if it's a clockwise gerbil or not. The term "reverse" was meant as running power in through the output of the transfer box, rather than the direction of rotation. Quote Link to comment Share on other sites More sharing options...
Lara Posted September 28, 2009 Share Posted September 28, 2009 Well if you use "Moggy" axles it will fit with your Pussy stroking plans and also help with being able to use reverse rotation! Lara Quote Link to comment Share on other sites More sharing options...
steve b Posted September 28, 2009 Share Posted September 28, 2009 Hi FF How about an old boat gearbox ? one from an old twin lister/Kelvin which only rev to about 1000rpm would probably be geared up to give the right prop speed. Or a vari-belt drive off an old Combine harvester? Having said that a mate of mine that built himself a 6x6 RRC had a 2nd T/box driving the rear 2 axles going in through the front o/p and out through the rear o/p and a modded input (bearing housing & shaft with prop flange) , which seemed to work ok cheers Steveb Quote Link to comment Share on other sites More sharing options...
pat_pending Posted September 28, 2009 Share Posted September 28, 2009 Don't mess about with Land Rover related stuff, what you're after is readily available on trucks, plant, agricultural machinery, production lines etc. From self contained epicyclic boxes to chain drives. I imagine you don't want to spend loads, you just have to find the right scrap yard. For an idea of what's available new though, have a look here. You'll have to register. Quote Link to comment Share on other sites More sharing options...
Night Train Posted September 28, 2009 Share Posted September 28, 2009 How much power and torque do you need to transmit? you could get a Laycock overdriveand build that in line. It would be electrically switchable from direct drive to overdrive. You would need the input to it so maybe getting the gearbox and overdrive together would make things easier. Just cut the back end off the gearbox and mount a flange on the left overs of the mainshaft. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted September 29, 2009 Share Posted September 29, 2009 A standard car gearbox would probably also work. A lot of car trannys have overdrive 5ths anyway, some diseasls have overdrive 4th and 5th, and that would negate the requirement of power flowing thru it backwards. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 29, 2009 Author Share Posted September 29, 2009 How much power and torque do you need to transmit? About 1000 kitten-meters (OK, up to 1000nm / 200kW up to 2500rpm). It should push the freelander along quite nicely Quote Link to comment Share on other sites More sharing options...
Night Train Posted September 30, 2009 Share Posted September 30, 2009 That is a fair amount of power to transmit There are Jag overdrive gearboxes that may be able to handle that sort of power and torque. Also some of the big Fords from the 70s and 80s used a similar overdrive and are a lot cheaper then Jag ones. Is it worth describing what you are doing in more detail? Is it a vehicle or a machine? Is there drive speed variable or fixed? Will there be any shock loading or start up load? There may also be agricultural, marine and industrial gearboxes that may be usable. A search on Ebay brings up lots of potentials. I even found a straight cut spur gear box from a tractor that would probably run backwards (turning it around would still load the gears the right way) and a part stripped Unimog box that might have enough parts left. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 1, 2009 Author Share Posted October 1, 2009 Is it worth describing what you are doing in more detail? TBH I'm not sure it is, the suggestions so far have been good and frankly the idea is pretty vague anyway. Adding details about something which may never even happen is a bit too vapour-build for me, and from there it's only a matter of time before someone sidles up to me in the pub and asks about the lightweight racing combine-harvester that so-and-so says we're building It is a vehicle powertrain and I believe the rotation of the engine is clockwise-viewed-from-the-rear (which I think is the same as most engines?), I don't have much more than that currently. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted October 1, 2009 Share Posted October 1, 2009 Most engines run clocwise viewed from the front. I had a Proton which ran the other way (by design! the gearbox was on the right of the engine, viewed from the driving position) Quote Link to comment Share on other sites More sharing options...
Aragorn Posted October 1, 2009 Share Posted October 1, 2009 With torque figures like that it sounds like an electric motor? The only other way you'd be getting 1000nm and "only" 250kw would be with a large diesel, perhaps a truck/bus engine? Cant really see you installing 600kgs of Volvo D7C into a passenger car though! Quote Link to comment Share on other sites More sharing options...
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