Vapour overdrive project.

[bill van snorkle]

Initially I got excited by the idea and then reality came and smacked me in the mouth, as I am not sure there is a gearbox out there that would have suitable gearing to lend itself to being an actual splitter box in terms of mid range 1-2-3-4 split top 1-2-3-4, or could it be dome through the actual gearing within the transfer box itself?

Not sure if you would like to do some ratios for the mid and top boxes Bill as I think that might be a nice solution with maybe using an R380 as primary gearbox?

IMO,hardly anyone would be interested in a splitter/overdrive box that involved shortening the rear propshaft, lengthening the front one, altering transmission mountings and relocating crossmembers to install. So our Vapour Splitter necessarily needs to be of the piggy back Fairey/GKN PTO driven type of design.and for durability and long life, should have a stronger gear train than the primary gearbox. That means the gears and shafts should be equal in strength to those in the transfercase. That would rule out using gears from any of the LT 77 /R380 77mm gearboxes unless as previously suggested, the layshafts were doubled up. While the 27% OD ratio of the Fairey unit suited my agricultural wide ratio Ford truck 4spd box quite nicely I believe something closer to 15% overdrive, or even 15% underdrive ratio would make for a better splitter box behind LandRover closer ratio transmissions. For a simple 2 shaft splitter I would consider using nothing less than LT95 gears, and it may be possible to mix and match individual LT95 main and laygears to come up with a ratio close to that number. From memory I think all the helix and pressure angles are identical.

[tacr2man]

Real shot in the dark question , would it be possible to bolt a splitter/o/d unit to the bottom pto position on the transfer box , as something in the fairy o/d type position seems to be very limited for space ?

[RangeyRover]

In the vapour spirit, wonder if a nuvinci hub will ever be strong enough for cvt offroad work.

Im sure bill that you will be interested in the techniques used to transfer torque in one of them.

[Snagger]

I can't see much difference mechanically between elliptical gearing sets and a multiple lay shaft system - you have lots of bearing sets and teeth meshes sapping a similar amount of energy and generating heat, and in both cases opposing planet gears or lay shafts cancel out tangental loads on the sun gear or main shaft. One is more compact than the other, but I don't see any reason one should be stronger or more efficient than the other because they are doing exactly the same thing.

As for Tanuki, I think I see the thrust of his point. The exact ratios he mentions are not hat point; what I see as the fundamental issue he raises is that the top gear selections should involve straight through drive, bypassing gear sets, so when the gear selection is giving you the least torque advantage by going high ratio, you are also minimising the gear set energy losses - it seems a shame to labour an engine with overdriving gear sets which are wasteful when straight though lock ups with higher ratio diffs would give the same end ratios far more efficiently. I hope that's what he was trying to illustrate - I don't want to put words in anyones' mouths. I think he's absolutely right - locking the gear box and a transfer box with a direct-locking 1:1 high ratio would mean the only gear sets to sap energy would be the diffs.

[Snagger]

Real shot in the dark question , would it be possible to bolt a splitter/o/d unit to the bottom pto position on the transfer box , as something in the fairy o/d type position seems to be very limited for space ?

You could, but it would be made more complex for it, also needing a new intermediate cluster as well as the main shaft gear (so that those two would no longer directly mesh) and complexity often means weaker.

[simonr]

I can't see much difference mechanically between elliptical gearing sets and a multiple lay shaft system - you have lots of bearing sets and teeth meshes sapping a similar amount of energy and generating heat, and in both cases opposing planet gears or lay shafts cancel out tangental loads on the sun gear or main shaft. One is more compact than the other, but I don't see any reason one should be stronger or more efficient than the other because they are doing exactly the same thing.

Mechanically, they do the same thing. Each gear to gear contact looses you a bit of efficiency. In a single stage planetary reduction, you generally have 3 (sometimes 2 or more) planet gears, a sun gear and a ring gear. Thus, the number of gear to gear contacts is 2 x the number of planet gears. Whereas with a lay shaft arrangement, you can achieve the same reduction with only one gear to gear contact. This is the primary reason for the efficiency difference.

The strength difference is for the same reason. For a given thickness of gear, you are trying to shear off three teeth for every one with a lay shaft. The Planetary box gives up to 3x the strength for the same thickness - one of the reasons they are popular in winches.

Si

[bill van snorkle]

I agree that the balancing forces within planetary gear sets are similar to those in twin or triple layshaft arrangements. But they do not seem to be as capable of dissipating the heat they generate quite as well. My only real world experience with planetary gears is with that in my crawler gearbox which is regularly used but usually only at speeds of 5mph or less. It has big beefy gears and large lubricant capacity, yet gets bloody hot, much hotter than the main box or transfercase when crawler range is selected. Planetaries even get hot at the low rpm application of reduction hubs. When Merc Benz were campaigning in truck racing, the planetary hubs would get hot enough to fry a steak on.

Fairey OD's also got much too hot, and rightly or otherwise I put that down to insufficient lubricant capacity and high tooth loadings from using relatively tiny undernourished gears. That it was always the higher ratio primary pair of gears in the OD that burnt out or broke, and not the output pair appeared to suggest that tooth loading was the cause of much of the heat.

Back on the subject of heat. A mate of mine of mine fitted a planetary geared winch to the rear of his Jeep mainly to allow him to repell down hills too steep to safely drive down. Whilst the winch was satisfactory for rearward self recovery, the first time he used it to lower the jeep down a steep slope the winch drum got hot enough to fry the plasma rope. He changed over to a Warn Hi mount which probably due to spur gearing stayed much cooler.

[Bowie69]

Did the winch have it's brake in the drum then?

[bill van snorkle]

Did the winch have it's brake in the drum then?

Good point.I don't know to be frank. I think he may have been just descending with the gearing. I'm more familiar with worm drive winches, where braking isn't required.

[ejparrott]

You could, but it would be made more complex for it, also needing a new intermediate cluster as well as the main shaft gear (so that those two would no longer directly mesh) and complexity often means weaker.

Does it? I was under the impression the transfer box was left alone, and you had a new gear which meshed with the existing intermediate cluster?

I've seen 3 of these on ebay in the last 4 years, all gone for far more money than I can afford. I'd really like one for the 88, as I don't want to loose my OD.

[bill van snorkle]

Does it? I was under the impression the transfer box was left alone, and you had a new gear which meshed with the existing intermediate cluster?

I've seen 3 of these on ebay in the last 4 years, all gone for far more money than I can afford. I'd really like one for the 88, as I don't want to loose my OD.

I think you are referring to a bottom PTO, not a splitter overdrive.

The earlier Fairey overdrives had a short splined section protruding from behind the rear upper bearing,which was intended for a PTO adaptor that Fairey originally promised would be available but never delivered, after conning a couple of hundred of us with PTO winches into buying their OD's on the strength of the promise.If you want a PTO badly enough and are willing to spend a few bob it can be done though. At some expense I adapted a shortened PTO to my overdrive, and transferred it over to my crawler box when I fitted that.

[Anderzander]

I'm sort of the other way - I'd rather like an underdrive but have a hydraulic pump fitted in the std PTO.

[bill van snorkle]

I'm sort of the other way - I'd rather like an underdrive but have a hydraulic pump fitted in the std PTO.

You can have anything you want on Vapour threads.

[ejparrott]

I think you are referring to a bottom PTO, not a splitter overdrive.

yup

[Nigelw]

You can have anything you want on Vapour threads.

That you can, but what I want to know is how we can convince you to stop sniffing the vapors and get into the workshop and knock something up

But I have been pondering this point you made Bill, why only 15% O/D opposed the 27% Fairey went with? Would it be to make the gear sets smaller diameter but wider ? Very curious of this?

[Snagger]

Mechanically, they do the same thing. Each gear to gear contact looses you a bit of efficiency. In a single stage planetary reduction, you generally have 3 (sometimes 2 or more) planet gears, a sun gear and a ring gear. Thus, the number of gear to gear contacts is 2 x the number of planet gears. Whereas with a lay shaft arrangement, you can achieve the same reduction with only one gear to gear contact. This is the primary reason for the efficiency difference.

The strength difference is for the same reason. For a given thickness of gear, you are trying to shear off three teeth for every one with a lay shaft. The Planetary box gives up to 3x the strength for the same thickness - one of the reasons they are popular in winches.

Si

I still see no advantage - an epicyclic gear set with three planet gears will have six meshes - planet with sun and planet with ring, times three. A three lay-shaft system will also have six meshes - the front end of each lay shaft to the outer concentric output shaft and the rear end of each lay shaft to the inner main shaft. The thing is that a multi-lay shaft will be turning more mass of metal, but the radius of each piece is less. The ratios of mass/radius of all the turning parts will influence the amount of energy lost in turning all those parts, but I'd expect the epicyclic system would be more efficient and reliable as well as more compact for a given weight/strength. That's why they're used for aircraft propulsion gear boxes on turbine powered aircraft.

[Snagger]

I agree that the balancing forces within planetary gear sets are similar to those in twin or triple layshaft arrangements. But they do not seem to be as capable of dissipating the heat they generate quite as well. My only real world experience with planetary gears is with that in my crawler gearbox which is regularly used but usually only at speeds of 5mph or less. It has big beefy gears and large lubricant capacity, yet gets bloody hot, much hotter than the main box or transfercase when crawler range is selected. Planetaries even get hot at the low rpm application of reduction hubs. When Merc Benz were campaigning in truck racing, the planetary hubs would get hot enough to fry a steak on.

Fairey OD's also got much too hot, and rightly or otherwise I put that down to insufficient lubricant capacity and high tooth loadings from using relatively tiny undernourished gears. That it was always the higher ratio primary pair of gears in the OD that burnt out or broke, and not the output pair appeared to suggest that tooth loading was the cause of much of the heat.

Back on the subject of heat. A mate of mine of mine fitted a planetary geared winch to the rear of his Jeep mainly to allow him to repell down hills too steep to safely drive down. Whilst the winch was satisfactory for rearward self recovery, the first time he used it to lower the jeep down a steep slope the winch drum got hot enough to fry the plasma rope. He changed over to a Warn Hi mount which probably due to spur gearing stayed much cooler.

I agree that it's the heat that is the problem on both types of unit, and that the bearings on the Fairey are pitifully small. Rather than coming up with a completely new design that achieves the same thing, creating a heat exchanger or oil cooler system would probably be more beneficial. Using the transfer box filler plug hole would be a good return line point, but then again tapping a line into the top of the case might be better so that the filler hole can still be used for level checking. The challenge would be in siting the hot oil outlet port. Maybe somewhere on the rhs of the transfer case would work? Cant't use the rear face because of the hand brake, or the front face because of the 4wd housing, and using the drain plug would be inviting disaster off road, getting ripped out on the first obstacle or in deep mud. But what about oil flow? What would work to pump the oil through the cooler? I don't know if an electric fuel pump would handle the heat and viscosity for long.

[Snagger]

Does it? I was under the impression the transfer box was left alone, and you had a new gear which meshed with the existing intermediate cluster?

I've seen 3 of these on ebay in the last 4 years, all gone for far more money than I can afford. I'd really like one for the 88, as I don't want to loose my OD.

My post probably was unclear. Using a bottom PTO configuration for an overdrive would require additional new input and intermediate gears to take those tow out of mesh, and would also be tight on space laterally as the OD input and output would have to be side by side, the drive line dropping down from the gear box main shaft to the OD input shaft and then to the right to its second shaft before being routed back up to the intermediate cluster. One of those shafts would need sliding members to lock and disengage the 1-1 and step up gears, and even in 1-1 you'd be running the torque through gear sets rather than locked shafts, so loosing efficiency. It'd be much more complex and less reliable and efficient than the existing designs that use the rear PTO position.

[bill van snorkle]

That you can, but what I want to know is how we can convince you to stop sniffing the vapors and get into the workshop and knock something up

But I have been pondering this point you made Bill, why only 15% O/D opposed the 27% Fairey went with? Would it be to make the gear sets smaller diameter but wider ? Very curious of this?

To be honest Nigel, my LandRover will likely not see much further development, as it contains all the features I regard as necessary for it to perform in the conditions it is most often used in. I much prefer the deep reduction crawler than an overdrive. I have been really feeling my age and more lately, so aside from the relatively easy job of making up another crawler for my LT95 equipped Rangerover I'm not likely to knock up anything or anyone anytime soon.

My Rangerover, with 0.996:1 high range gears is quite high geared enough, and many believe that the common 27% OD ratio is a bit tall for all but super smooth and flat motorway conditions, which I rarely travel on anyway.

I've calculated all the main gearbox ratios with a 27% ratio and a 15% ratio for the LT95. See which ratio you prefer, because being a vapour project, I am offering either option, lol.

27% OD split ratio. 15% OD split ratios

1st gear direct = 4.069:1 1st direct = 4.069:1

1st gear OD = 2.970:1 1st OD = 3.45:1

2nd gear direct = 2.448:1 2nd direct = 2.448 : 1

2nd gear OD = 1.80:1 2nd OD = 2.08 : 1

3rd gear direct = 1.505:1 3rd direct = 1.505 : 1

3rd gear OD = 1.10:1 3rd OD = 1.28 : 1

4th gear direct = 1: 1 4th direct = 1.00 :1

4th gear OD = 0.73:1 4th OD = 0.85:1

I prefer the 8 distinct and progressive ratios of the 15% split, but others may disagree, and it would also depend on the type of gearbox fitted as to what splitter ratio would be the best compromise.

[Snagger]

Just out of curiosity, Bill, how old are you? I'm only 40, and if it's any consolation, feel much how you describe already - I find it hard to drum up the enthusiasm to go into the garage to work on my RRC, but then I am continuously putting in the legal maximums at work (not my choice).

What tyres do you use on your RR? If they're oversize, then the vapourdrive would need to be a crawler for your use. Mine gets plenty of road use (or did), and very little off road, and even though it only has a standard 300Tdi turning the R380 and BW unit, I often wish for a six "cruising" gear on motorways. I might fit slightly oversize 235/75s when it's finished just because of that.

[bill van snorkle]

Just out of curiosity, Bill, how old are you? I'm only 40, and if it's any consolation, feel much how you describe already - I find it hard to drum up the enthusiasm to go into the garage to work on my RRC, but then I am continuously putting in the legal maximums at work (not my choice).

What tyres do you use on your RR? If they're oversize, then the vapourdrive would need to be a crawler for your use. Mine gets plenty of road use (or did), and very little off road, and even though it only has a standard 300Tdi turning the R380 and BW unit, I often wish for a six "cruising" gear on motorways. I might fit slightly oversize 235/75s when it's finished just because of that.

Hi Snagger. I am 64 years old, but although my brain is reasonably active and enthusiastic, what with quite advanced Rhumatoid Arthritus and living in the bush in one of the colder parts of OZ I'm finding it increasingly difficult to get out there in my unheated open air workshop to turn some ideas in to hard metal.

I originally got the RangeRover with a view to transferring my portal axles and transmission from my swb series over to it and have a single extreme capability vehicle that was also capable of covering long distances in relative comfort at respectable highway speeds. I have since realised that with the kind of capabilities the Rangey would then have,and the type of terrain I enjoy playing in, that I would not be able to keep the panelwork in reasonably straight roadworthy condition for more than 5 minutes.So I have abandoned that fantasy. I'm currently making up a pair of crawler boxes for a couple of mates, and as it doesn't require drastic modifications to the vehicle I thought I might as well hang one off the back of the LT95 as well, really for the hell of it. The Rangey is currently running only 31'' tyres, but with difflocks and any type of traction tyre, once crawler gears have been experienced I feel a little naked with low range in the 40's.

[Nigelw]

I am finding this very thought invoking due to having fitted 32" tyres over the 29" originals, (although there is a picture somewhere in my build thread showing the comparison of new tyres to old and it looks much more than a 3" difference) and while I am thinking great for giving it legs on the highway I actually found the low range to be a lot higher geared than I thought.

I think my own compromise would be in going outside the two choices of 1.2 or 1.4 and actually have a 1.6 and an over drive strong enough to cope with my driving.

My own thinking behind that is that I get a lot more control and slower speed when I need it and also get sensible high range gearing for towing or just bumpy tracks, but then I really would need an O/D and so far we have not yet found the greatest solution to this issue.

Now this being solely vapor I am not happy as it has given me far too much to think about, and not being an engineer or having anything more than a basic empty barn with a few primitive hand tools I and a welder I am fairly sure I can't knock anything up but in my head I am cruising the 314 in 4 O/D at 120kph barely hitting 2100rpm

[bill van snorkle]

I am finding this very thought invoking due to having fitted 32" tyres over the 29" originals, (although there is a picture somewhere in my build thread showing the comparison of new tyres to old and it looks much more than a 3" difference) and while I am thinking great for giving it legs on the highway I actually found the low range to be a lot higher geared than I thought.

I think my own compromise would be in going outside the two choices of 1.2 or 1.4 and actually have a 1.6 and an over drive strong enough to cope with my driving.

My own thinking behind that is that I get a lot more control and slower speed when I need it and also get sensible high range gearing for towing or just bumpy tracks, but then I really would need an O/D and so far we have not yet found the greatest solution to this issue.

Now this being solely vapor I am not happy as it has given me far too much to think about, and not being an engineer or having anything more than a basic empty barn with a few primitive hand tools I and a welder I am fairly sure I can't knock anything up but in my head I am cruising the 314 in 4 O/D at 120kph barely hitting 2100rpm

If one of the available standard LandRover transfercase gearing options gives the legs you desire Nigel, and you would like low range to be lower then a Maxidrive low range conversion, available from MR automotive in Queensland I believe should be a reasonable compromise

[Snagger]

I am finding this very thought invoking due to having fitted 32" tyres over the 29" originals, (although there is a picture somewhere in my build thread showing the comparison of new tyres to old and it looks much more than a 3" difference) and while I am thinking great for giving it legs on the highway I actually found the low range to be a lot higher geared than I thought.

I think my own compromise would be in going outside the two choices of 1.2 or 1.4 and actually have a 1.6 and an over drive strong enough to cope with my driving.

My own thinking behind that is that I get a lot more control and slower speed when I need it and also get sensible high range gearing for towing or just bumpy tracks, but then I really would need an O/D and so far we have not yet found the greatest solution to this issue.

Now this being solely vapor I am not happy as it has given me far too much to think about, and not being an engineer or having anything more than a basic empty barn with a few primitive hand tools I and a welder I am fairly sure I can't knock anything up but in my head I am cruising the 314 in 4 O/D at 120kph barely hitting 2100rpm

You'd be better off with the 1.4 transfer box, which will take an overdrive, and lower ratio diffs like 4.1 or even 4.74. Especially easy if your Disco is old enough to take a pair of diffs straight out of a SII/SIII (ie 10 spline diffs). The lower diffs will take some of the strain out of the gear box and od. They'd also reduce the ratio in low range as well as in high, which would help with the effects of the tyres.

[FridgeFreezer]

If you're compensating for big tyres IMHO the best point to do that is as near to the tyre as possible, so either hub reduction or lower ratio diffs, that way you correct high and low range at the same time.

As an example, I run 37's but my axles have an overall 5.99:1 ratio, which brings everything back down. I run a 1.003:1 LT230, which brings high range up to an acceptable level but low range is much lower than standard. This gives a nice low low-range and acceptable high range with no over/under drive.