Vapour overdrive project.

[bill van snorkle]

Personally, I have no interest in single gear overdrives. I'd rather use the PTO aperture for an underdrive or a proper full range splitter type overdrive, But yesterday while figuring out my next LT230 underdrive, it occurred to me that despite several attempts, British industry seem quite incapable of producing a long lasting, strong, quiet overdrive that is capable of being used in all gears as a splitter box ! Why is that ? Fairey and GKN decided it was better to cease production rather than exercise a bit of grey matter to address the weaknesses in their respective designs.

Due to the often excessive heat they generate in hotter climates,I'm not keen on planetary gearing (GKN) for high revolution work, but for Fairey, the solution was staring them in the face. They had all the mechanical components already made and sitting on the shelf.All they needed was to cast a new casing

See, in the heavy truck transmission industry,to make a strong gearbox, they don't necessarily need to make huge gears and shafts. They simply double up or even triple up. All Fairey needed to do was to make a new case that would allow 2 standard layshafts, which would have doubled the strength of the gear train and halved the tooth contact pressure to improve quietness.

The famous mainshaft to overdrive coupling spline wear issue was easily solved too.

For anyone contemplating buying up some Fairey OD bits and making their own twin layshaft OD, I say go ahead with confidence.

Being a Vapour build, I have already done it whilst typing this post. And like all my Vapour builds, it works perfectly well and is bullet proof.Lol

[o_teunico]

you are a genius Bill!

[bill van snorkle]

you are a genius Bill!

Smilies not working today O'teunico ? Lol.

[De Ranged]

Same principle as my vapour portal hubs, double up the lay shafts and gears... now if I can find 3 more hilux transfer cases lol I have a bit of a habit of gathering vapour parts

Arghh speaking of that.... just for the sake of us not so clued up bill how do we tell the different types of overdrives apart, just I have one now and I it looks like I maybe going for a drive to get another truck tomorrow that has one

[simonr]

I've not dismantled a LR Overdrive, but have one or two others. IMHO, the heating problem is due to the use of Planetary gearsets. A single gear to gear reduction is 6x as efficient as a planetary gearset with the same ratio.

Planetary reduction obviously lend themselves to the coaxial PTO drive arrangement - but at the expense of the heat generated. For a long lasting solution, ordinary spur gears, even helical gears are likely to give you what you want.

I have thought a bit about this, making a simple 3 speed box out of the helical gears from an ordinary manual gearbox. It is rather virtual at the moment as I moved on to considering building the whole gearbox & transfer box in one unit using a ball-clutch selector (like a motorcycle box) and 8 gears to cover 0.5 x Low 1st to 1.25 x High 5th. Then use two chain drives, selected by another ball clutch to select drive to the Front, Rear or both. The whole thing looked remarkably simple. Reverse being the biggest headache.

Si

N.B. I've made a couple of pretty good gearboxes by having the support plates for the shafts water-jet cut (which has plenty high enough tolerance), separating the plates with tubes. Bolting through the tubes and welding plates between the tubes to enclose the gears. Not great for production, but low cost enough for a one-off.

[bill van snorkle]

De Ranged, on 27 Sept 2013 - 08:49 AM, said:

Same principle as my vapour portal hubs, double up the lay shafts and gears... now if I can find 3 more hilux transfer cases lol I have a bit of a habit of gathering vapour parts

Arghh speaking of that.... just for the sake of us not so clued up bill how do we tell the different types of overdrives apart, just I have one now and I it looks like I maybe going for a drive to get another truck tomorrow that has one

Due to the high end thrust that helical gears generate,it wouldn't be a good idea to use Hilux transfercase gears in portal boxes. Even with relatively shallow helix angles the 404 Unimog portals occasionally blew their drop box castings apart, and the later Mogs went to spur gears.

It is highly likely that the overdrive you have and the one you may be getting are Fairey brand ones.

The Spanish Ribus or Toro brand versions were virtually identical internally but had a larger ribbed casing that held more lubricant. GKN planetary geared OD's AFAIK were never made for series t/cases.

The Canadian Rocky Mountain overdrives are also planetary geared and were made for series t/cases as well as LT230's, but it would be very rare to find one fitted to a series vehicle in OZ or NZ as they cost more than most series vehicles are worth.

Planetary overdrives are cylindrical in shape, whereas the 2 shaft Fairey and Toro/Ribus are irregular shaped.

[ejparrott]

Fairey Series OD's use a layshaft and helical cut gears, OD's for the LT230 use planetary gears. I've occasionally thought about new gears and shafts for a series OD to alter the ratio, but haven't had the need really.

[bill van snorkle]

I've not dismantled a LR Overdrive, but have one or two others.

If the 2 overdrives you have Simon are Laycock ones, they are virtually identical to the GKN versions for LandRover. GKN used Laycock planetaries in modified form to provide co axial, or is that concentric drive?

[Nigelw]

Possibly the need for over drives has been reduced greatly as modern new Land Rovers have a 6spd box, now getting your paws on one of them cookies might yield some more gears to play with Bill?

But I randomly wondered this a good while ago, why not make the transfer box 3 stage splits and synchro between mid and high? giving lots of options there to mix and match?

[bill van snorkle]

Possibly the need for over drives has been reduced greatly as modern new Land Rovers have a 6spd box, now getting your paws on one of them cookies might yield some more gears to play with Bill?

But I randomly wondered this a good while ago, why not make the transfer box 3 stage splits and synchro between mid and high? giving lots of options there to mix and match?

With the bellhousing cast as a unit with the gearbox Nigel, the 6 spd Puma trans does not lend itself all that easily to re adapting to other make engines. Besides, the only component of modern LandRovers I have any faith in is the LT230 t/case. Probably won't be long before they screw that pooch as well by using the LT230Q gears!

[Mr Ian]

Like an Atlas or Stak see Pirate for more details not a cheap fix. Just shaking the grey matter loose. Regards Ian Ashcroft

[bill van snorkle]

Like an Atlas or Stak see Pirate for more details not a cheap fix. Just shaking the grey matter loose. Regards Ian Ashcroft

I haven't read it with my own eyes Ian, But I believe that the makers of Atlas, Advance Adaptors consider a locked LT230 to be arguably stronger than their own baby. And probably more versatile too, what with the option of your driveline length friendly crawler box. Or a good overdrive, if someone would build one! Hint

[HPLP]

What are peoples experience with the bearmach overdrive? Ive heard of it but never seen one.

H

[Snagger]

The thought of a doubled or trippled Fairey OD had occurred to me too (never as a physical project as I lack the skills and equipment to do it), but I came to the conclusion that the weakness of the clutch sleeve would still be there and that the heat generated by trippling the number of meshing teeth and spinning bearings would probably be similar to that of the heat generated in epicyclic gears, so you'd lose the compact design with no benefits. The better solution would seem to be a compact epicyclic design in a large housing with high oil capacity, ideally with an induced oil flow through/over heat shedding areas. The cooling fins on the Roverdrive must help to some extent, but are not huge and it's oil capacity could be made much bigger as there is plenty of room to expand the casing without altering the innards. The way in which the Roverdrive shares its oil with the transfer box, using a finned bottom cover must also help, but a pumped oil cooler would be even better. Maybe an electric fuel pump with a length of coiled copper brake line would be effective?

Now, what would be a useful overdrive is one which would also function as an underdrive (ie, low, 1:1 and high) - I could really use that on my 109, giving huge flexibility for low speed and motorway work. I know someone was looking at it, but they shelved the idea because of the economy. Maybe if they considered how many more people could fit big tyres tot heir LRs, or cheap 3.54 diffs to Series vehicles but currently can't because they'd be overgeared, using the underdrive feature for town driving and accelerating and the high function like on current overdrives for long range cruising, so that people like me can have their cake and eat it, then there might be a market for such a unit.

[Tanuki]

Having spent quite a bit of time in the past fettling cars with the laycock-type overdrive [Volvos, Humbers, Triumphs, Reliant Scimitars, Jaguars, Bristols etc] I must confess to finding the whole idea to be flawed: basically overdrives were a crude way to overcome an insufficiently-high final-drive ratio and so get better cruising ability.

There's something instinctively right about the main gearbox having a 1:1 'straight through' top-gear with a dog-clutch that locks the input and output shafts together leaving the layshafts etc not turning at all.

This implies - to give relaxed cruising - a relatively high-ratio final drive [GKN-Salisbury kindly offered ratios like 3.22:1, 3.07:1 and 2.88:1 to accomodate this].

My "Ideal" 5-speed Land-Rover gearbox would have wide-spaced ratios: something like 4.1:1 3.45:1 2.7:1 1.8:1 and 1:1 [note the direct-drive 'top']

Then the transfer box would be 2:1 in low and 1:1 in high.

And 3.07:1 diffs. The idea being to gear it so maximum high-ratio speed was achieved in 4th 'on or beyond the rev-limiter' and 5th being very much a level-roads-with-no-headwinds-or-trailers overdrive/economy ratio.

Of course this would be a challenge to many UK drivers who'd have to overcome decades of ingrained "get it into top as soon as possible" driving-tuition [which only knocks-out big-ends, dual-mass flywheels and gearbox-bearings]. My approach is much more to let your engine rev freely through the gears even on a light throttle-opening: 60 in 3rd on half-throttle s nothing for a TD5 - there's a convenient rev-limiter to tell you when you really need to go for the next gear!

[o_teunico]

_{The Spanish Ribus}

I think that you are refering to RIBAS. I once had the handbook of one of those in my hands. It clearly said "can be used in any gear at any speed" and it aimed driver to use it as a splitter. Never heard about TORO ("BULL" in spanish).

The Santana parts catalogue shows both Fairey and Santana units. Quite surprisingly, the complete unit´s reference is the same for both: GLR120A.

Will post a scanned exploded view of the Santana unit.

[o_teunico]

[bill van snorkle]

Snagger, The reworked Fairey clutch sleeve,with rifle drilled input shaft and screw oil feed, that I adapted to my crawler box, show little to no sign of spline wear after ten years of hard service. So as I stated before, that problem is easily solved, especially during manufacture, where the standard mainshaft gear spacer could be integrated with the clutch sleeve thus allowing for longer coupling splines.

Re double opposed layshafts. The manufacturers of heavy duty truck transmissions such as Eaton, Spicer, Mack etc disagree that this arrangement offers no significant durability or efficiency advantages over planetary gearing, otherwise they would only make planetary gearboxes.

Re wear/heat on bearings etc, example... A gear on a mainshaft driving a gear on a single layshaft is subjected to side thrust loads from the 2 gears trying to push away from each other. This side thrust is transferred to the mainshaft and layshaft bearings, and in some examples, series main boxes being a prime one, causes both main and layshaft to flex and ultimately fatigue and break. Now by introducing a second opposing layshaft, the side thrust/gear pushing away loads acting on the mainshaft and its bearings are virtually eliminated. the side thrust loads etc acting against the layshaft and its bearings are halved because there are two of them. Less side loads, less gear tooth contact pressure equals less wear and tear on gears,shafts, bearings etc, and a quieter gearbox to boot.What's not to like?

Whilst Tanuki's opinions are valid at the vehicle design stage, they are not very practical for most of us who are stuck with what Mr LandRover has given us, and lack the skills or resources to make drastic alterations. A properly designed bolt on splitter overdrive would transform the overall performance of even gutless 2.25 litre petrol powered landrovers with a horsepower to weight ratio of 40 BHP per ton, in a similar way to how a 16 speed Road Ranger box gives outstanding performance to a double articulated Kenworth B double grossing 60 tons with just 600 BHP does.

O'teunico, The Ribas overdrive has proven no more capable of coping with regular split shifting all gears than the Fairey units, because it uses the same size under nourished componentry.Fairey originally advertised that their units could be used to split every gear too. But they dropped that claim after too many warranty complaints from 'split' overdrive casings.

The Rocky mountain planetary overdrives share the same lubricant supply as the transfercase and have an Archimedes screw type pump arrangement to keep the OD gears fed. But it would appear from a thread on AULRO forums a while back,that excessive heat generation has proven to be a concern for some owners here in OZ who operate over long distances in the warmer parts of the country.

Anyway, I really only started this thread in an attempt to spark a little more interest in this 'Modified Vehicle Builds and Special Projects Forum,' which tends to go very quiet at times.

[simonr]

If the 2 overdrives you have Simon are Laycock ones, they are virtually identical to the GKN versions for LandRover. GKN used

Spot on!

What about using Citroen 'Herringbone' gears - then the sideways forces are balanced!

Si

[simonr]

P.S. I think the way to make it is using a Ball Clutch (or Ball-Lock) arrangement:

Very compact, strong and simple to make. I even 3D printed one!

Si

[bill van snorkle]

Very interesting Simon. I've not ever had much to do with motor cycles, and never come across the ball clutch system before.

I remember dismantling an early series 1 gearbox years ago that had a herringbone primary pinion and laygear fitted to it from some old Rover 60 saloon I believe. Whilst that would cancel endthrust, side thrust with a single layshaft will still radially load up the bearings, and in the Rover example, flex bend lay and mainshafts.

Tanuki, Your LandRover fitted with your 'Ideal' transmission of 4:1 1st gear x 2:1 low range x 3.07:1 diffs wouldn't pull the skin off a rice pudding with an overall ratio of only around 24.5:1.

[Anderzander]

A 3 range transfer box would be an interesting proposition.

[simonr]

Whilst that would cancel endthrust, side thrust with a single layshaft will still radially load up the bearings, and in the Rover example, flex bend lay and mainshafts.

Unfortunately, that's a feature of any gear to gear contact. You have a trade off between low radial force with shallow pressure angle, putting the gear teeth in shear which leads to the gears being weak and a steep pressure angle, the teeth being in compression and greater strength but higher radial force. Involute gears are considered to be a good trade off under most circumstances.

Fortunately, most ball races are designed to support higher radial than axial loads - but you do have to make the shafts strong enough or provide enough support to stop them bending. Helical gears give you similar radial loads but add axial loading too - but with advantages in noise & backlash. Herringbone, IMHO gives the best solution at the expense of cost.

Like all mechanical things - it's a series of trade-offs & compromises.

The Sturmey-Archer bicycle gears use something similar to a ball-clutch too, in a planetary arrangement.

Si

[Nigelw]

A 3 range transfer box would be an interesting proposition.

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?

[Bowie69]

I don't know enough about ratios, but what about the Toyota 3-4 speed transfer boxes out there?

http://www.kinzers.com/don/landcruiser/tcase_tech/tcase_tech.pdf

Any good?

I would have thought the options out there for diff ratios would get you closer to having a gearbox with ratios that would work, no?