auto gearboxes in boats like a DUKW or stolly?

[tankmaniac]

G'day.

Have a convo with some americans on aother forum about the possibility of using an engine and transmission from a car in a boat.

My questions was... Is it possible to have a smooth enough gearchange and utilise lower revs in the engine to cruise?

Some responses came back, pointing out that the reason boat engines run/rev quite high is that they are generally in '1st gear' all the time due to the enormous friction and pressure of the water against the hull.

 

Some suggested trying it.

This got me thinking... What does the DUKW and the stolly do to transmit power to the props or jets when in the water?

they are both manual or does the stolly have an auto?

 

Do they just stay in one gear when self propelling in water then?

What is the ride like?

Any ideas?

ta

matt

[antarmike]

Boat gearboxes are normally just forward and reverse. It is not uncommon to have a 1:1 gearbox/ forward and reverse gearbox . The marine gearbox is therefore should not be thought of as being in first, but in top, if you compare it to a car transmission where top gear is direct 1:1 through the gearbox. (although an overdrive fifth is of course top gear in some automobile gearboxes in which case 4th is usually direct.)

 

The forward reverse gearbox is sometimes followed by either a 2:1 or a 3:1 reduction box on the back, but this is a permanent, non selectable reduction.

 

The other point about using a car transmission, is often the thrust from the propellor is taken directly on the gearbox (or reduction gearbox). The Prop shaft rotates in the stern tube/stuffing box arrangement, and is free to slide back and forth in the stern tube. There may be couplings in the propshaft between the stern tube and the gearbox, and there may be a bearing or two to support the shaft, but often these are plain journal bearings incapable of taking thrust. The propellor therefore push the boat along, (or pulls it to a stop) by pushing and pulling directly on the thrust race in the back of the gearbox/ reduction gearbox. The thrust is transmitted to the boat, via the engine/ gearbox mounts.

 

A car tramsmission cannot be used in this way. it simply has no way of dealing with the propulsion forces acting directly on the output shaft on the gearbox.

 

And reverse gear, in a car gearbox, being a deep reduction would not swing the propellor fast enough to do any good.

 

A word of advice, Don't waste time on this experiment...

Edited September 30, 2009 by antarmike

[antarmike]

As you hint, by mentioning Jets, the Stolly was not driven by a propellor, it used water jets for propulsion. the two jets giving a total thrust of 2200 lbf, and steering was by way of hinged cowls at the end of the propulsion tubes, to deflect the water..

 

The Dowty marine jets are driven by PTO from the gearbox. The jets run in one direction only. To go backwards the ducts/ vanes are rotated 180 degrees to direct the water jet in the opposite direction.

 

There is no gearbox as such in the Stalwart /Dowty jet system, just a PTO from the main box.

Edited September 29, 2009 by antarmike

[antarmike]

Mods, Should this post be in the Naval section??

[ArtistsRifles]

As AM says - the Stalwart uses Dowty water impellers driven from a PTO - the throttle in the cab is fitted with a hand control to aid in keeping the RPMs where they should be and not exceeding the max limit. From memory about 2,500 rpm but would have to check the doc's or the rev counter in the cab to verify. Steering is done by clam shells over the Dowty outlets which can be moved fully back to give reverse propulsion.

It is also driven in water by the road wheels and steered as on the road by turning the wheel. Hence the steering ram position indicator in the cab floor.

The manuals give a max speed in water of 6 knots using both Dowty jets and wheels, 4 knots on the Dowty's alone and 2 knots on the road wheels alone.

Need less to say- the conventional gearbox is used to drive the road wheels and this is a 5 speed manual box. Not an auto.

[antarmike]

And the DUKW had a propellor, and steered by a rudder mounted behind it, but the front wheels were also used to help steer in the water.

[paulob1]

I dont think its 2500 neil, she wouldnt go at all...think its closer to 3500 but cant remember myself...at least with the stolly you have two modes of propulsion even if it is from the same engine...nd you can steer using just the wheels, so I am told as I have never had the nerve to take mine swimming just yet...would love to but just never got up the courage...

 

but with only 240bhp and pushing 10 tons with most of that below the water line, 6 knots isnt bad at all...

[antarmike]

A Motor narrowboat, used to weigh about 17 tons, its Butty boat about 10, and typically carried 50 tons between them. My Old boat "Bilster" had a 20 BHP Petter PD2 diesel and managed 4 MPH with ease. loaded and towing my brothers loaded Butty "Angel" (the speed limit on BWB Canals, but could do 6 MPH if you let it)

 

I find 6 MPH from 240 BHP in a Stalwart pretty pathetic......

 

And as Euclid demonstrated so well, the amount of water displaced is equal to the weight of the Boat, or swimmer. A pair of working Narrowboats is therefor displaces 7 or 8 times the amount of water, but can still do 6 MPH out of 20 BHP.

 

This is because it has low frictional losses in its gearbox, amd a relatively efficient propellor, Compared to the Dowty units. Eureka.....

Edited September 30, 2009 by antarmike

[Adrian Barrell]

This is because it has low frictional losses in its gearbox, amd a relatively efficient propellor, Compared to the Dowty units. Eureka.....

 

And a rather better hull design for the water, what with a lack of wheels and suspension componants to drag along!

[Gordon_M]

The DUKW sits in 2nd or 3rd gear plus marine drive and churns away till it gets there on the hand throttle. You can move it in the water by churning the wheels, but that's only in an emergency if the prop is fouled. Of course the front wheels change direction naturally with the rudder and help steering.

 

A DUKW transmission is fairly carefully matched to the work it has to do, replacing a DUKW engine with a big diesel will just chew up the transfer case, pillow block, rear diffs, or all three. In fact we once did a speed test on water with a standard DUKW matched against a German one that had been re-engined with a BMW 2 litre unit (to save money - road tax based on engine size in Germany at that time apparently) The BMW version kept up with the GMC motor no trouble at all.

 

When coming out of the water you also need to use loads of revs on a DUKW, so it pays to have your governor in good order and just hold the loud pedal down. I have seen DUKWS with big slow-revving diesels that wouldn't climb out properly, and standard DUKWS with 20" wheels and tyres for extra road speed that couldn't do it either because of the extra gearing effect.

 

As a Dodge person, I'd have to admit that the GMC 270 is my favourite engine - if I could stick one in a Dodge I'd give it a try.

 

Gordon

[antarmike]

And a rather better hull design for the water, what with a lack of wheels and suspension componants to drag along!

 

And without the top half of the wheels trying to push the Stolly backwards, whilst the bottom half is trying to push it forward! At least the Buffalo, driven by its cleated tracks in water, had only the bottom half of the track, moving backwards relative to the hull, in the water, and that portion of the track that was moving forward, relative to the hull was above water. A fully submerged wheel rotating in water is trying to push nearly as hard on the top half, as the bottom half is pushing the other way.

 

Though to be fair when commenting on hull design, a pair of Narrowboats fairly well fills the navigable channel on Britains poorly maintained and badly dredged canals, meaning the water being displaced at the front of the pair of boats, has a difficult job to get to the back of the boats to fill the hole the boat is laeaving behins it. Especially with all the weed to stop the flow.

 

Stalwarts, generally are used to cross fair sized rivers, where water is relatively deep, and water can easily get from the front to the back, as the Stolly moves forwards.

 

It has always been my opinion that the Stollies swimming speed was nothing to be proud of, and a better job should have been made of the swimming project....

Edited September 30, 2009 by antarmike

[Grasshopper]

The DUKWs on the london sightseeing tours have a turbo diesel fitted with an auto box. The gear lever states "use first gear in water only". Sounds to me like they have a cummins B series engine fiitted, which would easily couple to an Alison auto box.

[antarmike]

And when it comes to Stolly design, don't even mention putting the Petrol engine, under the load deck, of a vehicle that was often used to carry palleted jerrycans or Bulk Fuel equipment.

 

Road tankers and Aircraft refuelers always had a fire proof bulkhead between the engine in the cab, and the fuel they were carrying, in a tank behind.

 

The consequences of an engine fire in a stolly don't bear thinking about.....

 

Who thought of that one!

Edited September 30, 2009 by antarmike

[paulob1]

it was mostly and afterthought with the fuel supply, they had all the stollies then helicopters came ion and resupply was not needed by road, well not for munitions rtheir main task, this left I think 900 stollies with nothing to do so some clever spark dreamt up using them for fuel supply, get it spark...hehehe...

 

still great trucks even if it could and should have been done a bit better even in those days...

[antarmike]

it was mostly and afterthought with the fuel supply, they had all the stollies then helicopters came in and resupply was not needed by road, well not for munitions their main task, this left I think 900 stollies with nothing to do so some clever spark dreamt up using them for fuel supply, get it spark...hehehe...

 

still great trucks even if it could and should have been done a bit better even in those days...

 

Sticking a Petrol engine under the load deck of a vehicle designed to carry ammunition seems equally daft to sticking it under a Bulk Fuel tank....

 

RE the speed in water, DUKW could do 6.3 MPH in water in 1942, but the 1966 Stalwart is down to only 6 MPH, and that is progress?

Edited October 1, 2009 by antarmike

[ArtistsRifles]

Sticking a Petrol engine under the load deck of a vehicle designed to carry ammunition seems equally daft to sticking it under a Bulk Fuel tank....

 

RE the speed in water, DUKW could do 6.3 MPH in water in 1942, but the 1958 Stalwart is down to only 6 MPH, and that is progress?

 

Given the design brief to fit everything into a given size - that being the one defined by the common lower hull of the FV-6xx series -where would YOU have put the engine then??

 

As Paul says - the original design intent did not include the carriage of bulk packed fuel or UBRE systems, rather palletized loads of food, munitions, spares etc. to keep an armoured unit running.

 

Re. the relative water speeds - the Stalwart has a bloody great flat front end for the water to push against, no form of stream-lining at all, all the suspension, steering and drive components project out from the hull also adding to the drag -a DUKW has all this inside the outer hull and a narrow boat has that nice sharp front end to divide the water flow.

 

Oh and add to the above the fact the DUKW only weighed 7.5 tons and had a 2.5 ton payload - a Stalwart tips the scales at 9 tons and has a 5 ton payload. Aquatic speeds are quoted for laden so considering the fact the Stalwart is less streamlined (just) than a DUKW and is pushing another 4 tons through the water the 0.3 mph difference in speed isn't as bad as it's painted.

[antarmike]

Sticking a Petrol engine under the load deck of a vehicle designed to carry ammunition seems equally daft to sticking it under a Bulk Fuel tank....

 

RE the speed in water, DUKW could do 6.3 MPH in water in 1942, but the 1958 Stalwart is down to only 6 MPH, and that is progress?

 

My mistake 1058/59 for the Mk1, The Mk2 didn't enter production until 1966, so it was 24 years younger than the DUKW and slower.....

[antarmike]

Given the design brief to fit everything into a given size - that being the one defined by the common lower hull of the FV-6xx series -where would YOU have put the engine then??

 

 

If I had to put the engine under the load deck, I think it would have been an intrinsically safer diesel...

 

but the problem I would have had a go at it I had to use the same basic hull and transmission as the Salamander/ saracen/Saladin, would have been the propulsion...Ditch the ineffecient Dowty units ans use a proper propellor.

 

Heck... you can beat that speed with paddle wheels and a steam engine!

Edited October 1, 2009 by antarmike

[paulob1]

I think people are missing the point, when it was in the water it was intended to be secure away from enemy lines and not under fire, it didnt really need speed, can you see a dukw going landwise where a stlawart can go...give me any vehicle that can swim take a 5 tons load, unload itself if it has a crane and go virtually anywhere.including in water, on land...the only other solution was a helicopter and they won...not the dukw..the stalwart is unique and even today nothing can do what it can...so they got something right...agree a diesel in todays world would have been better but the b series engien was in everything in the 50's/60's easy to knock it now but then, it was the only choice...

Edited October 1, 2009 by paulob1

[ArtistsRifles]

It is worth bearing in mind the Mk3 would have had the same multi-fuel lump as the 432 Mk2 got - the K60 I think?? Sadly, as Paul says, the Stolly lost the battle to the Helicopter. A mistake I always thought as you can't shoot a Stolly down or have it grounded 'cos some jerk bought the wrong avionics system and you can't refuel other vehicles from a helicopter in woodland... Other planned changes for the Mk3 included selectable drive to cure the problem of transmission wind up on hard surfaces such as roads, improves rear vision for the driver.crew

 

Also - the Stalwart is the ONLY wheeled vehicle to earn and keep the title of HMLC (High Mobility Load Carrier) - have you ever seen a DUKW doing 40 mph across rough country???

Whatever their design shortcomings were - and yes, there are a few of them - a Stalwart did a job nothing else could have done then - and few if any can do since! It was designed to take a 5 ton payload anywhere an armoured unit could go, as well as one or two where they could not, at speed, using the closest the Army could get to standardised parts - hence the B series engine.

 

As an aside and off-topic, if you look - I think - on the "Britain's Small Wars" web site - there is a story there of them being taken out to Aden to replace RL's on convoys as the 0.5" balls from the tribes men's muzzle loaders went through RL cabs like a knife through hot butter but bounced off the thick steel and glass of a Stalwart.. Not bad for a vehicle classed as unarmoured.......

[Stormin]

I think people are missing the point, when it was in the water it was intended to be secure away from enemy lines and not under fire, it didnt really need speed,

 

Can't see 6mph being of much use in many rivers, it's not going to beat the speed of flow and lead to the vehicle being effectively swept down stream.

Only really usefull in still water and then it's usually easier to drive round than go across.

 

It's always going to be a compromise between land and water capability of dual purpose vehicles given the differing requirements.

 

Anyone know the rated speed of the CVRT in water? I believe this series of vehicles were also designed as a swimmers.

[Grasshopper]

A prototype Scorpion CVRT was fitted with propellors driven from the front sprockets. One problem was that it went fast enough to collapse the bow screen (which then had to be re-inforced with a metal plate) and another problem was there was nowhere on board to store such large devices!

[ArtistsRifles]

Can't see 6mph being of much use in many rivers, it's not going to beat the speed of flow and lead to the vehicle being effectively swept down stream.

Only really usefull in still water and then it's usually easier to drive round than go across.

 

It's always going to be a compromise between land and water capability of dual purpose vehicles given the differing requirements.

 

Anyone know the rated speed of the CVRT in water? I believe this series of vehicles were also designed as a swimmers.

 

FWIW - the OT is amphibious and it's water speed is supposed to be 15 KPH - or about 10 mph

 

And rechecking the data - the Stollys speed is quoted in Knots, not mph. Doing a Google conversion turns 6 knots into 7 mph....

[antarmike]

I think people are missing the point, .......can you see a dukw going landwise where a stlawart can go...give me any vehicle that can swim take a 5 tons load, unload itself if it has a crane and go virtually anywhere.including in water, on land...the only other solution was a helicopter and they won...not the dukw..the stalwart is unique and even today nothing can do what it can...so they got something right...agree a diesel in todays world would have been better but the b series engien was in everything in the 50's/60's easy to knock it now but then, it was the only choice...

 

When comments are made such as the stollie was designed to carry ammunition, or that it was designed to cross water in secured areas, not under enemy fire, therefor its speed in water is not important, We are not to loose sight of the fact that the Stalwart was not, initially, a military vehicle.

 

Alvis started the project as a civilian load carrier, for offroad use, oilfield exploration and the like. Like so many vehicles, including the Antar, it was the MOD who spotted an existing civilian design, and thought, "that could be useful to us"

 

The Mk1 Army Stalwart differed little from the earlier civilian model, and it was not until the Mk2 that serious thought was directed to the vehicles shortcomings, and design changes put in place to make it more capable in the water.

 

Re your comment, about unloading one-self with the crane, one consequence of the design with the engine under the load bed, is that if your engine fails, even for something bl00dy silly and simple which might be a five minute job in a conventional designed vehicle, even though many Stalwarts had a hydraulic self loading crane, you could not get to the engine to fix it without, unloading the load, and with an engine that won't run, the Hydraulic loader is of no help!

 

As I say Brilliant design work!!

 

The problem with the Stollie as a military vehicle is that is an adapted civilian design, and that means there is a lot wrong with it when you concider its military roles. HMLC should have been designed from scratch and then the result might be something to be proud of...but sorry despite trying to persuade me, I still think they are unimpressive....

Edited October 1, 2009 by antarmike

[Stormin]

Mike,

 

Are you sure the Stolly was originally concieved as a civilian load carrier? I am not aware of any with first users other than the military.

I can believe that it may as an after thought been seen as useful to oil pipeline companies etc. but how many were sold on this basis?

The majority of the underpinnings are the same as the military Saracen / Salamander from which it is derived. Even the engine (Rolls Royce B81), I believe to only have been used in military vehicles.

Surely if originally concieved for civilian use it would've originally had a diesel engine as most heavy trucks by that time.

When the military did get hold of the design it can't have been much further than the drawing board stage, were they could exert their influence as to engine type amongst other things.