Hydraulic Transmissions

[Deeja]

I'll start the ball rolling in the new category.

I have been asked by a fellow modeller whether these is a web site, or similar giving general information om the use of hydraulic transmissions in ride-on models [well 'live steam' is not really the right name]. He was asking about what has been used by others, how do you estimate/calculate the engine power required, anything to watch out for or avoid etc.

There seems to be a scarcity of info on this topic, and in Australia at least, although there are a few models, not all that many.

Appreciate any web links, or general inputs from those who have already done it.

Deeja

[bigt1677]

I dont have much experience in Locos with hydraulic drive and I think that you mean by HD, you refer to a fluid flywheel and mechanical transmission??

I have built a narrowboat that has hydraulic drive but this is pure hydraulic, i.e pump driven by diesel engine that supplies a low pressure high capacity circuit driving a motor via a reversing valve. Engine power is determined by working out how much power is required at the propeller then allow for 20 percent losses and that is the engine power required to drive the whole shooting match.

[chrisb]

A common solution is the Eaton 7 hydrostatic drive.

Belt drive input from i/c engine chain drive output to axles/countershaft. It does forward reverse and variable speed.

Have a look at this chap's website, he has made a 4 wheel ride-in loco. www.beevers.org.uk

Also I beieve some of the Mardyke commercially built locos have this set up driving one bogie of their sit in bigger diesel outline locos

[5inchrail]

I believe you need to contact Roger Greatrex at www.knightleylightrailway.co.uk/news.htm you will find an email address on his homepage. I'm sure he could provide some pointers.
Barry
www.5inchrail.com

[steam4ian]

G'day Deeja

The Morphett Vale 7.25' club started out with petrol powered locos using the fluid couplings out of washing machines. When you say Hydraulic Drive, is this what you mean? (I have kept our old washing machine so I can recover the coupling out of it.)

I have specified fluid couplings to drive pumps years ago. It wasn't too difficult to find the size even for an electrical engineer like me. One thing I did learn from an old timer is that the fluid level is critical and later had a need to prove that.

In smaller ratings you can also get centrifugal couplings and powder couplings. The latter work like fluid couplings except they use a granular material to connect the input drive to the driven output.

Regards
Ian

[ilvaporista]

The system seems very popular in the 'States, there is also a Yahoo discussion group which is very active and full of advice. I am away from my usual computer so I can not post the links I have saved there.

The usual set up seems to be a small IC engine (Honda etc) through an Eaton pump and then with drive motors on the power bogie. There are many GP40 style locos in 7.5" described on the web.

[Boulder Creek]

G'day all,

I am the fellow modeler in question that this topic was started on behalf of and I have just signed up with this forum.
I am considering using a hydraulic drive for my next loco. By "hydraulic" I mean, a hydraulic pump driving a hydraulic motor in each bogie of a Bo-Bo style loco. I have looked at the Eaton style of Hydrostatic transmissions and don't think that they are the type of unit that I am after. I need a setup capable of driving two hydraulic motors (one in each bogie) from a 22 Hp Vee twin engine driving a Hydraulic pump. I want to be able to remotely control this from a riding carriage behind the loco. (The loco will not be of the ride on/in style)
I have only built petrol electric style drive setups before with a petrol engine driving an alternator which in turn drives an electric traction motor and know very little about hydraulics. I am hoping to find out the best way to size pumps, motors, and valving for this particular application. I also want to be able to “free wheel” the loco when the engine is not running.
Any advice greatly appreciated.

Regards,
Dave.

[bigt1677]

first of all, a 22 hp engine will give you loads of power for any loco you build between 7 and 10 inch gauge. What you then need to do is match the pump and motors by figuring out what speed you want at the motor output spindle to run at, which of course is dependant on how your final drive to the bogie is set up and what ratio you require. Also consider how fast the prime mover will turn the pump, then its a case of matching and sourcing a set of motors and a pump to suit. Motors and pumps are matched by flowrate usually in litres per min in the case of a high capacity low pressure system. So figure out how fast the prime mover will spin the pump, work out how fast you want the motors to turn, then go to a hydraulics supplier and see what the closest match is. Freewheel can be achieved by simply fitting a bypass valve between the motor or pump inlet and outlet legs. Remember you will have to fit a cooler to cool the hydraulic oil, a filtration system, a direction control valve and a header tank.
Upside of hydraulic drive is flexibility and strength, downside is weight, bulk, expense and mess if you get a leak.
Hope this helps.
trev

[bigt1677]

PS

a correction - reading back through, just want to correct a small error. Flow is measured in cc per revolution both for motors and pumps - not in litres per min as stated. sorry.

[Deeja]

G'Day Boulder Creek,

Welcome to the forum

Deeja

[gilesengineer]

Hi, and welcome!

You may possibly find something in here of interest. when my brother built a diesel Hydraulic (not hydrostatic) Hymek in 10 1/4" gauge - and very successful it is too.

www.gilesfavell.seriouslyinternet.com/d7054.htm

It is generally reckoned that in our sizes it is difficult to get more than 6 or 7 HP actually down to the track, an our loco's don't have the weight to get more down. (scale loco's, that is)

All the best

Giles

[Boulder Creek]

Thanks to everyone for the advice so far.

The 22 hp engine was decided on so I could run it at not much more that idle speed as the Honda type 4 stroke engines sound terrible when running flat out. In reality the loco probably won't need any more than half of the available power from the engine. With 8 x 32mm plate wheels at 220mm in diameter and the buffer beams or headstock's at both ends measuring 310mm x 630mm in 40mm steel plate, I,m sure there will be plenty of weight to put the traction to good use!
Below is a picture of the proposed loco which is a 2 foot gauge E.M. Baldwin sugar cane loco which runs at the Isis mill in Queensland. As with my other locos, it will be built to a scale of 3.3:1 on 7 1/4" gauge.
I am looking into some hydraulic motors and a pump at the moment for this loco.

Regards,
Dave

[bigt1677]

Hi,
what sort of engine is the 22hp one?

Have you decided yet how you are going to set the drive ratios, i.e use the hydraulics to gear it down or use a final drive reduction or both - very interested to know how you get on with this and how you tackle it.
thanks
trev

[Boulder Creek]

G'day Trev,

The intended engine is a Honda V-twin or equivalent. I would like to get the hydraulic motors to drive at a ratio of about 1.5 : 1 and then gear them down a little to get the final speed correct. I am a little way off making a start on this loco yet but as with the current locos I'm building you will be able to follow the progress on my website at: www.smex.net.au/bouldercreek
As you will see in the "construction" page, I have done an article on how I have used an alternator to power the traction motor in my first loco. I may do an article on the hydraulic setup too once I have completed it.

Regards,
Dave.

[bigt1677]

Dave,
that is a fantastic setup you have over there. Good luck with the loco and drop us a quick line to let us know when you are going to start on it, then we can follow progress via the website.

cheers
Trev

[isc]

Saw a loverly 3 cylinder diesel in a large ride on mower,30hp driving hydralic motors on the wheels and the three cutters,it would proberbly take up less room than the Honda,but the sound is wrong--its too quiet.It runs much cooler than a petrol engine.Its liquid cooled so needs a small radiator.Just a thought,isc

[gilesengineer]

Bear in mind that you want to make sure that you match your maximum speed to the hydraulics working fully open (without flow being bypassed) as otherwise you get a large amount of your horsepower being absorbed as heat in your hydraulic fluid. (keeping the hydraulic fluid cool can become a significant issue).

My brother's Hymek has a single valve control, which is variable, forward and reverse, with a free-wheel spool integral. The free-wheel means that you can bring the lever/hydraulics back to idle at speed, and the loco will coast. Without this addition, the hydraulics would work in direct relation to the lever position (as it does with hydrostatic units) - which makes driving a bit tiring...

[Boulder Creek]

That sounds like a good setup Giles,

Can you tell me any more about the valve it self? Brand/part no.?

[steam4ian]

G'day Dave

I would have thought you closeness to Hobart and other boating places would have given you access to chandlers selling hydraulic winch drives for fishing boats etc. The logging industry also uses hydraulic gear for small drives in saw mills and the like so you should have plenty of product to chose from. Look up material handling equipment suppliers in your Yellow Pages

You live in a great part of Tasmania, come to think of it, there isn't much there that isn't great.

Regards
Ian

[Boulder Creek]

Thanks Ian,

Yes we do have chandlers and boat places who sell hydraulic winches. Unfortunately they know little about the winches they sell and even less about the hydraulics that drive them. I used to work for a company who made boat winches and even they weren't much help. A local hydraulic supplier was less than interested in my project and said if I could come up with a brand and part number then they could most likely supply what I was after? If I was just after a valve to make a hydraulic ram go up and down or a thingy on the tractor to turn one way or the other then no problem. A miniature loco.... hhmmm....not sure if we can help you with that one???

Regards,
Dave.