5 inch gauge petrol loco problems...

[ss25235]

Hi,

I'm building a 5 inch gauge model of NBL diesel shunter number D2767 (Based at the Boness and Kinniel Railway).I'm hoping to power it using a small petrol engine and I need some kind of transmission for it. Petrol electric would be far to expensive, petrol hydraulic would be to dificult and probably just as expensive, so that just leaves petrol mechanical but I've got no idea how to put it together. I'm thinking of using the "Seal" engine from Hemingway kits. Any help would be highly appreciated.

Thanks,
Calum.

[ilvaporista]

I seem to start all of my posts with.. It depends...

What is your objective? Is it to replicate the same sort of integrated gearbox that the prototype has? Or do you just want it to move with the minimum of parts and work? Or something in between?

If you make a Seal why not look at the 1831 design from Edgar Westbury for some ideas? This was serialised in ME around 1941/2 or so.

If the engine is mounted with the axis in line with the frames then you are going to need to turn the power by 90 degrees. The engine mounted transversally leads to easier solutions but watch out for the overall width. The Seal on 5” should pull one or two people. Are your expectations higher?

Some ideas based on past experiences of low cost solutions.
Bevel gears from hand drills are good for turning 90 degrees. Don't think about the cheap Chinese alloy models in the shops today. Go to a car boot sale and look for old ones which had machined gear sets. As they have a reduction they are great for reducing speed and increasing torque. Most IC engines run way too fast to connect direct to the wheels. These bevel gears run OK dry but either a drip oiler (depends on how fussy the track owner is...) or an enclosed gear box with grease will help prolong life. I made a shroud out of an old circular margerine tub with a nylon bush running on the axle, packed with grease it worked well until damage during a derailment broke it.

I have used all sorts of transmissions but found chains to be the simplest and cheapest. Bike chain and sprockets are very simple and quick to use, you will have to make up collars and bushes. The hardened sprockets can be drilled by leaving them in the fire overnight (or in a well stoked BBQ!). After you have drilled the holes heat them up again and then quench from red heat to bring back some of the hardness.

Car timing chains work well also but as I get mine very second hand they do tend to rattle a bit.

Toothed belts work as well but you will need to make or find the right sprockets. As these are OK in aluminium it’s not a great problem to make them and a great confidence booster on your way to cutting real gears. You will need a good tension to stop the belt from jumping.

Avoid ribbed timing belts as the tensions required really do eat in to the power output of the engine.

I have seen V belts used but have no experience of them.

Having an IC engine reverse is a big issue and I have used many strange and varied ways. With the bevel gear arrangement you can make a sliding shaft across the face of the gear with the two pinions fixed to it, so that when slid one way the first pinion engages on one side and when slid the other way the other pinion takes the drive. On that arrangement note that the bevel gear can not be on the main axle as the pinions need to be on the centre line of the driven shaft.

I also used as an experiment the tumbler reverse from an old lathe, noisy but functional. You need to have a positive locking method to stop the gears from jumping out of mesh.

I did use one of those 90 gearboxes for electric motors but these can not be back driven. That’s OK with a petrol engine and if you put it before the clutch you can still push the loco along when dead.

If you are close to the coast the best source of reverse gearboxes come from the larger outboard motors. Maybe E Bay could turn up a scrap motor for a good price. I have found these well up to the duty on a heavy passenger hauler.

With an IC engine you will need a clutch. After some experiments I gave up with plate clutches and went centrifugal. My home made experiments failed due to vibration and problems with friction materials. My clutches are from mopeds and are very easy to install. The old Honda 90 scooter has a very neat and separate clutch with drive for a reduction gear incorporated.

Being afflicted with a large family, large mortgage, busy job etc my solutions are less refined and more down to earth than most and many of my projects are putting together bits hoarded over the years.

I have an aversion to throwing mechanical devices away so over the years of mopeds, motorbikes, boats and now planes many parts now are stacked away for some future use.

I have to confess to an upbringing by parents with a similar outlook as anyone who has read my father’s Make do and Mend series in MEW will know.

[ilvaporista]

Not one that I made but I did see a strimmer motor connected to a car alternator as the basis for a 5" petrol electric. Each bogie had an electric motor and there were some clever electrics in the middle. It was quite a sight but the buzzing of the strimmer did not sound quite like the real thing. I shall try and find some photos of my creations to post, alas done before I had a digital camera. If nothing else you can see what not to do..

[isc]

Just used as a portable power supply, I have an old Villiers 2 stroke atached to a car alternator, this gives abouit 300 watts continuous(the motor over heats, and siezes when delivering higher wattages), a small fan for cooling would help a lot.
If nothing else, the wee 2 stroke makes plenty of smoke if thats any use. isc

[ss25235]

Thanks a lot for the help it's fantastic!

[Deeja]

Calum,

Petrol electric does not necessarily mean expnsive or complicated. Look at what Dave has done at the Boulder Creek Tramway at www.smex.net.au/Bouldercreek in the Construction section.

Deeja