reducing wheel slip in 5″ loco

[HobbsParticipant @edwardhobbs3]

Hallo all,

Last year I acquired a 5″ gauge “”hymek”” powered by an old 3 speed nsu quickly engine, I rebuilt the engine over the summer and it’s been running well since, happily pulling passengers for a full public running day with no issues.

It does however have one problem – it has more power than it knows what to do with! I added a large lump of lead above the driven truck (not sure on weight, possibly 15-20kg) and it’s helped a little, but it’ll still slip in all gears especially with two fully loaded cars behind.

Only the rear truck is driven, and there’s not really much more space for adding ballast there. There’s space at the front, but i suspect that would only serve to lift the rear end and reduce traction further.

I’d like to try reduce this issue if possible, but I’m not sure how to go about it. My initial thought was I needed to reduce the gearing (ie slow it down) but I think that’s backwards and I should actually increase the gearing (ie make it faster) so that it has less power to overcome friction. I did also consider rubber tires or similar for the driven truck to increase friction, but I suspect they wouldn’t last very long.

Any suggestions would be greatly appreciated

[noel shelleyParticipant @noelshelley55608]

Clean the wheels of ALL oils or anything that might lubricate ! Add more weight, 20Kg isn’t much  or turn it into a REAL hymec and power more wheels. Your engine/gearbox unit will not weigh much, a good electric may have 80Kg of batteries. Noel.

[BazyleParticipant @bazyle]

Add some brakes to the wheels. Yes they may wear quickly.

I assume it has a centrifugal clutch and you rev it up and suddenly it catches and dumps the power into the drivetrain. You could look at degrading the clutch grip or making it manual.

[Nigel Graham 2Participant @nigelgraham2]

Changing the speed by changing the gear ratio does not change the power for a given throttle setting, but it will change the torque at the wheels.

Rubber tyres won’t last long at all and may give other problems not readily predictable.

As Bazyle says, modify the clutch so it can be engaged more steadily, but don’t “degrade” it. You don’t want it slipping!

[duncan webster 1Participant @duncanwebster1]

Looking at the interweb, it looks like a normal motorcycle clutch. The early engines were 1.6 bhp, later high compression were more. This is quite a lot for a 5″g loco, especially as it has not a lot of adhesive weight. How about a driving truck which puts say half the drivers weight on the rear bogie of the loco. Don’t ask me how, I just come up with the daft ideas

[HopperParticipant @hopper]

You could put a big thick head gasket in the engine , or a stack of standard head gaskets, to reduce the power output.

Are you certain it is wheel slip and not clutch slip? Using modern automotive engine oils in motorcycle transmissions, primary drives and clutches can lead to clutch slip due to the friction modifiers in the oil. Automatic transmission fluid works well in that application, or specific motorcycle oil that is designed for clutches.

Using the gearbox in conjunction with overall gearing to keep the engine running in the middle of its powerband might help too. Too low gear will encourage wheelspin at take-off. Too high gearing can encourage wheel spin if the engine is lugging along at low rpm instead of motoring along happily at a midrange rpm. Its like driving a car on an icy road. Midrange rpm and careful throttle control are the secret.

Roughing up the wheel rims with emery paper? Cleaning them with brake cleaner to get every skerrick of oil off them? Making sure the ancient NSU engine is not dribbling oil onto the undercarriage during use?

[noel shelleyParticipant @noelshelley55608]

Hey Hopper, what do you know about driving on ice – may be a bit like outback roads though ? Noel.

[Dave HalfordParticipant @davehalford22513]

Hobbs,

Is the throttle a bit on/off, increasing the travel can give more control.

[noel shelley]

On noel shelley Said:

Hey Hopper, what do you know about driving on ice – may be a bit like outback roads though ? Noel.

I knew someone would say that!

Ah, but I lived for almost a decade in Montana, USA, a stone’s throw from the Canadian border high in the Rocky Mountains. Drove on solid ice roads for more than half the year most years, in temps down to 40 below. They don’t salt the roads there and only occasionally sand the main drags. So you learn to skate on all four wheels pretty quickly!

I only once put the car in the ditch, turning into our own driveway early on in the first winter and made the mistake of braking while turning. Only did it once! Got the car out of the ditch by running it in reverse while pushing it from the front. Then when it got traction and took off I had to run fast enough — on the ice — to get around the open driver’s door and jump in to take control. I sometimes wonder how I made to old age.

[noel shelleyParticipant @noelshelley55608]

At least you Know I’m paying attention Hopper ! Gentle slope down, sheet ice, 2nd gear, took foot off throttle and became a passenger in my own car – another lesson learnt ! I once taking the P out of a JW trying to SAVE me, said that due to dads work he had got me trade discount on a nice seat up in the Good Place ! As time has past I’m of the opinion may be someone is watching over me, it’s the only way I could have survived this long !  Noel.

[HopperParticipant @hopper]

Yep common occurrence on ice. Not unusual to be driving along and all of a sudden, zip!, and you are in the next lane, the tyres (tires in the US) having picked up on a ridge in the ice. Most of the time you were still facing the direction of travel, but not always. Luckily traffic speed was only 20mph or less . And we used to take our motorbikes out for a ride on it every New Years Day to a bar about 10 miles out of town. Yes, must have been someone watching over us. Or as they say, God looks after drunks and fools — so we had double indemnity.

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