Belt and Pulley Drives

[Atso]

Hi,

 

I was wondering if anyone had any experience using a belt and pulley transmission for a model loco. I've seen that Nigel Lawton sells components for these drives and also that some EM gauge members use them. I'm looking to build an N gauge 0-6-0 (J50) chassis with a quiet and reliable drive and would welcome suggestions.

 

Many thanks

[bertiedog]

Very viable as long as the smallest possible motor is used. There is a selection of pulleys, which would allow a lay shaft with the worm on it passing under the motor to allow a worm over the middle wheel.

 

Nigel Lawton supply small worm gears as does Ultrascale. It needs some planning to get the right belt and pulley, and Nigel Lawton has a calculator on his site.

 

Where the length of belt cannot be exactly matched a small jockey wheel can be added to take up slack.

 

With some smaller locos the very smallest motors are the vibrator types, and they are so small the lay shaft can be arranged as a stub on the end, with the worm outboard, driving an outer axle, rather than trying to reach the middle axle.

 

Use as big a motor as the space will allow, in 2mm and N gauge they have to occupy the cab etc , to be practical in smaller locos, with tender locos it is still the best way to place he motor in the tender, with a drive shaft to the main chassis, allows the boiler to be solid and weighty. The motor in the tender drives a layshaft under it, allowing the lowest position for the shaft , so that it is hidden as the drawbar. 2:1 belts in the tender will double the worm ratio, 3:1 might be possible in a small tank loco, with 15:1 worms, so 45 to 1 overall.

 

Stephen.

[hollywoodfoundry]

You also need to know that a belt drive on its own cannot achieve enough reduction for practical applications. Most drives are a combination of worm drive and belt drive to get a useful drive ratio. You could use a large number of shafts, pulleys and belts, but because the largest reduction is probably about 3 to 1, the complexity rises, and with it the potential for things to go wrong.

 

It is also important to get the right belt tension, too much and the bearing used on the shaft will wear out quickly, too little and you get slippage. I mostly use tiny ball races to support shafts to alleviate this problem. And you must make sure the pulleys line up underneath each other, because the most common fault with belt drives is the belt coming off, not wear.

 

Finally, belt drives can take up more space than gear drives, so they may not be practical in an N gauge situation.

[davknigh]

Steve,

 

You can find some info on belt drives and micromotors here; http://www.clag.org.uk/

 

HTH

 

David

[Pacific231G]

Jouef (the original French company) used to be very fond of using these on their mass market locos. I think the results were somewhat mixed though I have a couple of locos fitted with them. I'll ask a few people in the SNCFS what the pros and cons were between those and gear trains.

[Atso]

Thanks for the input guy!

 

My thoughts are to use a 6mm diameter micro motor mounted sideways on the chassis and use a 2 or 3 stage reduction to drive the wheels. This is a little bit on an experiment for me to see if this is viable for an n gauge loco.

 

Bertiedog thanks for the explanation, I've not been able to make a successful n gauge chassis yet some I might well be asking you for more advice in the near future! B)

 

Hollywood, what drives have you built using the belt and pulley system, I'm a fequent visitor to your site but don't remember seeing such a unit before (I'm going to double check now though!).

 

David, I'd seen the Clag website and this has been my inspiration for trying a gearless loco. Some really great stuff on the page isn't there! Seeing how two 6mm motors have been mounted on the bogie driving the wheels directly from the belts is really something else.

 

Pacific231G if you could find out how well the Jouef locos ran I would be most appreciative!

[bertiedog]

Don't compare the Jouef belt drives, or any other commercial ones, with the Nigel Lawton belts, which are far more advanced modern belt materials in Urethane rubber. Older drives used rubber or other materials that deteriorated with age etc, and do give troubles.

 

Being a smaller cross section diameter they put less strain on the bearings, as less tightness is needed compare to older rubber belts.

 

The big problem with N gauge and 2mm is the driving wheels, virtually the only suppliers are the 2mm association, or using commercial wheels from RTR models. If a RTR is scrapped it may provide the base for the motor and gears anyway, by re-arranging the parts.

 

Stephen.

[Miss Prism]

Nigel Lawton belt reductions can be in the order of 5:1, so in theory a 3-stage might get somewhere near what you want, but as hollywoodfoundry points out, this can get a bit silly space-wise compared to a drive using a worm on the final stage, and in practice, multi-belt reductions will have considerable friction in their shaft bearings unless counterbalanced or running in ballrace bearings, so become counterproductive in terms of the motor developing sufficient power at low revs. The 6mm diameter motors are understandably very sensitive to load, and can rev up to 35k off load, so the choice of overall gear reduction is important.

[hollywoodfoundry]

Hollywood, what drives have you built using the belt and pulley system, I'm a fequent visitor to your site but don't remember seeing such a unit before (I'm going to double check now though!).

 

All the BullAnts are available with belt-drive or gear drive now as an option, you will also see the In-Line drives used for diesel chassis, these are also available in belt or gear drive. And I have a new product for tram modellers that uses belt drive.

 

Since I began using these belts, I have changed to a larger cross-section belt, 1.0 x 1.0mm square, whereas the originals are 0.6 x 0.6mm square. Nigel's belts are also the smaller cross-section, so would be suited to small size applications such as N gauge. For HO or OO use, a larger cross-section belt with a correspondingly larger V section pulley is a better solution.

 

As Bertiedog says, the Jouef and Athearn drives used common rubber bands, and were quite troublesome. The belts used by Nigel and myself come from a company that makes drive belts for precision mechanisms and uses Chloroprene material. There are also precise cross-sections unlike normal rubber bands.

 

So far, experience has shown the belts do not wear appreciably, the only method of failure so far is the band coming off and being lost.

[jwealleans]

Steve,

 

Have a look at my WB thread and the Sentinel shunter I built earlier in the year. It's here on RMWeb or on the LNER forum as well. Very quiet and very powerful and I have plans to use some more.

[Atso]

Jonathan,

 

Thats great! Just what I was looking for. Glad that this is working out for you, I've just got some drive components from Mr Lawton today so on with designing the chassis - should be a good job for my CNC Engraving machine once I've got it up and running!

 

Steve,

 

Have a look at my WB thread and the Sentinel shunter I built earlier in the year. It's here on RMWeb or on the LNER forum as well. Very quiet and very powerful and I have plans to use some more.

 

Hollywood, thats for the addition information regarding the difference between the Jouef and Athearn system and Nigel Lawton's components.

 

Miss Prism, thats for the information. I'm hopeful that I can squeeze the reduction into the J50 body. I'll have to think about how to reduce the friction though!

[Horsetan]

I keep thinking of DAF-Variomatic whenever anyone mentions belts and pulleys.

[Horsetan]

Yes, clever design was that éh? ....

 

Certainly was - a bit of genius by Van Doorne, and race-proven. But could you make a miniature version to drive a locomotive? Would it work?

[bertiedog]

It was done on a 5 inch gauge diesel, passenger hauling, and there's really no reason it could no be scaled down, it would have to be a square section belt, not the toothed belt versions.

 

A possibility might be to do the cones with a manual lever control, adjusted by a micro servo, driven by DCC control separately to the motor speed, having both speed and gear ratio adjustable............ it might suit a big diesel in OO.

 

Stephen.

[Horsetan]

....., it would have to be a square section belt, not the toothed belt versions.....

 

Any particular reason for the change in belt?

[Pacific231G]

As promised I did ask several fellow SNCFS members about their experiences with Jouef belt drives and the general conclusion agreed with mine that they're generally quieter than the gear train but rather prone to slipping. There were also comments that using a better belt improved the slippage problem considerably. There's obviously a balance between too much belt tension adding resistance and thus poor running and too little allowing slippage and the adhesion (?) of the belt is surely a factor here. My own experience suggests but not conclusively that when they're not slipping the belt drive versions may be a bit smoother in operation.

[bertiedog]

Any particular reason for the change in belt?

 

The miniature belts do not exist in the right V sections, the 5 inch gauge one used a Gates V belt, with un-used teeth, to make a tiny DAF variomatic drive it would be forced to use round or square section belting, all that is made.

 

Variable drives exist with teeth engaged at min and max, and chain vario exist that engage at all ratios. DAF were not the only designers working on this, they were the only car maker to use the belt.

 

Several British engineering firms used the drive long before , mainly in drive machinery like lathes and specialist cloth mills.

 

As DAF were to find there are wear issues, and heating due to friction, which gears do not suffer from. Simple belt drives offer silence and durability for models as long as the right belts are used.

[hollywoodfoundry]

As promised I did ask several fellow SNCFS members about their experiences with Jouef belt drives and the general conclusion agreed with mine that they're generally quieter than the gear train but rather prone to slipping. There were also comments that using a better belt improved the slippage problem considerably. There's obviously a balance between too much belt tension adding resistance and thus poor running and too little allowing slippage and the adhesion (?) of the belt is surely a factor here. My own experience suggests but not conclusively that when they're not slipping the belt drive versions may be a bit smoother in operation.

 

One of the probable reasons for slipping is that Jouef tended to use traction tyres as well on the belt drive systems. This is a real no-no. I find that I do not get belt slippage on my mechanisms because the wheels lose traction first and spin. If this does not happen, and the belt slips, then the belt will wear, and you don't want that.

 

Wheels spinning are like a safety valve for model mechanisms. If the wheels do not spin under excessive load, then other parts of the drive system are being placed under excessive load and will wear out quickly.

 

For this reason, I do not, and will not fit traction tyres to a model. I consider them to be dangerous and damaging to model mechanisms.

[Atso]

Thanks for the comments and ideas guys.

 

Good the hear that there is some mileage in the belt and pulley system. Traction tyres are out though - lots of weight to replace I think!