Pete Harvey Posted May 5, 2010 Share Posted May 5, 2010 Can I ask why have you gone over to belt drives from Gears, other than the obvious that they are much cheaper? Pete Link to post Share on other sites More sharing options...
hollywoodfoundry Posted May 5, 2010 Share Posted May 5, 2010 Pete, Not 'much' cheaper, but certainly cheaper. I still have to have a selection of brass pulleys made and they are not cheap either. Typically a pulley is about 2/3 the cost of a gear, and in most drives there are 3 gears as against 2 pulleys. The belts are quite cheap though. The main reason is noise. My designs are modular, allowing me to produce variable wheel bases, and the basis of this is the use of worms and worm gears connected by a layshaft. This allows me to space the worms along the layshaft at any distance the customer desires. The down side is that the greatest reduction stage is at the end of the drive chain, rather than the more common position of the start of the chain. Because of this, the gears earlier on in the chain are running at higher speed, and this produces noise. Methods of reducing the noise are helical cut gears and brass/acetal/brass sandwiches, but inevitably there will be noise you cannot get rid of. If the worm was the first gear in the chain, noise would not be so much of a problem. A further problem with gears is the precision of meshing. This means the input and output shafts in a drive chain must be a precise distance apart, controlled by the size and module of the gear. Belts on the other hand are quite silent, do not have precision meshing requirements and can be spaced apart non-critically. Having a bunch of different size belts is cheap compared with the gear equivalent which not only requires a bunch of gears but a specially design etched gearbox for each design. The one disadvantage of belts is the side load it places on the motor or operating shafts. I solve that problem wherever it occurs by using tiny ball races to handle the side load. The bearings in the motors can also stand this load to quite an extent. The secret is not to place too much tension on the belt, so having the correct sized belt is important, as is the design of the pulley/belt interface. The belts by the way are not simple rubber bands, unlike rubber band drive systems used early on with some models, notably Athearn and Joueff. These are true drive belts made from a synthetic rubber, and are more akin to the belts used in your VCR or CD-ROM drive. While a normal rubber band will wear and perish with time, these drive belts are designed to last. I have always been concious of the need for quieter drive systems, so when the opportunity arose to try belt drives, I experimented with some as soon as I could. Nigel Lawton, with whom I correspond regularly, introduced me to them and the first experiments used his pulleys and belts. Now we supply each other with components from time to time. On the other hand, I have not abandoned gear drives. Many people do not trust belt drives because they cannot see past the problems that the old designs had, in particular the Athearn 'Hi-Fi' rubber belt drive. That thing was an absolute shocker in every respect. Had there been a revolution in America, the designer of that thing would have been the first one up against the wall..... (in my world anyway ) To help counter this, I always include a spare belt with every order to help allay fears, and if anyone manages to wear one out, I will supply free replacements. So far no takers. Geoff Link to post Share on other sites More sharing options...
Pete Harvey Posted May 5, 2010 Author Share Posted May 5, 2010 Geoff Thank you for that explanation I was curious why you had what seemed sudden changed from gears to belt. Pete Link to post Share on other sites More sharing options...
bertiedog Posted May 5, 2010 Share Posted May 5, 2010 Completely agree with Geoff, but if you use belts make sure that they are the right type if Geoff did not supply them....... there are nasty belts still around! Micro belts are also done by Nigel Lawton in the UK, and don't forget the Delrin roller style chain used in O gauge, it is possible to use this in bigger 00 diesel outlines....just!! The US makers Athearn, and Lionel HO, both used "O rings" as belts, not the right use at all, and Terry spring was used by Suydam and others as a coil spring "belt" drive. The ultimate answer would be toothed Gates Kevlar belts, about 1.5 mm to 2mm wide, .5mm thick, in a wide variety of lengths.....but dream on!!!! They are made for specialist uses, but no range and very costly for one off's. ( A Gates Kevlar style belt probably drives the camshaft in your car, showing how tough they are, they are used on Harley Davison as the main transmission drive, no chain.)( .....and long thin ones are used in every ink jet printer). Stephen. Link to post Share on other sites More sharing options...
hollywoodfoundry Posted May 5, 2010 Share Posted May 5, 2010 Stephen, The belts I use and the ones supplied by Nigel Lawton are from the same manufacturer. To save on costs, when I get a new size done, I send some to Nigel and vice versa. It is good to have a good stock of sizes. As you say, O rings are not good as belts. They can be used quite sucessfully as friction drives, in the manner Nigel employs them, but are not designed or made from the right material for stretch or tension applications. I recently used a set of Grandt Line chain in a drive for an O gauge mechanism for a client, it work beautifully. I used a North Yard enclosed gear box to couple an 18 series Mashima motor to one axle, then coupled the two axles together using chain. It would be a godsend if they could produce an OO or HO scale size of the same chain. The Gates Kevlar belts are extremely tempting, and some US companies produce them in quite small sizes, but again, so far nothing suitable for OO or HO. Every now and then I go searching the net to see if someone is making tiny ones. McMaster in the US even do jointing kits for theirs, but will not sell overseas any more. They claim the paperwork is too tiresome and expensive. Nevertheless, I get a friend in LA to buy belts for me and send them over. Geoff Link to post Share on other sites More sharing options...
Horsetan Posted May 6, 2010 Share Posted May 6, 2010 This is almost like stumbling upon a discussion about the DAF Variomatic transmission. Do belt drives slip in model railway use? Link to post Share on other sites More sharing options...
jwealleans Posted May 6, 2010 Share Posted May 6, 2010 I've not managed to get this to slip yet. Link to post Share on other sites More sharing options...
hollywoodfoundry Posted May 6, 2010 Share Posted May 6, 2010 Seeing that train behind the Sentinel of Jonathan's, 'I rest my case'. By the way, that is a lovely scene! Actually, depending upon the size of belt used, they can slip, which is a good thing because it protects the motor. Howver in most cases, the wheels simply spin instead. Geoff Link to post Share on other sites More sharing options...
bertiedog Posted May 7, 2010 Share Posted May 7, 2010 If the pulleys are correct in design, then slippage is highly unlikely, and with both round and square section the belt is in a V pulley, where the force causes the belt to compress into the V, and as pull increases the belt tightens further. This works with square just as well, as long as the V is adjusted to suit. Actually a lot of belt designs have them too tight adding the force of the transmission to the tension between the pulleys on each shaft. It is often said they apply more force to the bearings, but if the belt is correctly fitted it is almost slack, with very little pressure. The force applied to the bearing under load is slightly higher than gears, but they also have resultant forces as well under load, so all in all there is little extra with belts. Obviously the belt has to be tight enough to stay put, and the slack on the "un-powered" side increases under load, and the tension must be enough to stop the slack getting to a point where the belt risks riding up the V pulley and jumping off. The other answer, leaving them more slack, is to have deep sides to the V pulley to stop the belt jumping, this allows more slack and still no slip, and low pressure on the bearings. I had experience in designing miniature belt drives for some scientific instruments, and again Gates drive belts would have solved the issue, they can run slack, and do not slip if on the toothed pulleys, but can run on V sided pulleys as well, without teeth. Stephen Link to post Share on other sites More sharing options...
Ron Solly Posted May 7, 2010 Share Posted May 7, 2010 Toothed belts are used on some of Bachmann H0 locos like the Decapod & Consolidation & they run very quiet indeed. Link to post Share on other sites More sharing options...
bertiedog Posted May 7, 2010 Share Posted May 7, 2010 Toothed belts are used on some of Bachmann H0 locos like the Decapod & Consolidation & they run very quiet indeed. Yes, I saw that the other day, the UK ones don't, it seeems confined to the 0n30, and larger HO, anybody any experience of two things, a photograph and dimensions, and whether they can be bought from Bachmann or whether the Chinese makers can supply direct. Do they use them on cogs , plain pulleys in reverse, or in a V pulley? Stephen. Link to post Share on other sites More sharing options...
Horsetan Posted May 7, 2010 Share Posted May 7, 2010 ---->CLAG drive system here Link to post Share on other sites More sharing options...
bertiedog Posted May 7, 2010 Share Posted May 7, 2010 ---->CLAG drive system here This uses the Nigel Lawton/Hollywood foundry belts in smaller sizes, and works well. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted May 7, 2010 Share Posted May 7, 2010 After a crawl through several US modelling blogs and websites it seems that the belts that Bachmann use are simply not obtainable as spares, they have to return to Bachmann for replacement. It is also interesting that lots of US modellers do not know they are made in China, it comes as a surprise that Bachmann are not a US company any more, just importers. One reply states that Bachmann excuse themselves by saying export of spares is restricted by the Chinese Government.......weird excuse that one!! I wonder if they are breaking patents though? this may be the reason they are coy about selling them as separate items. It may all be different in the UK of course, spares are part and parcel of commercial sales and G/tee. The only access to these may be Hong Kong, who market anything that moves!!!!maybe a spares maker knows the suppliers of the miniature toothed belts Bachmann uses....... a thought, ...... they might even use the maker that Geoff quoted in the States, being expensive they would only buy what they need, and have no spare stock to sell, this sounds far more likely than a Government restriction. Not wanting to step on Geoff's recommendations, but some O rings can be used as belts, the narrow series above about 1 inch diameter, and Viton brand, the toughest. I have some mechanisms using these, and they have lasted, as have silicon versions in the narrow type. The key is to use them "slack", and have deep V's to get the pulley to grip. Plain rubber O rings are not any good, they stretch and can go sticky with age. All types of O rings can be used as friction drives, like Nigel Lawton uses for his miniature drives. Stephen. Link to post Share on other sites More sharing options...
Ron Solly Posted May 7, 2010 Share Posted May 7, 2010 Yes, I saw that the other day, the UK ones don't, it seeems confined to the 0n30, and larger HO, anybody any experience of two things, a photograph and dimensions, and whether they can be bought from Bachmann or whether the Chinese makers can supply direct. Do they use them on cogs , plain pulleys in reverse, or in a V pulley? Stephen. Stephen, page 3 of http://www.bachmanntrains.com/home-usa/dwg/dwgs/H817X-IS001.PDF indicates a cogged pulley & as I do not have those locos anymore ,I cannot supply photos. Motors are available as spares so presumably belts could be obtained. My friend who purchased the Decapod from me, obtained a new motor from Kernow ModelRail Centre in the UK. Link to post Share on other sites More sharing options...
hollywoodfoundry Posted May 7, 2010 Share Posted May 7, 2010 I have tried quite earnestly to find a supplier of toothed belts other than McMaster, but to no avail. Even my supplier of rubber belts does not have a clue if anyone in China is doing them. But from my point of view, obtaining them as spares would be no use to me, I need a constant, reliable supplier in large quantities if I am going to use them in drives. However, the biggest hurdle is not the belt, but the pulleys. Having them made is fiendishly expensive, as they really have to be made from an extruded section with cheeks added. The last quote I got for having that done made my eyes water. And seeing I can do almost as well with the V pulleys and square section belts, there is little reason to change. Geoff Link to post Share on other sites More sharing options...
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