Debs. Posted September 8, 2013 Share Posted September 8, 2013 I`m not a big fan of (traditional) 'worm and wheel' drivelines for models and have been considering a simple and quiet alternative...... Perhaps other older forum members might remember the Hoover Junior vacuum cleaner of the 1960`s era.....it used a round cross-section rubber belt to transfer drive directy from the motor`s metal spindle to the beater-bar (situated in front and below the motor axis); the drive also turning 90 degrees in the process. The motor spindle had been machined into a shallow 'Vee' (to keep the belt centred) and the beater bar having a half-round shaped groove to accept the round form of the belt. The drive worked well and belt life was good; with little or no slippage. I`ve located an affordable 12v. motor/precision planetary gearbox combo. of suitable physical size and reduction-ratio and wonder if this simple right-angle (twisted) belt-drive concept might work in my present project: a 7mm. scale, 0-6-0 industrial diesel loco. There are good quality 'O rings' in a variety of synthetic polymer compounds available and in all possible cross-sectional sizes and diameters from which to select a drive-belt to connect a couple of simply machined small diameter brass pulleys: one for the 135-1 gearbox output shaft and one for the driven axle.......because the motor/gearbox unit already provides the reduction, the pulleys could simply be of equal (small) diameter and in suitable proximity to permit the 90 degree change of direction. I hope I`ve explained the concept coherently......comments and suggestions would be welcomed. Does anyone know of this right-angle belt drive idea has been tried/used previously? Link to post Share on other sites More sharing options...
raymw Posted September 8, 2013 Share Posted September 8, 2013 Hi Debs, iirc, lone star, about 60 years ago, early n gauge (well it would happily? run on half the width of Hornby dublo), used a small rubber band, straight from in-line motor shaft to transverse axle. You will be stuck to get enough grip - keep the band tight - strain on bearings, overheating due to slipping, flexing and many other techy probs. But try it, it may well work. There are different qualities of 'rubber' in O rings, too. Best wishes, Ray Link to post Share on other sites More sharing options...
Grovenor Posted September 8, 2013 Share Posted September 8, 2013 I used to have one of those Trebl0lectrics, a class 24 Bo Bo it used 4 rubber bands, one per axle, worked fine except the gear ratio not really enough so a bit too fast. The axle was essentially a drum almost of the wheel diameter so the rubber bands only just cleared the rail head over points. I believe Athearn used to do something similar in H0 but I never saw one of those. Keith Link to post Share on other sites More sharing options...
Gordon A Posted September 8, 2013 Share Posted September 8, 2013 Debs, Have you had a look at Nigel lawton's web site? http://www.nigellawton009.com/DriveComponents.html Gordon A Bristol Link to post Share on other sites More sharing options...
billbedford Posted September 8, 2013 Share Posted September 8, 2013 You maybe have difficulties if you have the belt driving the axle. This is because the torque needed to drive your loco may overcome the friction provided by the belt. It is generally better to have a belt earlier in the drive chain where the torque between stages is less. When Ted Scannell was developing some of these gearboxes he found that a belt on the final part of the drive would slip. Link to post Share on other sites More sharing options...
Horsetan Posted September 9, 2013 Share Posted September 9, 2013 This sort of reminds me of the days of the Daf Variomatic system. Link to post Share on other sites More sharing options...
RMweb Gold Oldddudders Posted September 9, 2013 RMweb Gold Share Posted September 9, 2013 This sort of reminds me of the days of the Daf Variomatic system. Which I think spawned the CVTs that are a viable option on many cars these days. Link to post Share on other sites More sharing options...
Horsetan Posted September 9, 2013 Share Posted September 9, 2013 Which I think spawned the CVTs that are a viable option on many cars these days. Yes but I think they rely on steel rather than rubber belts nowadays. I don't think you could miniaturise it (not yet, anyway) for use in 3.5/4mm scale. Wasn't the DAF the car that you could drive equally fast in reverse as forwards? Link to post Share on other sites More sharing options...
burgundy Posted September 9, 2013 Share Posted September 9, 2013 Debs An example of rubber band drive below, taken from http://www.rmweb.co.uk/community/index.php?/topic/63652-a-small-problem……/page-2 This uses a Nigel Lawton motor and a gearbox from Mousa Models. Hope this helps Best wishes Eric Link to post Share on other sites More sharing options...
Horsetan Posted September 9, 2013 Share Posted September 9, 2013 ^ Yes, but that one still involves a worm-and-wheel in the equation, which is what Debs is trying to eliminate. Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted September 9, 2013 RMweb Gold Share Posted September 9, 2013 I'm not sure about the tensioning required to transmit the drive, but if it were too much I'd be concerned about the side loading on the motor shaft. However, if one used an idler shaft and fairly large pulley wheels, slippage and side loading would be avoided. (See belt driven machinery in old factories for example) But if the belt snaps, you will have to dismantle the wheelset in order to fit a new one! Regards Richard Link to post Share on other sites More sharing options...
trisonic Posted September 9, 2013 Share Posted September 9, 2013 I've seen a custom chopper motorbike with friction final drive. how effective it was over the long term I cannot say. About 100bhp at the friction wheel which bore directly onto the tire. Best, Pete. Link to post Share on other sites More sharing options...
PatB Posted September 9, 2013 Share Posted September 9, 2013 Yes but I think they rely on steel rather than rubber belts nowadays. I don't think you could miniaturise it (not yet, anyway) for use in 3.5/4mm scale. Wasn't the DAF the car that you could drive equally fast in reverse as forwards? Certainly was. The first car I drove regularly after passing my test was a 1967 Daf Daffodil. Being 18 and stupid you can be sure I tried the very-fast-in-reverse thing. Fortunately I twigged that steering self centring doesn't work in reverse before anything too horrendous happened. The belt CVT was an excellent system. As for belt drive on models, a belt that is too long will cause problems with "springiness" on starting and stopping. One that is too short may be overly sensitive to tension adjustment, being difficult to keep tight enough to work whilst not being so tight as to cause excessive friction or bearing wear. Using the biggest pulleys possible will help with avoiding belt slip. Keeping the pulleys close to equal size will keep as much of the belt in contact with both pulleys as possible. Link to post Share on other sites More sharing options...
HAB Posted September 9, 2013 Share Posted September 9, 2013 Just comment about a "right angle drive" - which was the OP's question. You CAN have a belt driving through a right angle (as per the Hoover example) but NOT if it has to go in both directions. (there is an exception to that if idler pulleys are used which would be a bit complex!) What you will find if you do try it, is that you can set it up to run in one direction but that the belt will always try to come off in the other. Although you might lessen the effect by having deep grooves, this means that the drive becomes hopelessly inefficient and all the motor effort goes into warming up the belt. I also agree with comments above that the belt should be the first stage, not the last for all the reasons given. Sorry to rain on the party! Cheers, Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted September 9, 2013 Share Posted September 9, 2013 Alternative protection for motor shaft, two belts, horizontally opposed, One lay shaft can be left idle, or run the chuff creator of a smoke mechanism or WHY. I'd like an excuse to use a belt to turn a driveline with a smal reduction, then a spur gear stage for the final reduction to the drive axle. I've seen a custom chopper motorbike with friction final drive. how effective it was over the long term I cannot say. About 100bhp at the friction wheel which bore directly onto the tire.. Should be made compulsory if my preferred solution of removing the engine from motorbikes not be adopted. Will last less than minute if the red mist comes down, very ineffective power transfer in the wet. Major motorcycle safety advance. Link to post Share on other sites More sharing options...
Debs. Posted September 9, 2013 Author Share Posted September 9, 2013 .......But if the belt snaps, you will have to dismantle the wheelset in order to fit a new one! Which I have had to do several times over the years when using hollow-ground (brass) worm & wheel drives....... The 12 v. axial-motor and oil-filled planetary gearbox (135-1 ratio) unit has roller bearings on its 3/16" dia. output shaft, so I doubt that lateral forces from the belt will be too much of an issue. I particularly wanted to have a driveline that would freewheel/coast (if only a litle) without applied power and be quieter than right-angle gearsets (bevel or worm varieties). Link to post Share on other sites More sharing options...
edcayton Posted September 9, 2013 Share Posted September 9, 2013 An old Peugeot model (204?) had a fan belt that drove through 90 degrees. I remember seeing one and being amazed. Unfortunately I can't find a picture. Ed Link to post Share on other sites More sharing options...
shortliner Posted September 9, 2013 Share Posted September 9, 2013 The Athearn RDC and several of their early models like the Hustler switching loco, used that system - although they were a bit prone to Jack-rabbit starts, and drag-race motoring - I see no reason why a planetary gearbox with a low-speed output, final drive, shouldnt work - although the friction of the lazzy-band may well prevent coasting, even if you add a flywheel - you might really need some form of centrifugal clutch Link to post Share on other sites More sharing options...
Arthur Posted September 9, 2013 Share Posted September 9, 2013 Howard, I'm unclear on the inability for such a drive system to work in forward and reverse? I too had a Trebl0lectric set, Baby Deltic, back in the 60's. A crude set up admittedly, but it worked both ways without problem. I'm trying to visualise, without success, how the forces differed in forward and reverse, isn't it 'symmetrical' so to speak. Not saying you're wrong, just curious. Link to post Share on other sites More sharing options...
Horsetan Posted September 9, 2013 Share Posted September 9, 2013 ....you might really need some form of centrifugal clutch Only one choice here: Brimalm (Sweden). Link to post Share on other sites More sharing options...
raymw Posted September 9, 2013 Share Posted September 9, 2013 Hi Debs, Is there room to get in a bevel gear set? Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted September 9, 2013 Share Posted September 9, 2013 Howard, I'm unclear on the inability for such a drive system to work in forward and reverse? I too had a Trebl0lectric set, Baby Deltic, back in the 60's. A crude set up admittedly, but it worked both ways without problem. I'm trying to visualise, without success, how the forces differed in forward and reverse, isn't it 'symmetrical' so to speak... It is symmetrical. If you watch such an elastic friction band over two shafts arrangement as in the old TrebleOlectric chassis in operation you will see the band position shift slightly with reversals. Should be no more likely to run off the pulley in one direction than the other if the set up is genuinely symmetric. But symmetry is fine in theory, may not be achieveable in practise. Even if the mechanical set up of the two shafts is perfect, should the band develop any sort of set from being operated more in one direction, there's an assymetry just waiting to cause trouble. All that said, if my childhood play with Meccano's spring steel driving bands over pulleys operated successfully forward and reverse with a 'by eye' assembly of those puleys in a right angle power transfer between motor and the winding drum gearbox, I really don't see such problems as insoluble. (Of the lack of a sufficiently strong cord to support the funicular car this set up was powering, and the inevitable pendulum drop when the cord broke, directing the car straight through a bay window pane, the less said the better.) Link to post Share on other sites More sharing options...
Arthur Posted September 9, 2013 Share Posted September 9, 2013 Sounds reasonable 34C, I can certainly see how any asymmetry could throw it out. Link to post Share on other sites More sharing options...
HAB Posted September 9, 2013 Share Posted September 9, 2013 Sounds reasonable 34C, I can certainly see how any asymmetry could throw it out. Hello Arthur, Let me try to explain why a right angle drive SHOULD be asymmetrical. The diagram shows the view from above. You can see that the part of the belt which runs in tension is running directly in line with both pulleys. In this way, the load of the drive cannot act to pull the belt off either pulley. Meanwhile the part of the belt which is not under tension, runs at the necessary angle to the pulleys but, because it is not under tension, can be easily guided by the pulley flanges (in fact, the flanges are not doing much - for a flat belt, just a small crown is necessary - the belt will not come off even without flanges). You can easily see that if this were run barse ackards, then the belt would simply pull over the drive pulley flange. 34C has already mentioned observing the belt moving when reversed - this is because the drive will always seek out the configuration shown - even when the pulleys are not laid out for it.. Just to emphasise the last bit of my first post:- of course you CAN make a symmetrical version of this by positioning one pulley centrally over the other but now you are reliant on the flanges to keep the belt in place and that causes a huge loss of efficiency (in other words, it is equally "bad" in both directions!) My question is this :- why on earth would any one want to put a hugely inefficient drive in their locos? It would cause unreliable slow starts, loss of haulage power and the belt would wear in no time. There are some very efficeint gear drive set-ups available - here is one in 4mm http://www.cometmodels.co.uk/ This really is excellently engineered and the crossed helical first stage is miles better than anything else previously available. I also understand that Slaters do something similar but I have not actually played with one of their. I note what other posters have said and I don't want to sound disrespectful, but I hardly think Treblo or Meccano could be described as examples of 21st Century cutting edge engineering solutions and the DAF PIV was brilliant (but quite inefficient - hence no imitators) but NOT scalable to our sizes! Hope that helps! Link to post Share on other sites More sharing options...
HAB Posted September 9, 2013 Share Posted September 9, 2013 I`m not a big fan of (traditional) 'worm and wheel' drivelines for models and have been considering a simple and quiet alternative...... Hello Debs, You are not alone, but for all the reasons above, I am not convinced that belts are the way forward. I mentioned the Comet gearbox above - would this (with a 1/8") axle diameter "do" for your project? If not, I am sure that, if you speak with Mr Comet, I and sure that a solution using a 3/16" bore final drive could be concocted - after all, these are "off the shelf" industrial gears. Otherwise, look at Slater's site - they have something similar. From a good engineering point of view, crossed helical gears are the most efficient solution. Best wishes, Link to post Share on other sites More sharing options...
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