lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
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Post by lesstoneuk on Nov 25, 2020 7:02:10 GMT
Thanks, greatly appreciate these links you give me. I've ordered the 150w motors, got a good deal on 3 of them. I'll see what toothed pulleys I'll need now. I was always going to fit a tensioning idler so next question is... Which side of the drive should the idler be... Drive side or trailing side in forward
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jackrae
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Post by jackrae on Nov 25, 2020 8:16:07 GMT
trailing
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
Posts: 373
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Post by lesstoneuk on Nov 25, 2020 11:38:56 GMT
Trailing will mean different idler positions on each bogie subframe. The idler on the leading subframe will have to be on top, whereas the trailing subframe will have to be on the bottom. Me thinks I'll have to work out a dual fitting so the parts I build will do both. Incidentally, had a good result on an idea I had at the weekend. The missus has an old laptop, it's got a shed load of pics on it and it's not used much. I dug out an old CAD program I used many years ago and it runs fine. Just have to relearn TOTALCAD again. Well chuffed to say the least.
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Post by ettingtonliam on Nov 25, 2020 12:29:34 GMT
Doesn't the same apply with the idler on the drive side? One on top and one underneath?
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
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Post by lesstoneuk on Nov 25, 2020 12:48:37 GMT
Doesn't the same apply with the idler on the drive side? One on top and one underneath? I'm only planning on one idler, on an adjustable swinging arm to engage more of the belt on the 16 tooth cog on the motor and keep the tension as an ideal amount. According to my calculations a 16 tooth drive cog to a 60 tooth driven cog, 112mm driving wheels and a motor rpm of 2500 will give me just under 9mph.
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stevep
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Post by stevep on Nov 25, 2020 12:51:59 GMT
9 MPH! You'll be flying. I have a speedometer on my driving trolley, and I find 5 MPH (behind my 3 1/2" Rob Roy) is quite quick enough.
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
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Post by lesstoneuk on Nov 25, 2020 13:09:52 GMT
9 MPH! You'll be flying. I have a speedometer on my driving trolley, and I find 5 MPH (behind my 3 1/2" Rob Roy) is quite quick enough. Can't be doing with high speed, too many bugs and creepy crawls in my teeth from riding a motorbike. Just done a quick recalculation using an 80 tooth driven cog and that brings top speed down to 6.58mph.
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jackrae
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Post by jackrae on Nov 25, 2020 13:10:05 GMT
But a good quality quadrature speed control means you can run at what you deem a 'sensible' speed with no loss of efficiency
I take it you appreciate the idler is a flat pulley and acts on the outside (non-toothed) side of the belt
How many teeth do you calculate to be in full contact on the drive pinion
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
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Post by lesstoneuk on Nov 25, 2020 13:21:40 GMT
But a good quality quadrature speed control means you can run at what you deem a 'sensible' speed with no loss of efficiency I take it you appreciate the idler is a flat pulley and acts on the outside (non-toothed) side of the belt How many teeth do you calculate to be in full contact on the drive pinion Yes, I know the idler runs on the rear of the belt, thinking of it I may incorporate two idlers at about 1/3 and 2/3 positions. I'd hope for 10 of the 16 cogs in the driver cog to be active.
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stevep
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Post by stevep on Nov 25, 2020 17:07:28 GMT
9 MPH! You'll be flying. I have a speedometer on my driving trolley, and I find 5 MPH (behind my 3 1/2" Rob Roy) is quite quick enough. Can't be doing with high speed, too many bugs and creepy crawls in my teeth from riding a motorbike. Just done a quick recalculation using an 80 tooth driven cog and that brings top speed down to 6.58mph. That seems better. I think that at IMLEC, they enforce a 6 MPH speed limit - but maybe that's track dependent.
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Post by delaplume on Nov 25, 2020 22:06:02 GMT
A brisk walking speed was the advice given to me when I first dabbled in "The black Art"....
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Post by steamer5 on Nov 25, 2020 23:40:35 GMT
Hi Les, A mate of mine built an electric some years ago & installed an idler / belt tensioner, after a few runs he binned it because it was using too much power..... I can’t remember his setup & can’t ask as he is no longer with us. Had another mate who was going to build his loco with 1 motor per wheel! There was just enough space between the frames for them to fit. Once again can’t ask any more question as he’s not here either. I can’t remember how he was going to control them, likely a home built controller as he was very smart at doing stuff like that
On the speed front 29 km/hr on ground level......once was more than enough!
Cheers Kerrin
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
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Post by lesstoneuk on Nov 26, 2020 0:58:54 GMT
Hi Les, A mate of mine built an electric some years ago & installed an idler / belt tensioner, after a few runs he binned it because it was using too much power..... I can’t remember his setup & can’t ask as he is no longer with us. Had another mate who was going to build his loco with 1 motor per wheel! There was just enough space between the frames for them to fit. Once again can’t ask any more question as he’s not here either. I can’t remember how he was going to control them, likely a home built controller as he was very smart at doing stuff like that On the speed front 29 km/hr on ground level......once was more than enough! Cheers Kerrin Thanks Kerrin, I'm doing one 150w brushed motor per axle mounted on a subframe. Bottom end has bearings on the axle, the top end has a slot that engages with a cross bar mounted on the bogie frame. That'll allow for up and down undulations in the track. I got the idea from an article in EIM a few years back. I'm crap at electronics, so it'll be a commercial controller... 60amp should be enough for 4 x 150w @ 24v
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Post by delaplume on Nov 26, 2020 11:24:08 GMT
Hi Leslie, Yes, that's what I'm running at the moment in my 5" Class 52...........24v feeding 4 x 150W motors in parallel via a DNO 10 controller supplied from 4QD Ltd..... Here's an early Maxitrak Class 42 showing a single, brushed motor per bogie using a toothed belt drive to one axle.....I thought this might be of some help ??
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Post by andyhigham on Nov 26, 2020 15:54:50 GMT
Rather than idlers I would make the motor mount adjustable. Idlers on the back of belts dramatically reduce their life, if you must use an idler fit it on the inside of the "slack" side
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lesstoneuk
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Retired Omnibus navigation & velocity adjustment technician
Posts: 373
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Post by lesstoneuk on Nov 26, 2020 20:00:19 GMT
Rather than idlers I would make the motor mount adjustable. Idlers on the back of belts dramatically reduce their life, if you must use an idler fit it on the inside of the "slack" side That's not really an option, the motors mount with 3 socket cap screws on the front face and there's limited room between this front face and the drive gear. Using an idler is the best way.
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jackrae
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Post by jackrae on Nov 26, 2020 22:27:55 GMT
I agree with Andy that idlers should be avoided if at all possible. However fitting them inside the belt tends to reduce one of the main purposes which (apart from setting correct tension) is to increase wrap around the drive pinion to maximise tooth contact.
As to not being able to engineer a degree of adjustment, there's always a way. If you do some work on belt design and length you really should be able to come up with a combination of belt pitch and length to suit your drive and driven sprockets such that less than say 2mm of adjustment will achieve correct belt tension. Why 2mm, well you need the belt loose to slide it onto the sprockets. Remember, tooth belts do not stretch, so once set to run with correct tension that becomes their setting for life (whatever that may mean)
Using one of the three motor mount holes as a pivot point, a slight amount of peripheral slotting on the other 2 mounting holes should give you all the adjustment you need
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Post by andyhigham on Nov 27, 2020 10:53:37 GMT
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lesstoneuk
Part of the e-furniture
Retired Omnibus navigation & velocity adjustment technician
Posts: 373
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Post by lesstoneuk on Nov 28, 2020 7:06:54 GMT
Excellent idea, I'll try that out if enough driver teeth can engage. If there's not enough then it'll have to be an idler.
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Post by coniston on Nov 29, 2020 22:35:31 GMT
I'm sure this will be a preferable solution to an idler/tensioner, even if you have to fit one or both pulleys with the belt in situ over them. It may be a bit of a fiddle but it's not as if you'll be taking them on and off regularly, if at all.
Chris D
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