Spur gears

Discuss the prototype and how to model it.
Michael Waldron
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Spur gears

Postby Michael Waldron » Wed Aug 05, 2020 3:53 pm

A7D25C49-DB71-42C4-8B2E-6DA2CF5C35EE.jpeg
Having spent around £25 per set on gears for just one loco, to furnish my tender drive reduction box and loco worm and wheel extension gearbox, I’m looking for a cheaper alternative to a Ultrascale gears.
They’re good, but I have at least another 4 locos that need a similar arrangement, and a further £200 just in gears is getting very expensive!

I designed a tender drive and flexible carriage loco gearbox to enable single drivers to be able to get traction by adding lead to the boiler and what would have been the motor and grew I area. (The worm shaft bearings fit better than appears here on the test mock up!)

Does anyone know of a supplier or maker, other than Letchworth Gear Services, who either stocks or makes gears?
Who supplies Chris Gibbons, for example?

Mike

davebradwell
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Re: Spur gears

Postby davebradwell » Wed Aug 05, 2020 4:34 pm

Chris Gibbon won't tell you where he gets his gears - he says it's his only trade secret but he'll probably sell you some, if he has the right sizes, of course.

Don't you find that putting the spur gears on the highest revving shaft increases the noise significantly? In fact it looks as if they're all metal gears at the front, too so potential for a merry racket there. By using outside brgs on the tender you could drop the motor between the wheels and possibly eliminate the spur gears completely, although these things did have big tender wheels so high axle position. They're only small locos so next size smaller motor might also be worth considering. If Cardan shaft isn't too long you can just use 0.5mm piano wire.

Can I point out that you need 2 universals and a Cardan shaft with apologies if it's just the way it's laid out that's led me to worry unduly - you do say it's a test rig. I take it you,ll fix the swinging bit, too.

DaveB

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Horsetan
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Re: Spur gears

Postby Horsetan » Wed Aug 05, 2020 10:27 pm

Branchlines may still have suitable gears in stock - they sent me their PDF price lists yesterday.

Other alternatives may be NWSL (under new ownership).
That would be an ecumenical matter.

nigelcliffe
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Re: Spur gears

Postby nigelcliffe » Thu Aug 06, 2020 8:18 am

There are outfits like KKPMO from Poland, who sell on website and Ebay as either KKPMO or Microantrieb. If there is stock, they have plastic and brass gears in a variety of sizes. (my experience of KKPMO is mixed - at their best great, but sometimes seem to disappear and not deal with significant orders )

Also, search out robotics suppliers, particularly for hobby robotics.


- Nigel

Julian Roberts
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Re: Spur gears

Postby Julian Roberts » Thu Aug 06, 2020 9:03 am

Doesn't the High Level "Tender Riser" - (or is it "Tenderiser"?) do the same job, more quietly and cheaply?

There was an article in a recent Snooze about this by Mike Ainsworth. He used a flexible tube. I recently used a Markits UJ for a remote motor within loco, which works perfectly and pretty quietly.

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Tim V
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Re: Spur gears

Postby Tim V » Thu Aug 06, 2020 2:22 pm

Look outside model railways.

Got a slot car shop near you?

I have some of the MRRC gears - I've used them on my workbench thread.
Tim V
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Michael Waldron
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Re: Spur gears

Postby Michael Waldron » Fri Aug 07, 2020 1:36 pm

Thanks for your thoughts Gents.

Yes it’s just a set up to see what it looked like a few of years ago when checking the etch was centring the gears correctly. I didn’t photograph the revised model, which sticks to the same principles but has quite a few amendments.

I asked Chris a couple of years back but also found him very reticent to discuss gear sources!

MRRC gears might well do the trick .... are they still going? I associated them with Ks motors from the 1980s! Perhaps unjustly.

Also re the Tenderiser, I wasn’t aware of its existence when I was developing my design, so went with what seemed right.
I didn’t hear about the tenderiser until I read Steve Duckworth’s excellent “Blues” article and subsequent “Trio of CR locos” in S4 News, by which time the design was complete.

Needless to say, I intended to follow suit with the ball bearing + fuel tube UV joints, though the ones in the last S4News from Eridge SR locos promotes the idea of 7mm handrail knobs as UVs....!

Not seen the Markits ones....

Mike

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grovenor-2685
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Re: Spur gears

Postby grovenor-2685 » Fri Aug 07, 2020 1:48 pm

Another option is to use gearhead motors where the reduction is built in and you just need a bevel or contrate gearset for the axle. I think Mike Edge has illustrated this in his RMweb workbench.
The drawback is that the driveshaft is in the maximum torque part of the drive so maximising the tendency to tender rock. Ideally you want the drive shaft at minimum torque/maximum speed to minimise the rocking effect and the need for a strong U?J system.
See
https://www.rmweb.co.uk/community/index.php?/topic/146364-michael-edges-workbench/&do=findComment&comment=4026473
and
https://www.rmweb.co.uk/community/index.php?/topic/146364-michael-edges-workbench/&do=findComment&comment=4014731
Regards
Keith
Grovenor Sidings

davebradwell
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Re: Spur gears

Postby davebradwell » Fri Aug 07, 2020 3:05 pm

You might be running into a conflict here. All flexible tubing is curved so has the potential, when used as a flexible joint to give an uneven drive. To minimise this effect you would choose the thinnest possible tube which might not be sympathetic to your intention to transmit a higher torque. This torque is not constant as the model negotiates rail steps, checkrails, kinks, curves, etc and a very flexible element in the later stages of the drive has the potential to cause lurching.

I don't recommend copying the single u/j design as it's only by a miracle of careful alignment that it works at all and does not permit the tender to twist with respect to the loco. It can only be used with compensation so you're lumbered with the extra noise and bumpy ride from a rigid axle. Yes, other folk claim it works, too but it's much easier to do the job properly with 2 joints and a single universal coupling is a very poor way of taking a drive round a corner especially as singly, they don't give a constant velocity drive but 2 lurches per revolution. Even with the correct 2 couplings they should, with our type, be arranged close to a straight line.

For years I've used a stock of the NWSL couplings bought from Dynadrive. I see they are available again but I have to find a UK stockist to avoid ordering from US - it's not the duty but the surprise Royal Mail "handling charge" that cost me on my last attempt.

DaveB

Michael Waldron
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Re: Spur gears

Postby Michael Waldron » Sat Aug 08, 2020 6:52 am

Thanks Keith and Dave for those observations.

I can’t quite locate the model of n20 motor and gearbox - presumably it’s an eBay Chinese one?
I have a small drum motor with enclosed gearbox driving my turntable very effectively.

Dave, I agree regarding the need for two uv joints, having had an Isetta in my youth (60s) and had to replace the two rubber doughnuts that fitted the spiders on the main engine to gearbox driveshaft... not unlike ones I believe were fitted to Hillman Imps and Singer Vogues in the 70s!

Not wishing to cast any aspersions on the now departed guru Sharman, did he always propound the need for two uvs?
My copy of his little blue Flexichas book is buried somewhere in the railway cabin!

Mike

davebradwell
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Re: Spur gears

Postby davebradwell » Sat Aug 08, 2020 9:34 am

Mike, I would hope Mike Sharman always proposed 2 universals, being a proper engineer and all that but with the appropriate compensation scheme it's possible to make one joint work but with great care and understanding and not going round a corner. I'm sorry to go on about it on your thread but it's one of the practices on my target list that is in danger of being encouraged by forums whereas it's better and far easier to use 2 joints as there's no need for any accurate alignment. It's only about hiding the driveshaft is it not? You may have noticed that swinging arms on gearboxes are another sensitive area.

It always amazes me that suggestions aimed at reducing the noise of the electric drive are met with little general enthusiasm. I can only hope that the silent majority are more impressionable. Anyway, you now have a source of plastic gears so with a sensible ratio all will be fine.

.....and you haven't even mentioned the bogie arrangement yet!

DaveB

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grovenor-2685
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Re: Spur gears

Postby grovenor-2685 » Sat Aug 08, 2020 9:52 am

I can’t quite locate the model of n20 motor and gearbox - presumably it’s an eBay Chinese one?
I have a small drum motor with enclosed gearbox driving my turntable very effectively.

I gave a link a few posts back, most of the gearboxes seem to be designed for a 100 rpm output, but there are plenty of gears in them at under £2 for the whole gearbox compared to your £25.
Oops sorry, my post with Ebay link seems to have got lost, I'll have to look it up again and add it here. Scrolling someway down found the gearboxes on sale without the motors.
https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=N20+motors&_sacat=0
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Keith
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Julian Roberts
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Re: Spur gears

Postby Julian Roberts » Sat Aug 08, 2020 9:55 am

Just writing to concur that double UJ is far better than single, even in my 0-4-4T loco where the motor is almost but not absolutely in line with the gearbox. Previously I had a Branchlines single UJ as there wasn't room for a double, the Markits double UJ makes the loco able to run considerably better. Sorry don't know if Markits still sell them.

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ianlbsc
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Re: Spur gears

Postby ianlbsc » Sat Aug 08, 2020 11:10 am

https://www.rmweb.co.uk/community/index ... s/page/37/

is the start of the bevel gear drive from Mike Edge.
Cheers Ian

Michael Waldron
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Re: Spur gears

Postby Michael Waldron » Tue Aug 11, 2020 6:27 am

ianlbsc wrote:https://www.rmweb.co.uk/community/index.php?/topic/45248-judith-edge-kits/page/37/

is the start of the bevel gear drive from Mike Edge.
Cheers Ian


Thanks Ian

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CDGFife
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Re: Spur gears

Postby CDGFife » Tue Aug 11, 2020 4:07 pm

If you don't want to wait for the really cheap ones from china I got my 0.5MOD 20T mitre gears next day from here:
https://www.beltingonline.com/dbm05-20- ... rqfcdd7a07

To go in here with a 300 rpm N20 motor:
Kelly Chassis.jpg
Kelly Chassis.jpg (288.07 KiB) Viewed 2358 times


I needed to cut off the boss on the axle mounted one and widen the bore slightly but I've found the Delrin seems to sweat onto the axle and they seem to stay put and drive well without any fixing. Admittedly this little chassis dos not pull too much but I've not managed to spin them yet, which was a real surprise!!

I also have some 16T smaller mitres from here:
https://www.gearsandsprockets.co.uk/met ... tre-gears/
to try as a further space saver.

Cheers

CDG

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Horsetan
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Re: Spur gears

Postby Horsetan » Tue Aug 11, 2020 4:37 pm

CDGFife wrote:....I also have some 16T smaller mitres from here:
https://www.gearsandsprockets.co.uk/met ... tre-gears/
to try as a further space saver....


Interesting :thumb
That would be an ecumenical matter.

DougN
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Re: Spur gears

Postby DougN » Wed Aug 12, 2020 6:31 am

I think this option really has merit. thanks for putting this up. I have more than enough to do but the mind does race a little when I am away from modelling, You know at work when procrastinating... :twisted:

I have been looking on line and there appears to be a lot of N20 motor gearbox combinations available. (ie the RPM and voltages) they also seem very small but quite powerful (thats with out having one to play with)
Doug
Still not doing enough modelling

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CDGFife
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Re: Spur gears

Postby CDGFife » Wed Aug 12, 2020 8:01 am

I've certainly found this one to be powerful and damn near impossible to stall. It consistently turns the wheels at around 1v on my DC rolling road!

If there is a drawback it is noise. This combination is nowhere near as quite as the Highlevel gearbox and motor combo I use normally on Cadhay's locos. Whilst that does not bother me too much it will for some.

Chris

Michael Waldron
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Re: Spur gears

Postby Michael Waldron » Thu Aug 13, 2020 6:18 pm

CDGFife wrote:If you don't want to wait for the really cheap ones from china I got my 0.5MOD 20T mitre gears next day from here:
https://www.beltingonline.com/dbm05-20- ... rqfcdd7a07

To go in here with a 300 rpm N20 motor:
Kelly Chassis.jpg

I needed to cut off the boss on the axle mounted one and widen the bore slightly but I've found the Delrin seems to sweat onto the axle and they seem to stay put and drive well without any fixing. Admittedly this little chassis dos not pull too much but I've not managed to spin them yet, which was a real surprise!!

I also have some 16T smaller mitres from here:
https://www.gearsandsprockets.co.uk/met ... tre-gears/
to try as a further space saver.

Cheers

CDG

Many thanks for that.
Mike

Michael Waldron
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Re: Spur gears

Postby Michael Waldron » Thu Aug 13, 2020 6:19 pm

Incidentally, which motor rpm is recommended as a general rule, bearing in mind all the mitre gears are 1:1?
Mike

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CDGFife
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Re: Spur gears

Postby CDGFife » Fri Aug 14, 2020 8:08 am

I've found the 300 rpm motor with 1:1 mitre works well on my 0-4-0 shunter. I was a bit worried about low speed running but that seems to be fine with the 300 rpm too. I've got 100 and 60 rpm motors to try also and I've also got the 0.5 MOD 16T mitre to try which in theory should work with the 20T to either reduce or increase the ratio slightly, but the straight 300rpm and 1:1 mitre worked so well I haven't got round to it yet.

Cheers

Chris

davebradwell
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Re: Spur gears

Postby davebradwell » Fri Aug 14, 2020 10:50 am

Bevel gears. Just to point out that your 16 and 25t gears will not mesh together properly - the teeth on the 16 taper more sharply than those on the 25. Bevel gears come as pairs with the inclination of the teeth pointing at the shaft intersection so if ratio is other than 1:1 then angle is not 45 deg. This doesn't mean they won't drive, of course but you'll only get point contact on the teeth.

I'll also add that stepping up ratios are always avoided unless you're desperate and the overhang of the bevel from the gearbox bearing should be minimised.

DaveB

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CDGFife
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Re: Spur gears

Postby CDGFife » Sat Aug 15, 2020 8:13 am

Thanks Dave.
That also explains why the mitre gears are sold in pairs.

Fortunately I've found the 20T mitre pair worked fine with the 300 rpm N20 but I might try the 16T just to see how bad (or not) the meshing is with a 20T. Looking at them, they both state they have a 45 degree angle and certainly when held together in mesh they seem to settle on around a 90 degree intersection angle. Could this be because they are true mitre gears rather than just bevels? The website I had them from also sells bevels (again in pairs) and some of them appear not to have a 45degree angle. (Showing my lack of gear-related knowledge I know!!! ;) )

Cheers

Chris

davebradwell
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Re: Spur gears

Postby davebradwell » Sat Aug 15, 2020 11:05 am

Mitre gears are just the special case of bevel gears that give 1:1 ratio and the teeth form a 45 deg cone. The cone is drawn to the intersection point of the shafts so when any other ratio is required then the angle to give a proper mesh will not be 45 - this keeps the taper of the teeth on each gear the same. You'll see that your 25t bevel has a bigger cone than the 16t so each tooth (which starts at the same width) tapers to 0 at a smaller angle and they get closer together at different rates. Judge for yourself whether the mesh of your imperfect pair is good enough; I think greater engineering sins have been committed by modellers but hopefully it will now be an informed judgement. Ensure your gearbox shaft points at centre of axle, although I suspect your mis-mesh might have increased tolerance to error here.

Gear design is an interesting subject and there's plenty on-line - looking at a few photos of bevels will clarify this stuff on cone angles. You'll also find spiral bevels, which are fascinating. Never designed bevels myself, just came in on the end of a job once - more a worm man. Look up skew gears, too as another way of doing the same thing. A useful observation from an eminent modeller in the past is that course gears give a less intrusive noise than fine as the frequency is lower - more a rumble than a whine.

We're a long way from where this started and back to the danger of being dominated by the row from metal gears. Perhaps this matters more in a steam outline model than a small diesel - the Ruston88 in Low Fell Engineers' Storeyard gave out terrible whining and grinding noises. I usually combine a low gear ratio with decent electronic motor drive to reduce noise but feel unsure how this will work out with what is probably a cheap 3 pole motor. The bevels give a more efficient drive than a worm so this is in your favour.

DaveB


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