Wright writes.....

[Tony Wright]

For the last picture I showed of the Heljan O2s, I did a tight crop. 

 

It gave a 'letterbox' image, which wasn't very satisfactory.

 

So.................

 

 

Here's the full frame. Much better I think in context, because these latest Heljan O2s are superb 'layout locos'. 

 

 

[1471SirFrederickBanbury]

7 minutes ago, thegreenhowards said:

I know very little about the engineering involved in gearboxes. But when I started dabbling in a O gauge, I quickly discovered helical gears and now use nothing else. They are so smooth, quiet and powerful while drawing lower amps - important in O gauge, especially with DCC decoders.

 

I can’t understand why helical gears don’t feature in 00 gearboxes.

 

Andy

helical gears have been around for a long while, but they're generally more expensive to produce.  I think you may be referring to gearboxes with crossed helical gears though.  can you back-drive said gearboxes?  the smoothness and quietness may just be that they were finished with a gear shaver, which corrects the slight defects found in plain hobbed, cast, and milled gears.

[Tony Wright]

15 minutes ago, thegreenhowards said:

I know very little about the engineering involved in gearboxes. But when I started dabbling in a O gauge, I quickly discovered helical gears and now use nothing else. They are so smooth, quiet and powerful while drawing lower amps - important in O gauge, especially with DCC decoders.

 

I can’t understand why helical gears don’t feature in 00 gearboxes.

 

Andy

Good evening Andy,

 

Are these helical gears in these 4mm Markits and Comet gearboxes?

 

 

 

Helical or not, they work superbly.

 

Regards,

 

Tony. 

 

 

[t-b-g]

5 hours ago, 1471SirFrederickBanbury said:

Even better would be a double enveloping/globoid worm gear.  This is the most efficient form of worm gear set, but bevels are still better due to the ability to back-drive. https://www.youtube.com/watch?v=4yibOUMWYNg&pp=ygUbZG91YmxlIGVudmVsb3Bpbmcgd29ybSBnZWFy 

 

 

Having seen the Sid Stubbs gearboxes at first hand, it would absolutely impossible to improve on them in terms of the quality of construction and the smoothness of the drive. They have no detectable backlash and they run absolutely smoothly in either direction. Running them backwards, by turning the wheels, requires a small amount of pressure to turn the worm wheel but running them the correct way there is no resistance that can be felt by hand. There will obviously be some but it so small as to be of no consequence.

 

I can understand why the gears illustrated would be more efficient but trying to make them would be beyond most people. The ones illustrated look like 3D printed examples. If anybody can make ones that work as smoothly as the Sid Stubbs gears without using CAD/CNC techniques, I would be hugely impressed.

 

You clearly have some in depth knowledge of engineering matters, far more than I do. I would recommend the article by Sid in MRJ if you haven't seen it. It would need some engineering background to fully appreciate it.

[thegreenhowards]

3 hours ago, 1471SirFrederickBanbury said:

helical gears have been around for a long while, but they're generally more expensive to produce.  I think you may be referring to gearboxes with crossed helical gears though.  can you back-drive said gearboxes?  the smoothness and quietness may just be that they were finished with a gear shaver, which corrects the slight defects found in plain hobbed, cast, and milled gears.

I am no expert - I just know what I like! It’s the gearboxes listed here as the ex Ron Chaplin MT Helical Range. They are back driven if, by that, you mean that the locos wheels can turn the motor like a Portescap. 

 

https://www.mscmodels.co.uk/motor-gearboxes

Andy

[thegreenhowards]

3 hours ago, Tony Wright said:

Good evening Andy,

 

Are these helical gears in these 4mm Markits and Comet gearboxes?

 

 

 

Helical or not, they work superbly.

 

Regards,

 

Tony. 

 

 

Good evening Tony,

 

I don’t think they’re helical. Can the wheels turn the motor on those gearboxes?

 

regards

 

Andy

[Izzy]

The helix is the angle that the gear teeth sit relative to the shaft. Nearly all worm gears have helical cut worm wheels, cut to match the angle of the worm they run with. The helix angle depends on the worm diameter. The smaller the worm diameter the more efficient the gears will be for the same tooth size as the surface area of the worm is less per revolution, (just basic engineering). 

 

Crossed helicals are where the teeth sit at 45degrees. Slaters used to produce a 3-1 crossed helical box to be used in conjunction with their coreless motors with spur gear reduction. I think what needs to be taken into consideration is that with such gears as these the forces involved mean that there is as much side force produced as there is forward movement. So, bespoke gearboxes are required that have thrust washers etc. to contain such forces to allow the full benefit of the forward movement. That the benefit of the higher efficiency isn’t lost in side thrust friction.
 

Given such gears also require generally a lot of space to achieve the level of gear reductions normally used in small scale model locos, the High Level range of gearboxes are a really good compromise between high efficiency and practical application, and benefit from having the worm reduction first and the spurs thus running at slower rates, as do many of those boxes illustrated in previous posts. This is  helpful as spur gears running at high rpm always generate noise, normally in the case of small tooth form sizes, a ‘whine’. Helical cut spurs gears do offset this to a certain degree, but again it all comes at a cost in terms of manufacturing costs. 
 

Bob

[Tony Wright]

7 hours ago, thegreenhowards said:

Good evening Tony,

 

I don’t think they’re helical. Can the wheels turn the motor on those gearboxes?

 

regards

 

Andy

Good morning Andy,

 

No, they can't.

 

The gears are certainly cut at an angle and they're quiet when running, even under heavy load.

 

One of the Markits gearboxes I showed was used in an ACE P2 I made...........

 

 

 

 

Which Ian Rathbone painted to perfection.

 

There's an amusing story behind this (I found it amusing, anyway). I had some splendid chaps visit one day. They model in P4/S4 (yes, I even have modellers who build things 'accurately'!). In typical Wright 'showing off mode', I put this loco on 14 kit-built bogies on Bytham and wound it up to over 90. Round and round it went, again and again. Graciously, I was complimented on the loco's performance, but the group stated to a man that 'we couldn't live with the narrow gauge and coarse wheels'. Fair enough, but a couple of months later I watched one of the group's P4 layouts at a show. A 2-6-2T and two carriages couldn't make it from one end of the (straight) run without falling off every few inches! 

 

Have others built Markits gearboxes?

 

 

I have this one to install in a 9F (it appears to have an extra worm!). 

 

It's designed (though not exclusively) to fit into a 9F, the idea being that the drive is on the fourth axle, with the motor/gearbox forming a horizontal 'U'-shape; meaning it's completely invisible with the body on.

 

 

As here, on this Hornby/Comet conversion.

 

One last question, to all. Has anyone else built an ACE 4mm kit?

 

Regards,

 

Tony. 

 

 

 

 

[Barclay]

6 minutes ago, Tony Wright said:

Good morning Andy,

 

No, they can't.

 

The gears are certainly cut at an angle and they're quiet when running, even under heavy load.

 

One of the Markits gearboxes I showed was used in an ACE P2 I made...........

 

 

 

 

Which Ian Rathbone painted to perfection.

 

There's an amusing story behind this (I found it amusing, anyway). I had some splendid chaps visit one day. They model in P4/S4 (yes, I even have modellers who build things 'accurately'!). In typical Wright 'showing off mode', I put this loco on 14 kit-built bogies on Bytham and wound it up to over 90. Round and round it went, again and again. Graciously, I was complimented on the loco's performance, but the group stated to a man that 'we couldn't live with the narrow gauge and coarse wheels'. Fair enough, but a couple of months later I watched one of the group's P4 layouts at a show. A 2-6-2T and two carriages couldn't make it from one end of the (straight) run without falling off every few inches! 

 

Have others built Markits gearboxes?

 

 

I have this one to install in a 9F (it appears to have an extra worm!). 

 

It's designed (though not exclusively) to fit into a 9F, the idea being that the drive is on the fourth axle, with the motor/gearbox forming a horizontal 'U'-shape; meaning it's completely invisible with the body on.

 

 

As here, on this Hornby/Comet conversion.

 

One last question, to all. Has anyone else built an ACE 4mm kit?

 

Regards,

 

Tony. 

 

 

 

 

Looking at the label it is perhaps supplied with worms for both 1.5mm and 2mm to save them having to make 2 different products?

Not built one of these though - Branchlines and High Level for me.

[Bucoops]

7 minutes ago, Tony Wright said:

Good morning Andy,

 

No, they can't.

 

The gears are certainly cut at an angle and they're quiet when running, even under heavy load.

 

One of the Markits gearboxes I showed was used in an ACE P2 I made...........

 

 

 

 

Which Ian Rathbone painted to perfection.

 

There's an amusing story behind this (I found it amusing, anyway). I had some splendid chaps visit one day. They model in P4/S4 (yes, I even have modellers who build things 'accurately'!). In typical Wright 'showing off mode', I put this loco on 14 kit-built bogies on Bytham and wound it up to over 90. Round and round it went, again and again. Graciously, I was complimented on the loco's performance, but the group stated to a man that 'we couldn't live with the narrow gauge and coarse wheels'. Fair enough, but a couple of months later I watched one of the group's P4 layouts at a show. A 2-6-2T and two carriages couldn't make it from one end of the (straight) run without falling off every few inches! 

 

Have others built Markits gearboxes?

 

 

I have this one to install in a 9F (it appears to have an extra worm!). 

 

It's designed (though not exclusively) to fit into a 9F, the idea being that the drive is on the fourth axle, with the motor/gearbox forming a horizontal 'U'-shape; meaning it's completely invisible with the body on.

 

 

As here, on this Hornby/Comet conversion.

 

One last question, to all. Has anyone else built an ACE 4mm kit?

 

Regards,

 

Tony. 

 

 

 

 

 

I have built a couple of 7mm ones, they work very nicely. I've only built High Level for 4mm - which as we know also work very nicely as well.

[Captain Kernow]

16 minutes ago, Tony Wright said:

Have others built Markits gearboxes?

No, I haven't and I didn't realise that they produced them. I would certainly be interested in putting one in a future loco build, but is anyone aware of whether they are currently available, given the fact that Mark Arscott is sadly unwell?

 

[Bucoops]

40 minutes ago, Captain Kernow said:

No, I haven't and I didn't realise that they produced them. I would certainly be interested in putting one in a future loco build, but is anyone aware of whether they are currently available, given the fact that Mark Arscott is sadly unwell?

 

 

The ones I have seen have always been on ebay etc.

 

Although Roxey show one type in stock - https://www.roxeymouldings.co.uk/product/616/r38-1-381-gearbox/

Edited yesterday at 08:48 by Bucoops
add Roxey

[Pebbles]

13 hours ago, Michael Edge said:

I used to do that with Triang gears, worked OK at the time.

I believe that the thread is 1/4" Whitworth. However, the triang TT3 worm was single start and could be used.

[Tony Wright]

2 hours ago, Captain Kernow said:

No, I haven't and I didn't realise that they produced them. I would certainly be interested in putting one in a future loco build, but is anyone aware of whether they are currently available, given the fact that Mark Arscott is sadly unwell?

 

Good morning Captain,

 

I've spoken to Mark a month ago and he's under treatment. He's remarkably stoic, and fulfilled an order for me. 

 

It's probably not universally known, but he makes the gears for several other gearbox manufacturers. 

 

Like all gearboxes, the Markits examples have to be assembled with care, but they run superbly if this is observed. One huge advantage they have over other designs (in my experience) is that the motors can be fixed in place/removed without the necessity of removing the worm or even taking a 'box out of a chassis. The screw fixings are outside the gearbox. 

 

Regards,

 

Tony. 

Edited yesterday at 10:55 by Tony Wright
clumsy grammar

[Tony Wright]

2 hours ago, Barclay said:

Looking at the label it is perhaps supplied with worms for both 1.5mm and 2mm to save them having to make 2 different products?

Not built one of these though - Branchlines and High Level for me.

Thanks,

 

Of course - I should have read the label!

 

Regards,

 

Tony. 

 

[Tony Wright]

Three gearboxes I've had entire satisfaction with are these..............

 

 

Comet, Markits and Branchlines.

 

All of these are two-stage, which has the advantage (if necessary) of being able to rig a 'tubby' motor above the frames - important if one models in OO using 'narrow' frames. 

 

All are designed to take a Mashima motor (I bought a stash of all sizes once the news got out about the motors no longer being available). 

 

 

Or, in the case of this Little Engines J11, to be able as well to completely hide the motor in the firebox.

 

This is a Comet box, modified (by Comet) to accept a Canon motor after Mashima's demise. 

 

 

[Tony Wright]

A bit more done on the DJH A1s..............

 

As mentioned, I was able to use one set of OO tender frames I already had.

 

But, needed to make a second set............

 

 

I wonder how others get on in making DJH A1 (and A2) tender chassis. I'm lucky, in having grown a 'third hand' during my years of modelling - plus, a prehensile tail is of some assistance!

 

Why the need for the extra appendages? Because the frames are made of three pieces (the wheels being in outside bearings), and holding all three together for soldering without the wheels escaping as the structure collapses needs more than two hands! 

 

Significantly, DJH kits produced for tender locos after the A1 had sub-frames for holding the tender wheels. 

 

 

Edited yesterday at 16:04 by Tony Wright
typo error

[Clive Mortimore]

Helical gears. The gear wheel has its teeth cut at an angle. The angle matches the helix of the gear worm. It improves the efficiency of the worm and gear wheel in not having to over come the square cut corners of the gears as found on most model trains. It is these square cut corners that cause most the noise as the two surfaces rub up against each other. The worm doesn't wear out as fast again as it its not making unnecessary contact with the square corners of the gear wheel.

Edited yesterday at 12:02 by Clive Mortimore

[polybear]

3 hours ago, Captain Kernow said:

No, I haven't and I didn't realise that they produced them. I would certainly be interested in putting one in a future loco build, but is anyone aware of whether they are currently available, given the fact that Mark Arscott is sadly unwell?

 

The Markits website still says no orders are being accepted

[1471SirFrederickBanbury]

I will just add that bevel Herringbone gears are ideal, but evidently hard to make without the right gear shaper. Thats all for now. 

[1471SirFrederickBanbury]

16 hours ago, t-b-g said:

 

Having seen the Sid Stubbs gearboxes at first hand, it would absolutely impossible to improve on them in terms of the quality of construction and the smoothness of the drive. They have no detectable backlash and they run absolutely smoothly in either direction. Running them backwards, by turning the wheels, requires a small amount of pressure to turn the worm wheel but running them the correct way there is no resistance that can be felt by hand. There will obviously be some but it so small as to be of no consequence.

 

I can understand why the gears illustrated would be more efficient but trying to make them would be beyond most people. The ones illustrated look like 3D printed examples. If anybody can make ones that work as smoothly as the Sid Stubbs gears without using CAD/CNC techniques, I would be hugely impressed.

 

You clearly have some in depth knowledge of engineering matters, far more than I do. I would recommend the article by Sid in MRJ if you haven't seen it. It would need some engineering background to fully appreciate it.

I'm impressed immensely (and immensely jealous) of such perfect performance!  I'm planning on trying to recreate/improve by using a fast motor with a heavy flywheel, high ratio (preferably herringbone) bevel gearbox and a Bendix clutch on the axle to try to get the smoothest starts, slowest sustained speeds, and best coasting possible.

 

  The theory behind my idea is that due to fast motors having a much greater rpm range, that if I gear them down significantly, the flywheel should allow the motors to coast smoothly at a decently low rpm, which will be reduced down to an impossibly slow crawl with super smooth acceleration.  With the Bendix clutch, the threaded collar attached to the final drive gear will be floating at the start, which means even if the motor doesn't start perfectly smoothly, the rpm will be able to stabilise, and the clutch will allow it to slowly take the load of moving the train, slightly slipping initially at any torque jumps that occur.  The flywheel will also be acting to keep things smooth as it slowly puts its energy into the slipping clutch, with the momentum of the loco acting to prevent jumpiness at this stage.  Once all the slack is taken up and the the loco starts crawling faster, the massive torque generated from the heavily geared down motor and flywheel keeps everything right as the loco slowly accelerates.  Once the train is coasting, regulator is cut down, and the clutch backs off, cutting off any drag from the gears and motor and allowing the train to go on for quite the long while.  Does this sound good to you?  I definitely want to experiment to find what's ideal, but in my head this sounds almost perfect!

 

the best part of the clutch that I though was that I can use the internal movement to actuate the reach rod, and with some surprisingly compact use of springs and an extremely small centrifugal governor, I figure that I could quite realistically simulate the appropriate valve gear cut-off setting at most speeds, with the radius bar coming back to near the centre more as the speed increases.  I can't promise that It'll work first time, but its decently straight forward in my head, which doesn't say much!

[Chuffer Davies]

Have you heard of Dynadrive Rohan? It was developed in the 1980’s (?) and sounds very much like what you are describing.  I have only ever seen one model fitted with it and it was very impressive indeed.  It required a lot of space and for a steam outline model typically needed the motor and flywheel installed in the tender. 
Regards,

Frank

[t-b-g]

2 hours ago, 1471SirFrederickBanbury said:

I'm impressed immensely (and immensely jealous) of such perfect performance!  I'm planning on trying to recreate/improve by using a fast motor with a heavy flywheel, high ratio (preferably herringbone) bevel gearbox and a Bendix clutch on the axle to try to get the smoothest starts, slowest sustained speeds, and best coasting possible.

 

  The theory behind my idea is that due to fast motors having a much greater rpm range, that if I gear them down significantly, the flywheel should allow the motors to coast smoothly at a decently low rpm, which will be reduced down to an impossibly slow crawl with super smooth acceleration.  With the Bendix clutch, the threaded collar attached to the final drive gear will be floating at the start, which means even if the motor doesn't start perfectly smoothly, the rpm will be able to stabilise, and the clutch will allow it to slowly take the load of moving the train, slightly slipping initially at any torque jumps that occur.  The flywheel will also be acting to keep things smooth as it slowly puts its energy into the slipping clutch, with the momentum of the loco acting to prevent jumpiness at this stage.  Once all the slack is taken up and the the loco starts crawling faster, the massive torque generated from the heavily geared down motor and flywheel keeps everything right as the loco slowly accelerates.  Once the train is coasting, regulator is cut down, and the clutch backs off, cutting off any drag from the gears and motor and allowing the train to go on for quite the long while.  Does this sound good to you?  I definitely want to experiment to find what's ideal, but in my head this sounds almost perfect!

 

the best part of the clutch that I though was that I can use the internal movement to actuate the reach rod, and with some surprisingly compact use of springs and an extremely small centrifugal governor, I figure that I could quite realistically simulate the appropriate valve gear cut-off setting at most speeds, with the radius bar coming back to near the centre more as the speed increases.  I can't promise that It'll work first time, but its decently straight forward in my head, which doesn't say much!

 

As Frank says, it does sound a lot like the commercial Dynadrive system, which came and went a few years ago. I saw a couple of locos fitted with it and it was very impressive but almost impossible to stop accurately. If you wanted to stop on an uncoupling magnet, it could take ages shuffling forwards and backwards to get it to stop in just the right place.

 

 

Speaking of flywheels, I posted this a while back but this is a photo of a mechanism built by the late Alex Jackson, very likely in the late 1940s. Entirely scratchbuilt, including the 24v DC motor, wheels and gears, it includes a loose connection between the flywheel and motor, so if you change direction the motor moves before it takes up the flywheel. The flywheel has bearing supports front and back The gears are home made but obviously not in an enclosed box. The connection from motor to gears is flexible and is, in effect, a coil spring. So again, the motor moves first, then the worm wheel a tiny amount later.

 

I have seen a demonstration of this type of mechanism and by turning off the power with the loco doing around a scale 40mph, the loco ran on around 2 feet by the action of the flywheel. All metal wheels and split frames are incorporated too.

 

The Sid Stubbs home made gear boxes appear in one of the shots too, although you can't see what is inside! One was produced for O Gauge too. These were for demonstration purposes.

 

 

I really enjoy seeing people trying out different methods and I look forward to hearing how you get on with your clutch. Maybe it works superbly or maybe the results don't justify the work involved. It is only by people experimenting and trying things that we move forwards. That applies to life in general just as much as it does to model railways. I am always happy to try new things. Just doing the same old tasks the same old way is just a good way for me to get into a bit of a rut.

[lezz01]

Yep that sounds exactly like a Dynadrive Rohan. They were very good but very difficult to stop. It was a series of big flywheels each one driving the next through a clutch. It suffered from two main problems. The first was the stopping issue and the second was it's size and weight. I first saw it demoed at Scaleforum and it would just about fit in a Class 40. 

To add insult to injury it was pricey as well and the weight issue didn't help with the stopping issue as the loco could plough through the buffers and keep going. Don't get me wrong as a concept if was fine but over complicated and you could get the same results by having a second free running motor with a flywheel wired in series with the traction motor for a fraction of the price. It was more controllable to boot. The advent of DCC put an end to it completely.

Regards Lez.   

[John Isherwood]

25 minutes ago, lezz01 said:

... you could get the same results by having a second free running motor with a flywheel wired in series with the traction motor for a fraction of the price. It was more controllable to boot.

 

...... and, in pre-DCC sound days, the free-running motor gave a 'sort-of' simulation of engine run-up.

 

I tried adding a simple free-running motor in a Tri-ang-Hornby Brush Type 3, without the flywheel, and running was certainly smoother.

 

Mind you, this was also a 3-rail conversion, with a HD centre rail collector bolted through the fixing rivet of the unpowered bogie!

 

Many, many eons ago ....

 

John Isherwood.