Miniature Traction Engine

[Nigel Taylor]

Just stumbled across this thread, quite ridiculous what somebody can achieve with enough skill, patience and determination.
Not just the model making but all the theoretical analysis on the boiler design too, just stunning.
I would be interested to know what your actual job is assuming it is something to do with the model making? I'm curious because if I was to create something like this project I would want to be paid about £20k for it and I'm pretty sure nobody is going to pay that, even though it's probably worth that much in ingenuity and hours. Or maybe somebody does pay that, I have no idea. Just curious how this stuff works commercially. You deserve every bit of good fortune you get though! Amazing.
Martin

Hello Martin,
Thanks for the kind words. Until very recently I have headed up a battery research and development team. Now I have more time to spend on model making which is great. I've been model making for a long time having started using a lathe when I was 11. However, my background is a degree in physics and from this I worked in acoustics for many years before designing a number of hybrid concept cars. Hence moving to battery research and design. So, I'm a self taught model engineer and I just really like understanding how things work and how to make them.

I haven't added up the hours that have gone into this model, but far beyond anything I could charge for. I will develop a set of plans for the engine as I think others will want to make it. Although I still have a lot of parts to design and make before I finish. Including a working differential that is being designed in my head at the moment.
Thanks, Nigel

 

[Molynoox]

Brilliant, thank you. Good luck with the differential that won't be easy but I'm sure you will enjoy it. Looking forward seeing it all finished.
Martin

 

[Nigel Taylor]

I've now got the door hinge made and the brass plaques bolted to the door. Moving forward again after deciding the flat smokebox door wasn't good enough.



The Burrell door now has the correct curvature, the brass plaques are bolted to the door and the hinge is in place. Now I just need to add the beam to the smokebox so that this door can be bolted shut.

 

[Nigel Taylor]

I've now made the Burrell door handles and the locking system, this now all works at 1/20th scale.

This hopefully shows the basic locking system.

The Burrell door lock is a T-head bolt with flat sides on the threaded section. This bolt goes through the door from the back, a handle with a slot then goes on allowing the bolt to be rotated. A second handle with a threaded not then allows the bolt to be pulled up tight.

In the smokebox a beam goes across the diameter of the opening and has a slot in it to allow the bolt head to go through. Then the bolt is rotated and hence the T-head gets a purchase on the beam.

The handles were made as one part based on them being so small and then I split them into two parts later.

Still lots to do

 

[Nigel Taylor]

Also, just been working out how to get to 10:1 as an overall ratio and where the layshaft can go.

then some calculations of the options (using excel)

and I think I have a sensible result

 

[J-G]

...and I think I have a sensible result

Well I'm sorry Nigel, I don't think you have - on many counts

First - you haven't achieved a 10:1 - it's close at the real figure of 10.14634 but 10:1 is acheivable.
Second - you have a 41T gear in the train which is a prime number and therefore complex to manufacture needing an accurate progression of 8.780487805° between each tooth. I don't have a solution in my gear-hobber tables for 41T - but I have made one by engraving a sheet of Tufnol on my CNC machine.
You also have a 117T and, whilst not prime, is odd with only 4 factors, needing a progression of 3.076923077° and 29T needing 12.4137931°. All OK if you have dividing plates with 29, 41 & 117 holes but again I don't have a solution for either of these; I can get 29.0013986

Now I must say that I think that you have done a fantastic job on this engine so I'm not decrying your efforts in any way, but there is a solution to your 10:1 which is a much better 'fit'.

I have had to work from the photo you posted and used that to 'scale' my drawing. I have to assume that the 67.575 measurement is sacrosanct and I can only guess at the absolute centres of the two bearings from your low-res image so you will see from my drawing that I'm out on that by 0.0183mm which will have some bearing upon the dimensions for the location of the lay shaft but I doubt that they will be too significant.

This solution uses tooth counts which are easily manufactured - 25, 48, 100 & 120. Incidentally, I have used a 'clearance' - between meshing gears - of 0.1mm so the physical properties of the gears is :

The 'normal' terms used to specify gear dimentions are Pitch Circle Diameter (PCD) and Outside Diameter (OD) rather than 'radius' or 'Tip diameter'. 'Centre Distance' is of course of prime importance.



I would presume that the ideal location for the layshaft would be in line with the 120T gear - which would be 90° to the bottom edge. My calculations put it at 89.48079° and to make that any more meaningful I would need very accurate information as to the precise distance between the two bearings measured parallel to the bottom edge of the Brass plate - this is the 23.2122 measurment in my drawing which is a simple scale measurment of your photo so subject to all manner of possible errors. Changing the clearance from 0.1 to 0.2 would have a significant effect upon that angle. It may well be inconsequential but when designing clocks (or any gear train) I try to stick to easily achieved 'in-line' or 90° locations wherever possible.

 

[J-G]

I've just noticed that you may not be able to use a 120T gear since that may be larger than the wheel, which would mean that it would foul the ground !

Fortunately there is another combination that will still give you 10:1 exactly, still be easier to manufacture, NOT foul the ground and still have a total centre distance greater than the 67.575 dimension.

I've added the dimension from the top bearing to the lay shaft on this drawing as well.

Here are the ammended gear dimensions.


I do hope that there are no other 'constraints' that I've missed.

 

[Nigel Taylor]

Just made the gears for the drive wheels, made 3 off, not quite sure why an extra....

These are 117 teeth 0.5 module. I reamed a 10mm hole in the centre, intention is to make a hub that runs on the axle and is bolted to the wheel. This 10mm hole mounts onto a very close fitting mandrel when machining the outer diameter and cutting the teeth.

I apologise to the clock makers for my very strange number of teeth. I have been trying to get something that doesn't repeat - or at least not very often.

 

[Nigel Taylor]

Well I'm sorry Nigel, I don't think you have - on many counts

First - you haven't achieved a 10:1 - it's close at the real figure of 10.14634 but 10:1 is acheivable.
Second - you have a 41T gear in the train which is a prime number and therefore complex to manufacture needing an accurate progression of 8.780487805° between each tooth. I don't have a solution in my gear-hobber tables for 41T - but I have made one by engraving a sheet of Tufnol on my CNC machine.
You also have a 117T and, whilst not prime, is odd with only 4 factors, needing a progression of 3.076923077° and 29T needing 12.4137931°. All OK if you have dividing plates with 29, 41 & 117 holes but again I don't have a solution for either of these; I can get 29.0013986

Now I must say that I think that you have done a fantastic job on this engine so I'm not decrying your efforts in any way, but there is a solution to your 10:1 which is a much better 'fit'.

I have had to work from the photo you posted and used that to 'scale' my drawing. I have to assume that the 67.575 measurement is sacrosanct and I can only guess at the absolute centres of the two bearings from your low-res image so you will see from my drawing that I'm out on that by 0.0183mm which will have some bearing upon the dimensions for the location of the lay shaft but I doubt that they will be too significant.
View attachment 129983
This solution uses tooth counts which are easily manufactured - 25, 48, 100 & 120. Incidentally, I have used a 'clearance' - between meshing gears - of 0.1mm so the physical properties of the gears is :
View attachment 129984The 'normal' terms used to specify gear dimentions are Pitch Circle Diameter (PCD) and Outside Diameter (OD) rather than 'radius' or 'Tip diameter'. 'Centre Distance' is of course of prime importance.



I would presume that the ideal location for the layshaft would be in line with the 120T gear - which would be 90° to the bottom edge. My calculations put it at 89.48079° and to make that any more meaningful I would need very accurate information as to the precise distance between the two bearings measured parallel to the bottom edge of the Brass plate - this is the 23.2122 measurment in my drawing which is a simple scale measurment of your photo so subject to all manner of possible errors. Changing the clearance from 0.1 to 0.2 would have a significant effect upon that angle. It may well be inconsequential but when designing clocks (or any gear train) I try to stick to easily achieved 'in-line' or 90° locations wherever possible.

Thanks J-G, you have put a lot of effort into these calculations and much appreciated. The 10:1 is not an absolute as I would prefer odd numbers so that the gear teeth don't repeat. I didn't put this as a constraint as it was just something that didn't have to happen.

Apologies for my description of tip radius and centre distance - I will change these.

I think the inline might be nicer in some ways, but pulling the shaft closer to the firebox face will help with access to the door.

Thanks, much appreciated, Nigel

 

[Nigel Taylor]

117 divisions is 3.0769230769 degrees and I'm using a rotary table with a worm drive that gives 4 degrees per rotation. This then has dividing plates and for this I selected 39 hole plate and then used a step of of per tooth. Hence 30/39 of 4 degrees.

Hope that makes sense, best regards, Nigel

 

[Nigel Taylor]

for 41 teeth I will use a 41 division plate and then each step is 2 rotations + 8/41 this then gives a step of 8.7804878049 degrees

 

[J-G]

It seems that the only 'constraint' that I had not taken account of is the fact that you 'wanted' odd numbers

I'm sure there is a sensible reason for that but it's way beyond my comprehension. It just seems to go against all my engineering training and logic but it is gratifying to see that you have the means to create the 'odd' gears that you have perfectly logically selected.

No need for an apology regarding the 'technical' descriptions - I've spent many years leaning 'engineer's speak' and am naturally a pedant - - you should use whatever descriptions that you find work for you, even I eventually fathomed what you meant!

It so happened that I had some time on my hands today since a choir rehearsal had been cancelled so applying myself to interesting calculations was a welcome distraction.

 

[Nigel Taylor]

It seems that the only 'constraint' that I had not taken account of is the fact that you 'wanted' odd numbers

I'm sure there is a sensible reason for that but it's way beyond my comprehension. It just seems to go against all my engineering training and logic but it is gratifying to see that you have the means to create the 'odd' gears that you have perfectly logically selected.

No need for an apology regarding the 'technical' descriptions - I've spent many years leaning 'engineer's speak' and am naturally a pedant - - you should use whatever descriptions that you find work for you, even I eventually fathomed what you meant!

It so happened that I had some time on my hands today since a choir rehearsal had been cancelled so applying myself to interesting calculations was a welcome distraction.

The odd was just to ensure no repeat as it's for a gearbox. No real need as it will not do much work. The dividing head is a Warco HV4 rotary table with dividing plates on the input. Not as good as a much larger dividing plate that I can fit on the back of the lathe head to do more precise divisions. However, that is more limited in numbers.

Had a look at your website, some great items on there. Thanks for the time doing the calcs, it was good as it made me double check the numbers as I must admit I thought I might have rounded off the calculation to get to 117.

 

[J-G]

Glad you consider my input useful - and thanks for the kind comments regarding some past work.

Like any 'tool' a dividing head is only as good as the operator. As long as you always work in the same direction and not go past the hole required and then just turn back you should be OK.

Gearing ratios do need careful assessment and of course they are resticted to integer numbers, so often I've wanted a ½ or ¼ tooth !

Rather than intrude further into your thread, I'll send you a PM.

 

[Fergie 307]

After a lot of help from a fellow steam model engineer I've managed to make and silver solder the boiler end plate stiffeners in place.

I think I'm a gluten for punishment pursuing the silver soldering in a kiln. The Easy Flo 24 did not flow as well as some of the lower temperature silver solders.

Never tried doing this in a kiln, but for normal work they do a particular flux for when you need it to work over a long period of heating. Can't recall the name now without going to the shop and looking at the jar. Might be worth trying though. Regular flux only tends to work for quite a short time, sustained high temperatures cause it to burn.

 

[Fergie 307]

Thanks, I try to share as much as I can, sometimes though I think people will be bored watching me make something.

Never boring, keep them coming loving every minute of it !

 

[Fergie 307]

An image of saddle silver soldered to the boiler.

My test coupons and checking out different silver solder masking techniques paid off.

The engine reassembled and I think it's looking good.

The silver solder coming out from the edge is minimal and yet it is complete all the way round. This will be covered by an insulation sheet and a brass sheet wrap anyway.

lovely joint, was that masked with the graphite, or some other method?

 

[Nigel Taylor]

lovely joint, was that masked with the graphite, or some other method?

thanks, yes, used a graphite pencil and created a mask with it - this works rather well and is very easy to do and to clean up afterwards

 

[SamG340]

Until very recently I have headed up a battery research and development team.

Hi Nigel fantastic work, amazing really. Not sure if this has already been asked but are you making a working model? Is it going to be a coal burner ?

Also sorry to go off topic here

Right now as I'm sure you know batteries are too heavy, take too long to charge up and don't last long enough , even LI are pretty naff when it comes down to it. I was wondering if there's anything interesting in the pipeline for batteries in the near future?

 

[Nigel Taylor]

Hi Nigel fantastic work, amazing really. Not sure if this has already been asked but are you making a working model? Is it going to be a coal burner ?

Also sorry to go off topic here

Right now as I'm sure you know batteries are too heavy, take too long to charge up and don't last long enough , even LI are pretty naff when it comes down to it. I was wondering if there's anything interesting in the pipeline for batteries in the near future?

Hi Sam, it's a working model. Coal maybe, although gas might be easier. I would like to run it on coal, if just once. But the whole thing is quite small and losses don't scale well.

Batteries, there are no significant changes coming. Everybody is working to reduce the package overheads, this will help. The main drive though has been on cost to bring it comparable to IC. The other axis of the problem is energy consumption: smaller and better aero, improved motor efficiency (peak efficiency is good and around 94%, but we don't drive there often), silicon Carbide inverters will migrate from the exotic down to normal cars. So, don't expect a step change, but improvements on all fronts. Plus buy the smaller sized vehicle, not 4x4 monsters that will always be power hungry.