Electric Traction Engine

[Ron LadenParticipant @ronladen17547]

Managed to pick up some mild steel blanks yesterday, local and even better "free"..

Machined to size and shape this morning, just a 1/2 inch rad to put on the top front corner but will do that by hand.

I went with 3mm sheet in the end, scale wise that is 7/8 of an inch, although I,m not building a scale model I would like to try and keep things looking realistic. I dont know the side plate thickness on a full size engine (varies I suppose) but I guessed at 1 inch, I could be way off but hopefully not.

[Paul KempParticipant @paulkemp46892]

Ron,

Not that I have made a habit of measuring them but most full size horn plates I would say dependent on the size and breed of engine range from 3/8" to a max of 3/4". Where they are normally an extension of the outer firebox sides the thickness will be governed by the thickness of the boiler plate. They are remember, stiffened up by fairly heavy castings bolted to them that carry the crank and second and sometimes third shaft bearings. They are also stiffened up by the front plate and spectacle plates fixed between them, forming a 'box' over the firebox / boiler. That said 3mm I would say is a good choice for yours. The phrase you can't scale nature holds true here, where an exact scale thickness in smaller sizes would make things a little 'floppy' and perhaps not too resiliant to out of scale forces!

Paul.

[Neil WyattModerator @neilwyatt]

I'm surprised your tube was that far out. When I made my scope I took a tidying up cut on the outer diameter, but it was only a tiny scrape to give a good finish.

Neil

[JasonBModerator @jasonb]

Must have been at the bottom of the Posties bag and got squashed.

The Minnie is quite chunky so when scaled up you can get some oversize sections.

[Ron LadenParticipant @ronladen17547]

Posted by Neil Wyatt on 13/11/2018 18:52:41:

I'm surprised your tube was that far out. When I made my scope I took a tidying up cut on the outer diameter, but it was only a tiny scrape to give a good finish.

Neil

Hi Neil, must admit I was surprised it was as far out as it was but 101.3 to 102.8 at one end and 101.4 to 102.9 at the other and that is over 280mm length. I probably got the first or last bit out of the die plus it probably came in from Russia, a lot of aluminium extrusion comes from there.

[Ron LadenParticipant @ronladen17547]

Gradually putting together a material shopping list, I will be machining the cylinder block from solid and was thinking of what would be a good material for this. When using castings I dont know what they are made from, bronze, cast iron..? Of course I dont have to consider the cylinder in quite the same way as it wont be live steam and will be working in reverse… i.e. the piston will be driven by the connecting rod. In operation it will look the same but the drive will be from the drive motor further down the gear train.

I was thinking of using bronze, but any other thoughts would be helpful.

Ron

Edited By Ron Laden on 13/11/2018 21:15:30

[Anonymous]

Posted by Ron Laden on 13/11/2018 09:23:26:

I went with 3mm sheet in the end, scale wise that is 7/8 of an inch, although I,m not building a scale model I would like to try and keep things looking realistic. I dont know the side plate thickness on a full size engine (varies I suppose) but I guessed at 1 inch, I could be way off but hopefully not.

More like 3/8" in full size, the same as the boiler plate thickness, give or take. In full size the hornplates are extensions of the boiler, not separate plates as in most models.

Andrew

[Paul KempParticipant @paulkemp46892]

Posted by Ron Laden on 13/11/2018 20:57:52:

Gradually putting together a material shopping list, I will be machining the cylinder block from solid and was thinking of what would be a good material for this. When using castings I dont know what they are made from, bronze, cast iron..? Of course I dont have to consider the cylinder in quite the same way as it wont be live steam and will be working in reverse… i.e. the piston will be driven by the connecting rod. In operation it will look the same but the drive will be from the drive motor further down the gear train.

I was thinking of using bronze, but any other thoughts would be helpful.

Ron

Edited By Ron Laden on 13/11/2018 21:15:30

Ron,

Full size would be cast iron. In your case where you don't need to consider corrosion bronze would be an expensive way to do it! Unless you are planning to use the puff from a driven piston for a smoke effect or something why bother with a piston at all? You can just have the piston rod supported from the cross head and running in a brass gland (same with valve rod) and the 'cylinder' can be aluminium, steel or even wood! Whatever is easiest to machine and is cost effective.

Paul.

[JasonBModerator @jasonb]

I would also think about how you are going to make the cylinder, will it be from one solid lump or you could save a lot of material by having the curved "flange" that mates to the boiler as a separate part. If you go for two parts think about how to joint as solder will need certain materials but screw and glue won't restrict you. I'd most likely go with aluminium two part construction especially if you can find the next size up pipe tp fit over the boiler.

As to boiler thicknesses I've just had a quick look at Gilbert's and the various original boiler drawings in there range from 3/8 for a small Tasker tractor upto 5/8 for a Fowler ploughing engine on the outer plates but all have 3/8" firebox sides.

[Ron LadenParticipant @ronladen17547]

Thanks guys,

Paul, of course you are correct I dont need a piston. I was thinking I would need one to keep it all running true but of course with the rod running in a gland and supported from the cross head it will be fine. I think aluminium would be a good choice as it machines well and not too costly.

Jason, I was thinking of having a go at machining the cylinder from solid but I can see the merits of a two piece assembly. I havnt looked for any next size tube but if I cant find any I do know someone who could roll me a piece. I wouldnt need a full tube of course, just a blank to the correct radius which I could cut the part from. Could also cut out a saddle for the chimney base.

Thanks again guys.

A picture below of the horn plates offered up the right way around, I was just testing with the previous photo..

[Ron LadenParticipant @ronladen17547]

Taken the dimensions of the 1 inch Minnie cylinder block (less the saddle) and increasing it to my scale (1.625 inch to the foot) I should be able to get it out of a 100mm x 80mm dia 6082 off cut I have, so thats a bonus.

Working on finalising the gear train and the best place to introduce the motor drive. The motor will be mounted in the boiler/firebox area, I have considered taking the drive up through the top plate and connecting to the second shaft but its not that simple. So I think I will go with the mounting the motor to the offside side plate driving a 20 tooth which connects with the 50 tooth on the 3rd shaft. This shouldnt look too bad, it is an extra gear and it would have been good to drive the 20 tooth on the 2nd shaft but the motor is 90mm diameter so it has to be mounted quite well down on the side plate and would mean more gears to make the connection.

Ron

[Ron LadenParticipant @ronladen17547]

Out of interest and something I have often puzzled over, why chain steering on traction engines..? Obviously it works but it hardly seems a positive means of steering. When you consider the engineering that goes into an engine the means of steering seems a bit crude, wonder why they didnt go with say a geared system with push rods etc or something similar. Maybe there is a good engineering reason for chain steering, I,m sure you guys who know the history of and the ins and outs of traction engines will know.

Ron

[Ron LadenParticipant @ronladen17547]

Having considered the gearing and the best way forward with the drive, the basic sketch below shows what I am planning. Its not set in stone but I think it would work out ok, I have copied the Minnie gear ratios and most of the drive is mounted in a similar position. The third shaft however is not as per Minnie but that comes about mainly because I am using two MOD sizes plus the increase in scale. The thing I considered as a starting point was the positions of the crankshaft, second shaft and axle and then fitting the gear train between them.

I am going with a 10T gear on the motor driving the 80T final drive gear, a ratio of 8/1 should provide some reasonable torque with the motor I plan on using and sensible speed.

Ron

Edited By Ron Laden on 16/11/2018 13:36:30

[Anonymous]

Posted by Ron Laden on 15/11/2018 21:06:50:

Out of interest and something I have often puzzled over, why chain steering on traction engines..? Obviously it works but it hardly seems a positive means of steering. When you consider the engineering that goes into an engine the means of steering seems a bit crude, wonder why they didnt go with say a geared system with push rods etc or something similar. Maybe there is a good engineering reason for chain steering,

Cost and practicality. Chain is cheap compared to gears and pushrods. The chain worm gear is relatively lightly loaded compared to a direct gear drive. And for agricultural engines in particular the front axle can be anything but horizontal; a chain copes with that no problem.

Some traction engines, and especially rollers, did use geared steering, but not many.

Andrew

[Ron LadenParticipant @ronladen17547]

Thanks Andrew, I did think cost and simplicity would come into it and it makes sense when you consider travelling over rough ground.

Ron

[Ron LadenParticipant @ronladen17547]

I am not geared up (excuse the pun) to making my own gears so I have decided to buy them in, they will all need modifying so I can at least know I have put some effort into them (why do I always feel guilty at buying parts in).

At the MOD sizes I am going with all the gears will need reducing in thickness as they are all too wide across the teeth. Some of them will also need hubs removing but some I can get without hubs.

A full set of 9 off EN8 gears I can get for £105 which I dont think is too bad at all, its the 80 tooth that bumps it up, as that is half the cost of the set. I could save about £20 if I split the set up and buy from different suppliers, but I just feel it maybe safer to get them all from one source.

Ron

[Paul KempParticipant @paulkemp46892]

Ron,

I think a little while back you were considering getting a rotary table? That being the case you could get one with a dividing attachment and cut your own gears. However financially and in terms of time expended, buying your gears would be the cheaper and quicker option. Time you have bought said rotary table with dividing discs, found the std discs may not cover the divisions you need so made another custom disc, purchased the required gear cutters and then bought the material for the blanks, turned them up and cut the teeth……….. You will be quite a bit older and poorer by more than £105! It all depends on your outlook really.

I have just cut the full set of gears for my half size traction engine, took me the best part of 3m of Saturday's and Thursday night's, despite borrowing the cutters I very much doubt I saved much money wise and it took a lot of time. I did it purely because I can and wanted to be able to say that apart from the professionally built boiler (too complicated in terms of certification for me to do) and actually pouring the castings I want to be able to say "I built that". There is not too much to cutting gears in terms of complication but it's a lot of handle winding and general effort! If I were to build another (which I doubt I will!) I doubt I would cut the gears again myself!

Paul.

[not done it yetParticipant @notdoneityet]

Paul,

Cutting gears is a doddle with power feeds. Setting up for gear cutting is the most fiddly part.

[Ron LadenParticipant @ronladen17547]

Hi Paul,

As I mentioned in my post I do tend to get a guilty feeling when I buy parts in, I dont know why though and as you suggest its depends on how you look at it. If I were building a scale engine (which I doubt I actually could) then I would look at it differently. I would want to be able to say "I built that" knowing that apart from say a few parts which for whatever reason I could not do, all of the rest I had made and built into the engine.

Of course I am not building a scale engine, its freelance and to be honest most of it will be worked out as I go along. I do want to make as much of the engine as I possibly can and I did give the gears some thought but in the end decided to buy them in.

Paul, you are building a "half size" traction engine..? Wow, I am impressed, that is some undertaking, how long have you been working on it and what stage are you at..?

Ron

[Anonymous]

Posted by not done it yet on 17/11/2018 20:33:37:

Cutting gears is a doddle with power feeds.

Not much use if the gear is too big to go under the arbor, and you don't have power feed on the knee.

Andrew

[Ron LadenParticipant @ronladen17547]

Andrew, what size engine are you building, thats no small gear wheel..?

Ron

[Anonymous]

Posted by Ron Laden on 17/11/2018 21:19:59:

Andrew, what size engine are you building, thats no small gear wheel..?

I'm building two 4" scale engines, so one third full size. The gear shown is one of the 5DP final drive gears, the OD is 14.8 inches. Each cut was 25 turns of handle up, and another 25 turns down. So a lot of handle turning. Still it gets the old ticker going, and it's more fun than jogging.

Andrew

[Paul KempParticipant @paulkemp46892]

Ron,

It's a relatively small half size, a Savage, it's around 8' long and the completed weight will be in the order of 1000kg. I have been on it 2 years now and I am about 2/3 completed, hoping to light a fire in it later next year.

NDIY, well the next set of gears I will send your way then. The largest of the recent batch was 19" diameter, 4 DP. My set up for three of them was very similar to that Andrew shows, horizontal mill with no power feed to the knee. Nothing fiddly about setting it up, clamped down concentric on RT, put the right plate on, set the sector arms, centred it on the cutter, touched off, put on full depth of tooth space and away you go! About an hour to set up, 76 tooth spaces 0.540" deep and roughly as wide, gear is 1" thick – so a lot of metal to plough out in one go, avenged about 17mins per cut.

Paul.

[Ron LadenParticipant @ronladen17547]

Paul/Andrew, I am impressed to say the least, engines of that size is some commitment, great stuff.

Paul, half scale and 2/3 complete in 2 years, thats some progress isnt it I thought it would take much longer to be that far on.

Andrew, why two engines ? are you building the second one for someone else, sorry I am just been nosey.

Ron

Edited By Ron Laden on 18/11/2018 08:35:11

[Ron LadenParticipant @ronladen17547]

This morning in the workshop I had a thought which could be a daft one so feel free to jump in.

I have an offcut of brass T section 25mm x 25mm x 3mm and I wondered if T section could be used to make up the wheel rims. At my scale the central leg of the T would need milling back to give a 10mm deep web. It would need to have 2 T sections connected together side by side to give a 50mm wide wheel. The problem I see, would it be possible to form the T into a 9 inch diameter rim without the web or the T distorting or buckling..?

I thought of a jig made up of two discs sandwiched together with 3mm plus a bit spacers to produce a slot around the circumference for the web to sit in. I wondered if I used some heat and clamped the section around the jig as I go would it work..? If it did then the two sections could be soldered together around the circumference making up the rim, the webs would be at the correct spacing, though they would be a bit undersize thickness wise but I could live with that. The same T section is available in aluminium but I thought that brass maybe better suited though the brass is seriously more expensive, aluminium is more attractive price wise.

I cant turn the rims on the mini-lathe they are to big so I have been trying to think up other ways of producing the rims.

A daft idea or a non starter..?

Ron

 

Edited By Ron Laden on 18/11/2018 09:54:23

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