Electric Traction Engine

[Ron LadenParticipant @ronladen17547]

Thanks Paul, thats helpful.

Ron

[JasonBModerator @jasonb]

Generally the smaller the model engine gets the faster the crank has to spin to get a usable road speed which means you have to spin it at well over full size revs.

If you went with the suggested 300rpm then you would be moving at about 0.5mph in low and 0.8mph in high assuming 9" rear wheels.

[Ron LadenParticipant @ronladen17547]

Thanks Jason, at the scale I am using 1.625 the rear wheels will be 9.75 inches, if my sums are correct that equates to 189 rpm at the wheel for 5mph. In high gear the crank would be fair whizzing around but I planned on using Minnie gearing and thats how it would come out.

The metal and boring head have arrived so about to start cutting metal at long last. This morning I was given an offer you cant refuse…but I did. I called in at a local machine shop, I have known them for years from my working days. They let me rummage through their scrap bins and this morning I was looking for some packing pieces for the mill table. Got talking to the owner and he was asking about the mill and the engine etc, I told him that I had got a boring head for cutting the 4 inch hole and said I would start with chain drilling the bulk of it out. "Oh you dont want to mess about like that" he said. "Bring it in and I will put it up on one of the CNC,s and do it while you wait, it will take no time"

When I told him thats kind and thanks but I would rather do it myself for the experience etc I dont think he could quite understand.

Was I tempted, you bet I was but I resisted.

Ron

[Mike PooleParticipant @mikepoole82104]

It’s a shame that speed doesn’t scale, it always seems that train sets go much too fast but if you did apply the same scale factor to speed it would seem unreasonably slow so what shall we do?

[Ron LadenParticipant @ronladen17547]

Your quite right Mike, I have a N gauge 1/148 model railway layout and on occasion I have asked some family and friends to set a train running not too fast but what they consider 30 mph and each time they set it way too fast. When I tell them that the speed they set is more like 60-70mph or more they never believe it, it must be a visual thing.

[Anonymous]

Posted by Ron Laden on 31/10/2018 13:03:12:

Thanks Jason, at the scale I am using 1.625 the rear wheels will be 9.75 inches, if my sums are correct that equates to 189 rpm at the wheel for 5mph……

I think that's wrong. The circumference of a wheel 9.75" is (times pi) 30.631".

There are 63360 inches in a mile (*) so 5 miles is 316800 inches, in a hour for 5mph, which is also equal to 5280 inches per minute (divide by 60). Divide 5280 by 30.631 to get the rpm, equals 172.37rpm.

Andrew

(*) I knew that without looking it up as it is the scale of the old OS 1" to 1 mile maps.

Edited By Andrew Johnston on 31/10/2018 19:54:15

[Ron LadenParticipant @ronladen17547]

Quite right Andrew, I looked at my scribblings and I had written 5800 per mile instead of 5280 hence my 189.

Eh I was only 17 rpm out, I know, I know, every revolution counts.

Ron

[JasonBModerator @jasonb]

Good job you got that right as it brings the crank revs down to a more sedate 1724rpm

Though all bets are off if you decide to fit rubbers!

Edited By JasonB on 31/10/2018 20:29:26

[Ron LadenParticipant @ronladen17547]

Just to say I have made a start and cutting metal for the engine at long last, just facing and squaring the sides, bored the 4 inch hole yesterday which went really well, I am really enjoying the mill at the moment.

 

Edited By Ron Laden on 02/11/2018 09:43:27

[Ron LadenParticipant @ronladen17547]

I guess I probably ran a bit of a risk this morning when milling the boiler tube. The tube is a off the shelf cut length of 4 inch x 10swg 6082, 11 inches long. As to be expected its just put through a saw of some type, one end is cut nice and square but not the other, its cut at quite an angle 0-4mm across the diameter.

It obviously needed trueing up but I couldnt do it on the lathe as I have no means of supporting it, so thought I can do it on the mill. I would have liked to put a couple of clamping bars across the top but dont have any, I only have the basic clamping set at the moment. So using two of the clamps I clamped it one either end at the bottom of the tube, with the tube sitting in the T slot. It felt quite secure so I had a go, used a new Carbide Al cutter, turned the speed up and took light cuts and it worked out ok. The finish is not perfect, probably due to a slight vibration in the top of the tube but at least its true.

It was only after I finished it that I thought it probably should have been mounted better for safety,s sake… beginners eh.?

 

Edited By Ron Laden on 03/11/2018 08:55:25

[Ron LadenParticipant @ronladen17547]

The throat plate is machined, added the rebates for the top, bottom and side plates. Its ready for fixing to the boiler tube, then back on the mill to machine back the tube protrusions which will run through into the rebates.

[Ron LadenParticipant @ronladen17547]

Just wondering, would silver steel be good material for a crankshaft connecting rod, its just that the other day my CNC friend gave me some 100mm x 60mm x 8mm offcuts. Never worked with it though, does it need grinding or can you mill it ok..?

Edited By Ron Laden on 04/11/2018 19:04:22

Edited By Ron Laden on 04/11/2018 19:11:34

[Ron LadenParticipant @ronladen17547]

Silver steel obviously a daft question, sorry, all I knew was it is hard but have just read up on it and its uses and it can be difficult to machine so I will give it a miss.

Edited By Ron Laden on 05/11/2018 10:17:48

[SillyOldDufferModerator @sillyoldduffer]

Posted by Ron Laden on 05/11/2018 10:15:48:

Silver steel obviously a daft question, sorry, all I knew was it is hard but have just read up on it and its uses and it can be difficult to machine so I will give it a miss.

Edited By Ron Laden on 05/11/2018 10:17:48

Not a daft question at all. Silver steel's not hard until you heat treat it. All the silver steel and gauge plate I've used has machined OK.

The main reason for not using Silver Steel is it's more expensive than most of the alternatives, and tends to be saved for when it's needed. It's precision ground and easily hardened etc. But if you've got some spare, why not?

Dave

[Ron LadenParticipant @ronladen17547]

Thanks Dave, thats good to know and I was given six pieces of it two of which match exactly for size so a pair of parallels I thought.

Ron

[Ron LadenParticipant @ronladen17547]

Wont start another thread so thought I would ask here, I,m looking for a couple of mild steel 12 swg blanks.

The two suppliers I would normally use dont do 12swg, like most of them these days its 1mm 2mm 3mm etc. I need 2 blanks ideally cut to 188mm x 223mm, I can finish to size on the mill.

Wondered if you guys know of a supplier for 12 swg who will supply cut blanks.

Thanks Ron

[Neil WyattModerator @neilwyatt]

Is there a burning need for it to be 12 swg? If so you will probably end up paying for them to be surface ground which is probably OTT.

If you can use 3mm and make other components a touch smaller…

[Ron LadenParticipant @ronladen17547]

Posted by Neil Wyatt on 07/11/2018 21:54:07:

Is there a burning need for it to be 12 swg? If so you will probably end up paying for them to be surface ground which is probably OTT.

If you can use 3mm and make other components a touch smaller…

Hi Neil, I have found some 12swg since posting, a bit more than I wanted to pay but its not too bad. No it doesnt have to be exactly 12swg, 2.5mm would have done but I cant find any.

Ron

[SillyOldDufferModerator @sillyoldduffer]

Posted by Ron Laden on 08/11/2018 08:08:39:

Posted by Neil Wyatt on 07/11/2018 21:54:07:

Is there a burning need for it to be 12 swg? If so you will probably end up paying for them to be surface ground which is probably OTT.

If you can use 3mm and make other components a touch smaller…

Hi Neil, I have found some 12swg since posting, a bit more than I wanted to pay but its not too bad. No it doesnt have to be exactly 12swg, 2.5mm would have done but I cant find any.

Ron

 

Part of the "fun" in taking up this hobby is finding out about materials – their properties, standard sizes, and where to buy them. (Or not!)

Ron mentioned in other posts his discovery that DP Gears are more expensive than Module, and that some BA screw are hard to find. In this thread sourcing 12 gauge sheet was a problem.

The issue is that Metric has been progressively replacing Imperial stock in the UK since 1965. Since then stock availability has got ever more complicated. Many Imperial stock sizes are now 'Unobtainium' or can only be found as 'New Old Stock'. Although certain items are still made, as a whole the Imperial system is declining.

For the imperial minded hobbyist this move isn't necessarily bad news, for example industry's shift to metrication resulted in many unworn Imperial machines being dumped on the market at bargain prices. But metrication is causing trouble by progressively reducing the availability of once common stock sizes. Also – in some cases – prices rise because the market for imperial stock is shrinking and storage is expensive.

Some examples:

• Pre-war Whitworth head sizes – almost unobtainable.
• Post-war Whitworth – difficult to source – most sizes discontinued. Costly.
• SWG Magnet Wire – not difficult but easier to find metric.
• BA Screws – moderately difficult, premiums, many sizes missing, plus range of head types much reduced compared with pre-1970.
• Steel plate in gauge sizes – reduced range, higher prices. Some sizes disappeared.
• DP Gears – premium prices

Entering the hobby in 1960, it would have been unwise to go metric because most of what was available at reasonable cost was Imperial. Premium prices were paid for Metric stock and metric tools and stock were difficult to source.

It's taken a long time, but today the position has almost reversed. I suggest anyone entering the hobby today should think carefully before setting up an Imperial workshop and committing to Imperial fasteners and Imperial metal sizes. Lots of exceptions of course but I'd say the balance of advantage in the UK now lies with metric. Good reasons for not going metric:

• A workshop full of Imperial kit with matching junk box.
• A lifetime of experience working in Imperial measure. (Old dogs don't learn new tricks.)
• Building to Imperial Plans or scaling down models from Imperial prototypes
• You live in the USA or Liberia
• Many jobs can be done in either system, but mostly what you do – like restoration work  – is imperial.

I'm surprised Ron couldn't find 2.5mm steel sheet because it's a standard size. However, I may have an explanation. Although I'm lucky enough to have a local metal stockist prepared to sell small quantities I've found many mysterious gaps in what he sells. I asked the manager. Apparently he stocks to meet regular business demand and retails only from what's in the racks. He doesn't stock metal or sizes unless there's profit in it. Anything unusual is got in specially and has a hefty minimum order, perhaps a ton or more. I think such limitations are typical of small and medium sized stockists. Good news – if you need anything your local outlets don't have on the shelf then the internet is your friend!

Dave

 

 

 

 

Edited By SillyOldDuffer on 08/11/2018 11:09:22

[Ron LadenParticipant @ronladen17547]

I have managed to get the basics of the chassis put together, I am calling it a chassis as its hardly a boiler as per a conventional build. One problem I had was the 4 inch aluminium tube, on checking it isnt concentric, it has over 1.5mm difference in diameter when measuring around the circumference. It is not noticeable by eye, it looks perfectly round, but it is not true when measured. The ideal would have been to put it up on the lathe and turn it true but I have no means of mounting and supporting it. So I bored the 4 inch hole in the throat plate to the largest diameter, knowing this would give me roughly half circumference as a good fit and half with a gap.

I then set up the tube to the plate on the mill table making sure all was square, then I fixed the good fit with 638 retainer. Once this was dry and fixed I made up some JB weld original and using a small pallet knife pressed in the mix from both sides until I had completely filled the gap. I set it up so the good fit was at the top of the tube and the gap on the underside. There is also 4 screws which connect the tube to the throat plate but even without them the tube and plate wouldnt come apart in a hurry.

I did consider Jasons suggestion of continuing the side plate upwards and rearwards as per full size, but as I had the ali plates I decided to use them. I am going to make up a pair of steel horn plates and they will be fastened to the ali side plates.

So bear with me guys it maybe looks a bit "strange" at the moment but I think once the horn plates are fitted it should start to look a bit more familiar.

Not too good a picture but you can see the JB Weld joint at bottom of the tube.

Edited By Ron Laden on 11/11/2018 08:51:50

Edited By Ron Laden on 11/11/2018 08:52:46

[Ron LadenParticipant @ronladen17547]

There is a 1 inch Minnie boiler for sale on Ebay, its brand new and the cost is £850. I was quite surprised at the price but it looks to be very well made, said to be very accurate dimension wise, has manufacturers certificate and is pressure tested. When I thought about the work that will have gone into it I guess the price is understandable.

[Paul KempParticipant @paulkemp46892]

Ron,

Looking good. Tube not being perfectly round is quite common for general purpose tube.

That price on the Minnie is pretty reasonable for a well made model I would say. The market value of most engines rarely reflects the time expended biulding them let alone the cost of materials. General estimate of time taken to build seems to be around 2000 hours, that's a bit over a full year of 38hr weeks with no holidays, cost that at a conservative £10 per hour – £20k!!!

Paul.

[Ron LadenParticipant @ronladen17547]

Thanks Paul,

I expected the tube not to be round, was hoping for a bit better than 1.5+mm though but then it is 4 inch diameter and I guess the larger the tube the more the run out.

I did think that if the boiler maker charged his time at say £10 per hour he cant be making much, I dont know how long it takes to produce a complete and tested boiler but its obviously not a five minute job.

Going out to pick up some steel blanks for the horn plates, I,ve found some local to me.

Ron

[Ron LadenParticipant @ronladen17547]

Getting some materials together so I can progress. I have no experience with bronze, would SAE660 Bronze be ok for the axle and shaft bearings, I did see it referred too as "bearing bronze" with one supplier so assumed it would be.

[JasonBModerator @jasonb]

That's fine and nice to machine

[Author]

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