Electric Traction Engine

[JasonBModerator @jasonb]

Ron, to save some cost you could do the fronts from ERW tube, have a look at this post of mine which may help with making and soldering. Old Gas bottle may get you close to the rear size you want.

[Ron LadenParticipant @ronladen17547]

Thanks Paul/Jason thats very helpful.

I have just checked and I can buy a short length of 6 inch O/D – 10swg steel tube from my usual supplier so that will cover the front rims. Thanks for the link to your wheel making Jason, I thought that quite ingenious the way you produced them, very clever actually.

I will start having a search around for the size of gas bottles to see if any are near 9.5 inches.

Thanks again guys.

[Ron LadenParticipant @ronladen17547]

Reduced the large gear from 15mm to 10mm, 80T – 1.5 MOD getting towards 5 inch diameter, I put it up on the lathe as I didnt fancy fly cutting it in 2 passes. I dont know what it is made from, some Chinese concoction but it was awful to machine, really hard work and the hardened teeth didnt help, I wouldnt be in a hurry to do another one.

HSS wouldnt look at it and the insert tool didnt think much of it either, 10 thou cuts was the most I could go with and that was pushing it. Finish is not perfect but quite smooth to the finger so I think it will do. I now have 160 hardened teeth ends to debur and a standard needle file wont have it so probably need to get a couple of diamond type.

I have noticed that the last 20mm towards the centre hasnt cut so well but I suspect that was lack of speed. I increased the speed as the diameter of the cut reduced but I was in mid speed range which was probably not enough for the centre. I will wind the speed up later and see if a light finishing cut improves it.

Edited By Ron Laden on 07/09/2019 09:51:00

Edited By Ron Laden on 07/09/2019 09:56:31

[Ron LadenParticipant @ronladen17547]

The mid range speed (up to 930 rpm) which I used for most of the machining covered the outer half of the gear but not the inner. I dialled it up to 1600 rpm and gave it a light finishing cut and it looks to have a marked improvement.

[JasonBModerator @jasonb]

Ron, to be able to harden the steel it would need a higher carbon content than mild steel and that makes it less easy to machine where ever in the world it may come from. Looks like you got a good finish in the end.

[Ron LadenParticipant @ronladen17547]

Posted by JasonB on 07/09/2019 15:41:39:

Ron, to be able to harden the steel it would need a higher carbon content than mild steel and that makes it less easy to machine where ever in the world it may come from. Looks like you got a good finish in the end.

Thats a good point Jason, thanks.

[Ron LadenParticipant @ronladen17547]

I was using some 10mm ground bar so a good opportunity to turn the crankpin, I am thinking of assembling the pin, shaft and webs with 638 retainer and then cutting the crank out between the webs. I am assuming with this method the assy also needs pinning..?

[Michael GilliganParticipant @michaelgilligan61133]

If Loctite 638 is used properly, I can see no point in pinning the assembly.

Others may have a different view; so let me ask: What purpose would it serve ?

MichaelG.

[Ron LadenParticipant @ronladen17547]

Michael, I was just thinking that the pins would prevent any possibility of the parts working loose but I must admit I have every confidence in 638, the wheels on my locos are fitted to the axles with 638 and nothing else. I wondered what the norm is with this method of building a crankshaft and what other people do.

Ron

Edited By Ron Laden on 08/09/2019 09:31:30

[Michael GilliganParticipant @michaelgilligan61133]

In my view, Ron

If the pins were 'called-upon' to do anything; then the 638 must have already failed.

… Let's see what the others have to say.

MichaelG.

[Ron LadenParticipant @ronladen17547]

Posted by Michael Gilligan on 08/09/2019 09:40:54:

In my view, Ron

If the pins were 'called-upon' to do anything; then the 638 must have already failed.

… Let's see what the others have to say.

MichaelG.

I also wondered is the main purpose of the 638 an assembly adhesive for fitting/aligning the parts which are then pinned, I dont know..?

[JasonBModerator @jasonb]

For me it depends on the loads the crank is going to get. On the small 24mm bore engines I have been doing which will just run gently on air I'm happy to just go with Loctite usually 648 in my case.

For a larger engine then I'll add pins so that should the loctite fail the crank will hopefully still stay solid, I have read of cranks slipping too many times on model forums. hard to tell if the failure was due to the Loctite or the user but for the sake of a couple of holes, some rod and a hammer to pein the ends over I would add them.

On the hit and miss engines that have a far more violent kick when they fire I prefer to silver solder & pin after soldering for the made up ones or just cut from solid. Small IC aero engines I cut from solid.

My Minnie is silver soldered, the 2" Fowler machined from an SG Iron casting.

[Ron LadenParticipant @ronladen17547]

Thanks Jason, mine of course should be lightly loaded as the drive will be coming back through the gears from the motor so to speak but there is still a flywheel connected and as you once mentioned the crank and 2nd shaft gears could be fair whizzing around. I think I will go belt and braces and pin it, as you say its not much effort to do.

I would be interested in your thoughts on machining a flywheel from solid, it would be a new challenge for me but I have been giving some thought to how I would go about it. The flywheel is 6" x 13/16" or as near as and I can get a 6 inch round of cast iron, cost is £35 though and to be honest I havnt yet searched for a suitable casting, price or availability wise. I know you have machined them from solid and would be interested in your experience of making them.

Ron

[Ron LadenParticipant @ronladen17547]

I wouldnt have thought the material spec for the crankshaft is crucial, I am copying the Minnie crank and I dont think material type is mentioned other than steel. I am going with what I have which is EN1A ground bar 10mm for the pin and 12mm for the shaft and EN1A bar for the webs which at my scale are 56mm diameter, think it should be ok.

[JasonBModerator @jasonb]

Ron, are you going for a solid disc type flywheel as seen on road Locos and showmans engines or will you be wanting to carve out spokes?

ENIA will be fine for your crank given as it is really only decorative and only has to support the flywheel and move a dummy piston.

[Ron LadenParticipant @ronladen17547]

Jason, I was thinking of going with a six spoke wheel most of which I would machine on the lathe and then to the RT for cutting out the spokes..?

[Ron LadenParticipant @ronladen17547]

I said I learn something everyday , in the build of the Minnie wheels there is mention of solder paint I never knew there was such a thing.

[JasonBModerator @jasonb]

If doing the flywheel from solid then probably easiest to drill and tap some holes that will fall between the spokes and then bolt it onto your faceplate from behind to recess out the faces. Then over to the mill to remove six segments followed buy a roundover bit to shape the spoke sand finally some hand finishing.

Have you thought of a casting such as the Allchin or henrichi from Reeves, if it would take a 7" one then the part machined ones RDG do are good value.

Just make sure you clean off all the flux from the solder paint, it is very corrosive

Edited By JasonB on 09/09/2019 15:29:36

[Ron LadenParticipant @ronladen17547]

Thanks Jason for the tips, I am sure a 7 inch flywheel wouldnt look out of place and as you say the RDG part machined one is good value, just added one to the shopping list.

[Ron LadenParticipant @ronladen17547]

I have been sizing and positioning items scaled up to 1.625" from the 1" Minnie, I havnt followed it exactly but close.

I calculated the main axle position on the horn plate, centred the 80T gear at that position and worked back up through the gears to the 20T drive gear on the 2nd shaft. With the gears I am using it would be ideal if I moved the crank and second shaft rearward by 10mm and also move the crank down by 7mm and the second shaft down by 5mm.

The top of my boiler is square not radiused but I checked the crank throw and the larger 30T on the 2nd shaft and at the new position they would clear the top of boiler by 4mm. I realise this would change sizes/positions of other items but I couldnt see any real problems but it would be good to know if you guys can think of something I have not considered..?

Edited By Ron Laden on 10/09/2019 08:48:18

[JasonBModerator @jasonb]

As none of yours is actually working I can't see it being a problem, cylinder would sit a bit lower too though it would not hurt if its centre line was above that of the crank.

[Ron LadenParticipant @ronladen17547]

Thanks Jason, I did forget something though I just realised that I only allowed for clearance of the crank webs and forgot the con rod. It would just about clear but a 4-5mm deep slot would make certain and there is enough meat in the boiler top to allow for this.

[Ron LadenParticipant @ronladen17547]

I have not given this too much thought so am prepared to be shot down in flames but I see on the Minnie drawings that the big end bearing is a pair of shouldered semi circular half bearings… is this necessary. I wondered if a one piece bearing would work, it would need to be fitted to the crankpin when assembling the crankshaft. If the conrod and strap are then machined to a size which grips the o/d of the bearing when fitted to the crank would that not work..?

[Jeff DaymanParticipant @jeffdayman43397]

Hi Ron, it might work initially, but if it wears, how would you adjust it or replace it? The full size engines used removable split bearings for this reason.

[Ron LadenParticipant @ronladen17547]

Jeff, I did think of that but based it on the fact that the amount of running the engine would get, the bearing would probably see me out. Its not a problem though I can make it as per the drawings it was just an idea.

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