Brian’s 1″ Minnie Traction Engine

[Brian AbbottParticipant @brianabbott67793]

Hello Richard,

Thanks for the reply, will see how i get on..

[Brian AbbottParticipant @brianabbott67793]

Hello all.

Quick question regarding the eccentrics, should i drill them to allow access to the grub screw to adjust the timing ?

Also, once i finish the motion work i plan to start the front end, not sure if to go down the roller root as something different, has anyone done this ?

Thanks

[Brian AbbottParticipant @brianabbott67793]

Hello.

See above.

Anyone any thoughts on drilling this eccentric ?

[JasonBModerator @jasonb]

If you were to make the oil hole so that it is aimed towards the middle of the crankshaft the that could be drilled just large enough to clear your hex key. This will be the least likely to weaken the narrow eccentric strap as you will be drilling through the thickest part

[Brian AbbottParticipant @brianabbott67793]

Hello all.

About to start making the eccentric rods for my engine, unsure if to machine from solid or do as the book says and fabricate, can i ask what others have done ?

Thanks

[JasonBModerator @jasonb]

I did my Minnie as the book but when I came to do the 2" Fowler I cut from solid probably helped by the fact I had a mill for the Fowler

[Brian AbbottParticipant @brianabbott67793]

Thanks Jason,

Have soldered them, stick to what the book says,

[Brian AbbottParticipant @brianabbott67793]

Quick update on the Minnie progress.

Motion work complete at long last.

[Brian AbbottParticipant @brianabbott67793]

Moving on..

Want to make a start on the chimney saddle, ordered a casting but not really sure where to start.

I’m ok with the machining, I am unsure what to do with the finished cast surface.

The casting has the usual flash and burnt on bits, anyone got any work on progress pictures of this part ?

Thanks.

[Brian AbbottParticipant @brianabbott67793]

Hello guys, after some more advice.

Whats the best way to form the curved piece of the perch bracket to match the smoke box ?

[JasonBModerator @jasonb]

Clamp by the chimney flange to an angle plate or if you still have the chucking spigot then that can be held in a collet block so the part is on it's side. Then use a boring head to cut the concave surface.

[Brian AbbottParticipant @brianabbott67793]

Morning Jason, thanks for replying,

Its this bit I'm not sure about, should i try and find / borrow a set of rolling bars or should i just form it round a bar ?

[Paul KempParticipant @paulkemp46892]

I have not built a Minnie but looking at the thickness it should be quite easy to pull that round by hand. Technique I have used for similar parts in the past is to set two round pins vertical in the vice, say a couple of bits of half inch round bar for that job, just over 1/16" apart, put the plate between them and gently curve round by pulling it and checking against the smokebox as you go. I have made tyres this way from 1/8" and thicker quite satisfactorily. You might want to clamp it on to a filed plate edge on in the middle though if you silver solder the bracket on though as it's likely to change shape when you heat it!

Paul.

[JasonBModerator @jasonb]

Sorry Brian, read it too fast this morning.

From memory when I did mine I bent it on the end of a longer strip around some bar that was a bit smaller diameter than the smokebox maybe 2.5" dia to allow for spring back.

I have sinced used the 3 pin method that Paul describes to bend metal and that works well too, just work along in small increments to get a steady curve

[Raymond GriffinParticipant @raymondgriffin40985]

Hi Brian,

I attach a couple of photos to show how I did mine recently. The diameter of the cut was established using the method shown. The support was bent around a metal bar. You will need to turn your computer screen around to get the photos upright. Sorry, but no matter how I upload my photos to this site they come out, the wrong way up. Pleased to hear that you have completed the motion work. I am struggling with mine.

Ray

Edited By Neil Wyatt on 02/04/2019 17:14:13

Edited By Neil Wyatt on 02/04/2019 17:15:55

Edited By Neil Wyatt on 02/04/2019 17:16:36

[Brian AbbottParticipant @brianabbott67793]

Thanks for the feed back,

Raymond, nice to see it progressing, not heard from you in a while.
Jason, you say 3 pin method but Paul only mentions 2 ?

Is this right ?

Edited By Brian Abbott on 02/04/2019 16:52:29

[JasonBModerator @jasonb]

No three pins like this, in effect you are mimicking a pyramid roller but just squeeze the work and then move along say 1/8" and squeeze again. The photos above used the Vee block edges as the rear two pins and the bit of brass as the third but the edge of the vee block does leave a mark.

This is the sort of thing.

[Brian AbbottParticipant @brianabbott67793]

Hello all.

Bit stuck and i need a little help.
Just starting making the parts for the front wheels, looking at the drawing the hub looks to be offset to the center of the wheel but i cannot see a size on the drawing, anyone any idea ?

[Richard S2Participant @richards2]

No Offset Brian. Central part of the hub is central to the rim width, so you can make the Wheel build jig where the wheel just needs to be turned over to set the opposite spokes (unlike the rear wheels).

What I think you may've noticed is the licence of the drawing not showing equal widths of the outer covers before the inner one starts to taper down?.

The inner cover provides 3/16" additional spacing each side on the front track width.

Can't offer pics, as I modified those inner covers on mine.

Regards.

[Nigel Graham 2Participant @nigelgraham2]

Re Jason's suggestion way up near the top, on drilling the eccentric strap.

This may be affected by the particular design but I have just considered a similar problem on my Hindley wagon engine, which I am building with no drawings available.

I'm keying the eccentrics and locking with grub-screws, but the screws are the salient part.

I drilled the oil-way tapping-size for the intended screw, right down through strap and sheave to the bore; enlarged to clearance part-way into the sheave then enlarged the hole in the strap part-way to give the oil reservoir (of for tapping for an oil-cup, on other engines).

HOWEVER….

If you intend making the eccentrics adjustable, making an access hole in the strap is pointless because once you've slackened the grub-screw and slipped the sheave round, the screw is inaccessible for tightening!

Normally, on all miniature engines' designs I've seen, the eccentrics may be grub-screwed but angular adjustment still necessitates removing the strap at some stage in the process.

(In full size practice, with some exceptions, the eccentrics' angles of advance were normally determined on the drawing-board, and they and the crankshaft were keyed at those angles. The main exceptions were on stationary engines for driving factory plant in one direction all the time; but allowing the engine to be reversed if required by the individual installation. To do so, a separate disc was keyed to the shaft, and the eccentric itself, bored to slip-fit the shaft, was carried on the face of the disc by clamping-screws working through arcuate slots in the sheave. It was essentially a slip-eccentric gear as on some small miniature locos., but intended only for on-installation or very infrequent reversals; or to alter the cut-off if new machinery altered the engine's load.)

[JasonBModerator @jasonb]

No offence Richard but if you look at the middle of the hub where it's diameter is reduced it has not been drawn central to the tee ring. Think it's about 1/32" offset. Either way won't really affect things

[Brian AbbottParticipant @brianabbott67793]

Thanks for the replies chaps, does look offset but as there is no dimension i would imagine it’s just how it was drawn, anyway i’m going with equal about just to keep the wheel jig the same for both sides, thanks again

Nigel, see your point regarding having a clearance hole, i am not brave enough to key the eccentric, i have found an article in the model engineer that explains how to set the timing using a DTI so am going to try that method if i live long enough….

[Brian AbbottParticipant @brianabbott67793]

Hello all.

More help needed,

When i made the rear wheels i soldered the hub and spokes using cup alloy soft solder paste, after doing this and for some time afterwards i suffered from rust around the joint.

I am about to solder the front hubs, is there a better way of doing this ?

Is soft solder paste the best option, would silver solder ( paste or rod ) need to much heat ?

Could glue with an epoxy but don't really want to do this.

Thanks for any help.

[Raymond GriffinParticipant @raymondgriffin40985]

Hi Brian, I was worried about flux residues causing corrosion when making wheels for my Minnie. I decided to use JB Weld resin. The long setting time allowed me to ensure that everything was correctly placed. It worked well, and I can see no advantage in using solder. I add a photo of my rear wheels during construction. The wheel is mounted on a flat, circular plate that could be rotated around a central spigot.

Have you managed to set the valve sequences on your Minnie? I am finding it very difficult and tiresome as the eccentrics are not easy to manipulate.

Cheers Ray

[Brian AbbottParticipant @brianabbott67793]

Hello Ray.

Not thought of JB weld, will have a think about that.

How strong does it set ?

Not ready to set the eccentric yet, need to drill the exhaust port into the cyclinder but have held off until i fit the chimney base, am sure when the time comes i will fail.

Front wheels progressing ok, fingers crossed i will have it on its wheel soon.

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