Member postings for Steve Withnell

Hi Nick, yep it isn't ideal, but it's a consequence of needing somewhere to put the governor drive pulley. To be honest, that how it is on the plan and I haven't bothered to think through a better option. It worked out OK on the Victoria though.

https://www.youtube.com/watch?v=R6rgZ-7Y3t8

I am interested in knowing if anyone has come up with a better design for mounting the governor on the Coombes - it doesn't look particularly good as planned (didn't on the Victoria either, but there is space for alternatives).

Steve

Made some new studs, a right fiddly job - 7/16" long, 7BA. Only six though, could have been worse. Anyway, the sheave has been finished. Because the finished engine will be fitted with the Stuart governor the sheave has no boss, this makes room on the crankshaft for the governor drive pulley.

The sheave is turned to its outside diameter from a short length of steel bar:

Then I set the eccentric throw:

And then bored the hole for the crankshaft so it's nice fit, then turned the little cheek that acts as a spacer:

Next step is to part off - on the eccentric. This is advice from Harold Hall's build of the Stuart V10, the logic being that the parting tool will break into the crankshaft hole evenly around the circumference. He also strongly recommends the use of a rear parting off tool, which I don't have.

Parting off didn't really cause any evil demons to appear, slow and steady, show no fear...

In order to finish off the machining, I used loctite to fix the half finished sheave onto a short length of bar, here I've already turned the first side if the sheave:

Using the eccentric strap as a gauge to ensure the diameter is correct:

Now the workmanship is exposed:

The sheave is a perfect fit with the strap, nitwit put a very nice slot in the wrong place in the strap...However, it does not matter and only we know . Because the sheave has no boss now to take a grub screw, the grub screw is to be fitted in the centre (ahem) of the sheave. If you think the sheave is looking a bit of a funny colour, it's because the loctite needed getting pretty warm before it would give up.

So that's the sheave done. Next installment will be fitting the cylinder to the table.

Steve

Thanks Norman. The Stuart "studs" are not strictly studs, just short lengths of threaded rod...So been making 7/16 studs.

Steve

Thanks Clive, I have tapped the holes about 4.5mm deep, so I just need to make some longer studs then. Stuart want £15.50 for 25. Ouch.

Steve

I'm moving ahead with the JC quite nicely - but have a concern I'd like views on.

Stuart provide 3/8" studs to fasten the cylinder to the table. The table is 3/16" thick and the nuts are 3/32" thick. This leaves only 3/32" of stud thread in the cast iron cylinder. The studs are 7BA. Whilst I'm not going to tighten the nuts down with a 6ft length of scaffolding pole - is 3/32" of thread engagement enough? I used a 2mm tapping drill which is slightly tighter than recommended by Stuart.

Steve

https://www.dropbox.com/s/o4466cl48ct2dws/P1000196.JPG?dl=0

This should take you to a photo of the eccentric strap I made for the Victoria - you can see how much more material is in this strap, than the one I just finished for the JC. They are both machined from the same extrusion, so the designer must have assumed a lot of metal would be lost in the hacksawing process...

Here a link to my library of photo's for the Victoria I built:

https://www.dropbox.com/sh/dvrpnbirsgppr3h/AAAGfAnbQK1d6i7PT17AWUr1a?dl=0

And here is a link to my James Coombes photo library:

https://www.dropbox.com/sh/zue22yuxsike8wf/AADVxsMj4TptMLSRTp6wZmQVa?dl=0

You should not need either a password or need to subscribe to get access to the libraries -

Steve

I got fed up tripping over that unfinished James Coombes, so took another swing at it -

I've left the crankshaft over length whilst I get the eccentric and governor drive pulley fitted.

Making the strap - same method as I used for the Victoria. When I made the straps for the Victoria, I split the extrusion with a thin slitting saw- this approach makes a nice tidy job, but leaves far more material in the strap than is required. It means that the outer of the strap looks quite 'egg shaped' and not concentric with the sheave.

For the Coombes I used a hacksaw to split the strap extrusion and the cleaned up the two halves in the lathe, so now the strap will 'look right'. Well almost. The issue is purely one of aesthetics, no issue mechanically.

I make the initial hole with a slot drill.

Here is the tool I use for producing the groove to take the sheave rib - This was made from an old number stamp. I'm not sure how you can do jobs like this without grinding a bit of steel to the right shape.

Now I've started, trick is to keep up the momentum!

Steve

Edited By Steve Withnell on 27/06/2015 20:46:16

Edited By Steve Withnell on 27/06/2015 20:49:37

You could try:

Please contact P L Hill with any queries or requirements:

01274 407343
07585 772183

67, Grasmere Road,
Bradford,
West Yorks
BD2 4HX

They advertise 4" diameter, but might know how to get hold of 8"

Steve

What's great about being a novice is that you can crack on happily making round things square, square things round and not realise you did wrong until you start reading the ME forum posts!

Steve

That takes me back 35 years to a DEC GT40 which had a vector display. Think it had a PDP-11 processor, but might have been an LSI-11. Lunar Lander only had one mountain IIRC, but if you flew fast enough you could go right through the mountain and land safely on the other side.

Oh the waves of nostalgia... that was the time that the National Coal Board released a version of Space Invaders ported to Basic.

Steve

I've used a number of these soft end mandrels from ARC over a period of time the first use:

All I did with this one was drill and tap a 12mm hole 50mm deep to create a backstop for my lathe chucks. I didn't have any issue at all with using 'normal' drills or taps.

Another application was to make a mandrel for holding slitting saws (or "Shitting Saw" as an ex- boss's PA once titled a business investment proposal), but I probably didn't drill close to the shank for that application.

I have noticed that some are not as "nice" to machine as others, so maybe they are not consistently 'soft' from batch to batch.

Steve

I've always given the tape a good stretch to wrap a joint and never used any PVC tape over wrap. The only problem I've had with it is getting it off afterwards!

Steve

Don't think so - my Dad used cloth self amalgating tapes to fix burst top/bottom hoses on car radiators.

The self-amalgamating tape I use is a purely a synthetic plastic type of stuff for sealing electrical joints to keep the weather out. Not sure how it would cope with very high temperatures.

Steve

I've managed to grip quite short lengths using this trick.

Steve

I have a good quality 6 inch RT (It happens to have 4 slots). I barely eat enough spinach to manage the 6 inch never mind an 8 inch. This is quite an issue if you are setting the thing up with the rotary axis horizontal to the bed of the mill. By the time there is a 6 inch+ chuck bolted to it, there is a lot of weight to deal with.

So I'd buy the biggest you can lift without needing a truss.

I did try clocking up a part in the 4 Jaw, found it such a tedious performance I now use a collet chuck when I can, because you win back a lot of lost height on the machine (or length on the bed.)

Making or buying a backing plate is hardly a big deal to get the versatility you need.

Steve

In 1975 they were quite exciting, I can't believe they remain the "go to" device for this sort of thing 30 years on!

Steve

Hmm the nuts that I have which are specified as 1/4- 32UNS -2A, don't fit the enya glow plugs I have. The pitch is off just enough so the nuts don't run on to the plug thread. Don't worry, I'm not intending to fit nuts to my plugs, it was just an easy way to test Tony's point above.

Steve

Thanks for that - I must have one in the box then!

Steve

Is this normally referred to as 1/4 - 32 UNEF?

2A appears to be the thread tolerance.

Steve

http://www.ebay.co.uk/itm/RAYCHEM-S1030-HEATSHRINK-TAPE-HOT-MELT-/141503880338?pt=LH_DefaultDomain_3&hash=item20f249dc92

This one is adhesive and 20mm wide.

£26.58 for 10metres.

Steve