Author Topic: Potty Simpson and Shipton Short Stroke Engine (Read 78008 times)

sbwhart · « **Reply #100 on:** April 15, 2012, 03:39:58 AM »

Well got it running without having to fill it up with oil but its very gready for air my little compressor can only keeping going for about 10 seconds, I guess I may have run into the limitations of the design, they only made two of them so this speak for it self.

Stew

Stilldrillin · « **Reply #101 on:** April 15, 2012, 03:46:28 AM »

That's lovely to see Stew! Lots of parts moving around.....

"We gotta get a bigger 'presser".........

David D

Rob.Wilson · « **Reply #102 on:** April 15, 2012, 03:48:42 AM »

Nice one Stew

As ever,an excellent engine build ,,,,,,,,,, from drawings to running engine ,, first class

Rob

Jasonb · « **Reply #103 on:** April 15, 2012, 03:55:31 AM »

Another Fab engine Stew and an interesting motion to watch, you are on teh home stretch now with just the finishing touches to go.

J

BillTodd · « **Reply #104 on:** April 15, 2012, 06:11:11 AM »

Look grear Stew

Sounds like it's tight in one spot (BDC?) - it should have enough witness marks on the inside to workout where.

From my (little) understanding of the motion of these things, the piston is designed to roll around inside the 'cylinder' with ( guess) a thin film of condensate or oil 'sealing' the other side, so will always need a bit of 'clearance' . I'm also guessing it was suppose to have a sprung piston-ring type seal at either side .

sbwhart · « **Reply #105 on:** April 15, 2012, 07:05:22 AM »

Thanks for you're comments Guys

Bill:- yes one or two tight spots the bearing centres are not quite correct had to slacken thing off to stop things tightening up needs a little shimming

Your correct about the action, the origonal had spring loaded sides, it a succesfull design only two made, only one of these ran. To start with I had 0.25mm end float from the piston this was far too much lapped the cylinder width down to reduce this to 0.05mm. It is getting better the more i run it, I've also spotted areas for improvement, but happy with it, I leave it aloan for a bit and keep running it I want to make a ball valve for it and a base so i'll get on with that in the mean time.

Stew

NickG · « **Reply #106 on:** April 16, 2012, 02:53:19 PM »

Very nice again Stew, well done

sbwhart · « **Reply #107 on:** April 18, 2012, 04:44:19 AM »

Cheers Nick

Still a bit along the learning curve to go with this engine.

To days lesson:- I made the piston from PTFE it seemed a good idea at the time, I know PTFE has some strange properties and that it has a high figure of coefficient of linear expansion, but I though that shouldn't pose any problem, I measures the width of the piston and the cylinder up and made them so that I had about 0.2mm clearance fit, I reduced this down to 0.05 to try and get a better run, but as I was doing this I was having problems getting a repeat size for the piston, this morning I stripped the engine down and measured things up the clearance was size for size, great i thought, tried it for fit and it all rolled over smoothly I fiddled about a bit, tried it for fit and things had tightend up, measured up again and I had an interferance fit

Time for my morning coffee

so stuck the piston in the fridge for 1/2 hr measured up again and it had shrunk by 0.15mm.

Just done a google search on the properties of PTFE and as far as I can tell it has coefficient some 5 times greater than brass.

Time for a change of material i have some nice shash weight cast iron that John gave me I'll give that a try.

Stew

lordedmond · « **Reply #108 on:** April 18, 2012, 06:42:54 AM »

Stew

Try some PEEK that what I use on piston valves , just polo mint looking bits with a stainless bobbin

but the big but and its a big un the price it OTT, or try Polly Models they do have some PPS Polyphenylene Sulphide again sit down when asking the price

Stuart

NickG · « **Reply #109 on:** April 22, 2012, 03:06:39 AM »

Stew,

If the engine isn't going to be run on steam have you considered graphite for the piston? It worked perfectly in the two flame gulpers I made which require a very close fit and low friction. The way the graphite machines and its self lubricating properties make it an excellent choice for this. I don't know what it's coefficient of expansion is, but it must be very close to cast iron as those engines get very hot when they're running. If there was much difference it would either stop running or bind up ... it did with an aluminium piston.

Just a thought.

Cheers,

Nick

:offtopic:ps. are you going to Harrogate this year? Can't remember what day I said I'd go, will have to check the roster as will be helping on the club stand at some point!

sbwhart · « **Reply #110 on:** April 22, 2012, 04:48:43 AM »

Hi Nick

Graphite sounds a good idea, I've made a cast iron piston and tried it for fit excetra and its seem a lot better than the PTFE, I've also resculptured the bases, and I'm in the process of putting it all together, but I've got a few domestic Job to do:- muck out and change the straw in the house etc.

I don't think I will be going to Harogate this year we've had so much on over the last month that things have been building up also Daughter is due to give birth to second grand child about then and we're on standby to look after grandson.

Cheers

Stew

NickG · « **Reply #111 on:** April 23, 2012, 05:32:30 AM »

Stew,

Cast iron is probably the next best thing, that's what I used for my first flame gulper but now I want to do a graphite piston and valve for that as the next two engines ran so well with it. If you do try the graphite you'll find it very easy to get a good fit & finish, I just left mine in it's turned form to keep it nice and square and it quickly beds in to exact size. It's a bit mucky to machine but is a good lubricant anyway.

Ah that's a shame, congratulations, sounds like you'll be even busier soon then!!

Nick

sbwhart · « **Reply #112 on:** April 27, 2012, 11:19:58 AM »

Thought I'd better update the build log

1st making the cast iron cylinder.

Turning to size after drilling off set hole

The trepanning a groove for some packing,

seems to work ok without packing tough, still nice to have the option.

Shaft assembly using same method as for the PTFE

Also pinned the crank journal using soft nails.

Then whilst waiting for deliver of new 7" fly wheel made the stop valve, body fabricated in two parts silver soldered together.

Get to use the new ER32 indexing blocks to cut an hex for the valve pillars.

Worked a treat

Completed valve

And on the engine

Stew

Stilldrillin · « **Reply #113 on:** April 27, 2012, 11:38:19 AM »

That engine and valve, look as though they were made for each other, Stew!

Well done......

David D

HS93 · « **Reply #114 on:** April 27, 2012, 01:27:11 PM »

Nice job Stewart , there old panel pins, by the way where did you get the aluminum plate from for the layers of the cake ?

Peter

sbwhart · « **Reply #115 on:** April 27, 2012, 01:31:37 PM »

Cheers Guys

Pete:- I get the plate from ebay it's a bit pricey but it's the only place I've bin able to drop on the stuff.

I've got a bit more comming for another base so that I can support the fly wheel from both side.

Stew

HS93 · « **Reply #116 on:** April 27, 2012, 01:52:21 PM »

have you got a link at all, are you putting another layer on the cake ?

Peter

lordedmond · « **Reply #117 on:** April 27, 2012, 01:56:34 PM »

HS93

these do ali up to 6 inches wide 1/2 thick and no VAT

Dont know where on the big ball you are
http://www.plhillsales.com/index.asp

no connection with the firm only a satisfied customer

Stuart

sbwhart · « **Reply #118 on:** April 27, 2012, 02:27:57 PM »

This is the one I usualy get the stuff from http://stores.ebay.co.uk/The-Bits-And-Pieces-Place?_trksid=p4340.l2563

Hope this helps

Stew

Stilldrillin · « **Reply #119 on:** April 27, 2012, 03:13:19 PM »

This looks very promising....... http://www.aluminiumwarehouse.co.uk/cutting_calc.php?gclid=CJ-9oMvx4K0CFQcSfAodcV839Q

I'm needing a piece 10" square x 10mm. Will order, soon.

David D

sbwhart · « **Reply #120 on:** May 09, 2012, 02:10:38 PM »

Got the new base for the larger fly wheel made and the bearing housing plus one or two other bits, cleaned it all up and got it prepaired for painting but bin held up on this front due to the rain we've had the last couple of days. Taking the base round to men in sheds to have it planed and edged.

With a fair wind i should have it compleat next week.

Stew

sbwhart · « **Reply #121 on:** May 20, 2012, 07:42:38 AM »

Well got it all together

I'll show some smatter pics and a vid later, at the moment i've got my Boss breathing down my neck, I've bin a bit obsessed with this engine, and the jobs are building up.

I think it looks great but my boss said its a bit too Tarty for me

Stew

Divided he ad · « **Reply #122 on:** May 20, 2012, 07:56:50 AM »

Nice one Stew

Looks great

How's it run with the bearing support? I suppose I'll have to wait for the vid' like everyone else!?

Quote

I'll show some smatter pics and a vid later, at the moment i've got my Boss breathing down my neck, I've bin a bit obsessed with this engine, and the jobs are building up.

I think it looks great but my boss said its a bit too Tarty for me

They'll never understand Stew..... Never!

Ralph.

HS93 · « **Reply #123 on:** May 20, 2012, 08:42:05 AM »

very ver nice ,

but where is the man and woman gone of the top

Peter

sbwhart · « **Reply #124 on:** May 20, 2012, 12:09:07 PM »

Thanks Guys

Ralph:- posted the vid elsware but here it is any way

Pete I'll bring it with me when we nip over to you're place.

Stew

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Author Topic: Potty Simpson and Shipton Short Stroke Engine (Read 78008 times)

Rob.Wilson

lordedmond

lordedmond