My First Stationary Engine

Will have a look later for you

If my calculations are correct and working from the drawing dimensions I make it that the piston at BDC covers the inlet/outlet valve, would that be correct..? I imagined that at BDC it would be just shy (above) the valves but maybe not.

Hi Ron,

On the original muncaster engine the top of the piston is half way across the port at BDC, which is how I set mine.

Not sure it would be a good idea to cover the port completely, but I'll be interested to see what Jason thinks.

Geoff

As far as I can make out Julius has it so that there is some of the hole exposed at BDC

Crankshaft ctr line to cylinder pivot = 78mm add to that the distance from pivot to ctr of hole in cylinder = 15mm Plus half hole diameter (3.5 / 2) = 1.75 giving a total length of 94.75mm.

Big end 13mm less hole set down 5mm = 8mm plus spigot = 6mm plus unthreaded length of piston rod ( 59-7) = 52 Plus piston thickness = 8mm Total length 74mm

94.75 - 94 = 0.75mm of hole exposed

This is fine as the area will still be larger than the anount of port open will be less than that until the piston is 5mm or so on it's way back up by which time all the 3.5mm hole will be exposed. I would not want to see it totally covered as you may get a bit of bounce if any trapped air is being compressed by the piston if there is no way out for it.

Thanks Jason, thats good news I will carry on as per the drawn dimensions, also pleased with the 0.75mm of the hole exposed thats what my reckoning came out at.

One other thing that I have considered, unless I am missing something is there any reason why the inlet/exhaust holes cant be run straight through to the back of the column instead of through 90 degrees and out of the sides. I was thinking it would be a tidier option for the airline connector than out of the sides...just a thought.

Thanks

Ron

You could take them through to the opposite side but if using M6 threaded unions they would be too close unless you offset the threaded holes so they were further apart.

Alternative would be to drill right through 3mm then open the ports to 3.5mm for half depth. You could then simply Loctite in a couple of bits of 3mm tube and just push a hose onto whichever one you wanted.

J

PS I think I have sorted out the geometry for a reversing version at almost original Muncaster size

Thanks Jason, I was thinking of just one M6 push in type connector and leaving the exhaust hole with no fitting..?

The reversing version will be interesting to see.

Ron

Morning Jason,

I am in the process of turning the piston in some 6082, I am going to give a pair of oil V grooves a try which you mentioned, I was thinking 2mm in from each end..? also how deep do the grooves need to be, I,m guessing not too deep..?

Thanks

Ron

0.5mm deep would do and your 2mm in will be fine

Thanks Jason.

Jason,

I found the drawing for this little engine on the "MEWS Models to Build" site and this morning I found your build thread of the Monitor Ball Hopper Hit n Miss Engine, I have to say that it is seriously impressive, quite a large lump of an engine and quite involved to. The setting up for machining of some of those awkward castings was impressive in itself let alone all the other parts you had to produce.

Excellent stuff Jason was it a good runner.

Only had time for two small parts today, the big end and the piston. The piston is 0.004" oversize, hopefully that is enough for adjusting its size ready for lapping in once the cylinder is honed.

Should have some brass bar on Monday so I can make a start on the column.

Looking good

Thanks for the comments on the Monitor, there are several more of my builds on there though some may only be on the DVDs now but all somewhere on the web as David just takes text and images from a build thread.

Turned up the crankshaft and its bearing this morning, went with a different approach to the drawing. The drawing shows the crankshaft as a plain shaft with the crank arm added (close fit) then pinned, also the same fixing for the flywheel.

I have turned up the shaft with a stepped boss as a one piece to which I will lightly press on the 4mm thick connecting arm plus a dab of retainer. The end result will look the same, I thought it just bit easier then machining up the one piece arm and boss.

Edited By Ron Laden on 02/02/2020 09:29:08

Ron, I have found a nebuliser has enough air pressure to run these small engines, then you can see for tight spots and then adjust the parts for free running. Also the nebuliser will be handy when old age sets in, the best quality ones that my father has seems to have more pressure than my £40 one, but works a treat.

Bob

Edited By BOB BLACKSHAW on 02/02/2020 10:33:09

Hi Bob, I would never have thought of a nebuliser but I needed a new airbrush compressor anyway so I have killed two birds with one stone (hopefully)

The engine looks nice which model is it..?

Ron

Just out of interest it is quite recent that I got myself some GT inserts, previously I had been using MT inserts and HSS tooling on most of the lathe work. I have to say that I am very impressed with the GT type, not only are they excellent on alu, brass and the like I have found them very good on steel, well on EN1A at least.

The crankshaft I turned this morning from 1/2" EN1A down to 5.0mm and used a GT for all of it, not just the finishing cuts. I guess there must be a limit on the depth of cut but I took some 1.0mm cuts with no problem at all and even at 1.0mm the surface finish was very good.

I dont know how you guys find them but I think they are excellent.

Edited By Ron Laden on 02/02/2020 17:16:24

Ron, Stewart Hart has drawings of a number of small engines, I sent him a message and received them via e-mail.

Bob.

Jason, I have found some Pine dowel in the shed would that do for the cylinder honing or does it really need to be hardwood.

Ron

Should be OK

**GT inserts are good for wood too

Edited By JasonB on 03/02/2020 13:15:43

Thanks Jason

I will give it a try.