triple expansion engine

[swilliams]

Very impressive Peter :bow::bow: Hell of a lot of webs in that

regards
Steve

 

[Deanofid]

That's an impressive fabrication, Peter. I like watching a fellow use the machines he has on hand.
(I have a Taig lathe, too.)

 

[peatoluser]

well, between the snow, cold weather, getting dragged round the shops and general festivities, i managed some shed time.
as the material for the base blocks hadn't arrived I decided to make the main bearings.
because i'm milling the slots on the lathe, and the cross slide only has 1 3/4" travel, I made them from 1 1/2" lengths of 1 1/4" dia. bronze bar, first squaring the bar to 13/16 by 9/16 cross section in the 4 jaw chuck.

I have a collection of various thicknesses of 4" by 2" flat bar, brass and plastic shim , so I can set work on the cross slide with some degree of accuracy as regards it's hight. To align the material with the cross slide axis, I generaly screw on the faceplate and hold the work flat against it while I clamp it down , or align it using a square. I check it with a DTI and its very rare that it needs adjustment.

when i came to slice the bar, I found that the slitting saw arbor I had made didn't give me enough depth of cut, so had to remake it but this one is just held in the 4 jaw.

the next job was to put them in the boring fixture I had made and bore them all out to 3/8"

 

[peatoluser]

Heres a photo of them in thier slots

i need to make the bearing retainers and bolt the bases down to fully check the alignment. As 3/8 bar is nominaly one and a half thou down on size, a piece should go through without binding. If it's tight i'll need to fettle the slots. trying to lap in the bearings would leave me with oval and over size journals. which brings me to a question. I intend to use a built up crank. If i use 3/8 BMS (CRS) will this give me too much clearance? or should i use 3/8 precision ground BMS and lap the bar down were the bearings are to give, say, half thou clearance?
thanks for reading the post
yours
peter

 

[Seanol]

Peter,
All I can say is WOW!

I learned how to add webs and what a difference it makes to the look of the model!

Thanks,
Sean

 

[Ken I]

Use silver steel for the shafts - it is precision ground and generally better quality - its obviously a bit more expensive.

Ken

 

[peatoluser]

managed to do a bit more to the engine this past week.
first up, I decided to make the chock blocks that the base stands on. As there's 84 of them I wasn't particulary looking forward to the job, but at least they are now out of the way.

first I made a simple L shaped jig to cut them to size (3/16 sq. bar by a 1/4 long)

didn't make a jig to drill them, but with hindsight probably should have. i used scrap pieces of 3/32 and 1/8 plate to mark the centres , drilled and tapped to 6BA. here they are in place

I then gave the bases a coat of white primer to protect them and also removed the webs on the vertical parts of the bases. Don't know why I fitted them in the first place as they dont appear in the illustration i'm basing them on. They just made it an utter pain to bolt them together.

I decided to make the crankshaft next. This is a built up affair as I think that turning it from solid would stretch me and the Tiag too far :-\

I had already made a fixture for turning eccentric sheaves, so adapted this to bore out the crank webs

The drawings i'm using show plain square crank webs, but I came across a video clip on youtube that showed a (smallish) fullsize triple with nicely curved webs, so out came the files and I gave them some bling

I took Kens advice and used silver steel for the shaft. to set the 'web angle' I placed the shaft on 2 blocks, and the big ends on two smaller blocks. If my maths is right the difference in hight is just half the crank throw. Used loctite but undecided whether to pin as well.

On the original drawings , because the shaft is solid, the inside eccentric sheaves have to be split. But as i'm using a built up design i figure i may as well make all the sheaves solid and slide them on the shaft before fixing on the final crank. So next job is to make the sheaves.

 

[NickG]

Wow, that's an incredible amount of work Great stuff and making brilliant use of the peatol lathe there. :bow:

Nick

 

[peatoluser]

foe various reasons didn't get much shed time in february, but hopefuly i can now get back into the engine.
next up to make are the eccentrics. for these i was able to use the 'V' faceplate i detailed on another thread.
here it is drilling the holes at .140" offset.

these are held onto the shaft with grub screws and to drill these centraly i first drilled and reamed a hole in some angle

then it was a simple job to calculate the height of a spacer bar to place the eccentric on the lathe axis when located with a pin to the angle

I decided to try and give the eccentrics a bit of 'polish' by drilling and filing a couple of lightening holes in them , like their full size counter parts.

the trouble is, although i don't mind filing, i kinda hate using needle files, so i cobbled together a needle filing machine to fit the peatol

it works quite well. so much in fact , i've ordered some proper type B (1/8 shank) machine files. although i'll probably have to modify the design somewhat. when they arrive i should be able to make short work of the rest of them
peter

 

[peatoluser]

After messing up the first set, I had to remake the eccentrics, but finaly managed to finish them.
The next job was the straps. as I wasn't using castings I used slices of phosybronze bar.
these were faced off and rough bored 7/8

I located them on a peg on the cross slide so I could mill a flat on them

This aloud me to atleast split them all the same, if not directly on centre. they locate against a strip of metal bolted to the slide

they were then soft soldered together and
I then centred them on the faceplate and finished bored them 29/32 with a central locating groove of 31/32 for the eccentric.

It was then a case of filing them to profile. I also decided to drill the eccentrics for two dummy bolts (9BA) to make them look like there full size counterparts

 

[compspecial]

This project is so inspirational Peter! wonderful workmanship, and all done with a minimum of sophisticated equipment, good luck with your progress.
Stew.

 

[peatoluser]

Thanks for the compliment stew, but my workmanship is probably only marginaly better than my photography!
yours
peter

 

[nfk]

:bow: :bow: :bow: :bow:
Wont say any thing else!

 

[bearcar1]

I applaud you for demonstrating so excellent and well thought out fabrication work. And all with the tooloing you have available at hand. BRAVO!!! :bow:

BC1
Jim

 

[peatoluser]

Thought i'd make the bigends and connecting rods next.
the big ends were straight forward split bearings , but I thought i'd give them some bling
(my apologies for the crap photos. the compact seems to have a mark on the lens- i had intended to treat myself to a new camera but blew the budget on tooling at the harrogate show)
I milled out 2 recesses on the sides of the bearing, turned up some barrel shapes , filled these in half using my filing rest and then soldered them into the recesses so they look more like full size practice. after spliting i bored them out using the same jig i used on the eccentric straps.

the connecting rods i made from 1 dia bar
first turned the profile

the next step was to square the stock. I thought about using my filing rest, but there was an awful lot of metal to remove, so decided to remove to the bench vice, hacksaw most of the waste away and use my bench filing jig to bring to size.

by the way, the jig i initialy made to help in filing thin sections. here it is as initialy concieved with some loco spring buckles. By filing down to wear strips, it saves a lot of time in continualy measuring and checking progress. when the strips (just pieces of scrap plate) get too 'filed down' just fit 2 new ones.

the rest of the work was just drilling and basic filing. here are the three stages of production in glorious three-quarter blur-o-vision so nobody can spot all the mistakes or out of squareness :big:

thanks for looking
peter

 

[peatoluser]

before making the eccentric rods I thought i'd make the bushes for them as well as the bushes for the reversing links as these are almost identical.
heres a brief sketch of whats required

used the 4 jar to turn some pieces of round phosy bronze to 3/8 by 5/16 square, then sliced off 12 off 5/32 pieces and 12 off 3/16 using slitting saw and cross slide table.
thought about making a drilling jig to drill the holes, but discounted this method as they are quite small and fiddly, and came up with this method instead that somepeople may find interesting:-
filed up a piece of 3/8 bar so it was about 1/16 below lathe centre hight then clamped this, edge on, to the milling table (actualy a block of 2 * 4 * 1/2 steel). i then skimmed the top with a 5/32 cutter, set up the cross slide stops i'd made, then it was a case of clamping each of the first 12 blocks on top of the bar and drilling the 1/16 holes. because the bar was the same width as the blocks they were easy to align.
heres the photo of the first stage, centre drilling the 1/16 holes

I then skimmed the top with a 3/16 cutter, drilled the next 12 blocks, and finaly used a 5/16 cutter to skim the bar and drilled 3.9mm (i'll finish holes with hand reamer) in all 24 blocks. I think it was a lot quicker than trying to use the drill.
here they are all done

the 3/16 ones have bosses machined on the front. I just used loctite to fix 4 of them onto pieces of 5/32 bar, turned one face, removed from collet, and as long as i then removed it and loctited a new block on, by the time i'd done the other 3 (repeating the process) it would have cured enough to machine the next.
i guess the next job is the eccentric rods.
thanks for looking
peter

 

[steamer]

Blurry or not, still looks great! Nice set ups!

Dave

 

[ShedBoy]

Mint looking engine. You really get every ounce out of that little taig. Every post has that Taig doing something different. :bow: :bow:
The filing attachment is great. I will follow with much interest.
Brock

 

[peatoluser]

with the little bearing blocks made, time to start on the eccentric rods.
the drawings show these in 2 parts, the 'fork' being separate and screwed onto the rod, but I decided to make them as one piece so as to look more like their full size counter parts. although the sketch I used (from Newnes Marine Engineering) as a basis was probably more for crossed rods whereas the engine I'm building is open roded.
used a similar method of manufacture as for the connecting rods, but to make sure that I could file the fork on, I had to turn turn the shaft so it was off centre otherwise I would've had to make them from 1 1/2" bar and as the stem is 5/32" dia. tapering to 1/8", that would've been an awful lot of metal to remove for the peatol!
the photo shows the stages of manufacture. 3 down and 3 to go. hopefully should get them finished this weekend. the 2 pieces of grooved bar at the front are just a simple filing jig to help me round off the edges of the blocks while keeping the top and bottom faces square.
the rods are 2 3/8" high and all the nuts are 10 BA

thanks for looking
peter

 

[peatoluser]

After filing the eccentric rods decided to have a go at the expansion links and die blocks. Although the links looked like a straight forward filing job, the drawings showed the die blocks having a straight slot. For some reason I can't fathom now, I wanted these to have a curved slot and I'd had enough filing for the time being, so decided to try and design a curve milling fixture for the peatol. well, I say design, but I just grab what's available and make it up as I go along.
this is what I ended up with: disassembled

and assembled

as you can see, it's just a plate that can pivot on a fixed back plate. I used my beam trammels to mark out a series of arcs (1/4" spacing), then centre poped these on a centre line with the swivel hole (reamed 10mm). In use I line up the nearest hole with a pointer held in one of the collets, and if the radius (as in this case, it was 3 3/16") isn't a multiple of !/4", I adjust the cross-slide with the help of a DI, as here

here it is being used to mill a bronze disc that will become part of the die blocks

and here, some gauge plate for the expansion links (i used my cross slide stops to control the thickness

did it work? well, yes and no. I did eventualy get all the parts made, but not without going through some cutters, fortunately I'd only paid a pound each for them, but it still irked nonetheless.
I had hoped to get away without making a lead screw for it, relying on friction (the pivot is tightened with a nyloc nut) and a long allen bolt as a handle to control the cutting rate, similar to the small rotary tables i've seen here to round of the end of rods etc. (appologies for not remembering who posted the original idea). I think with the cutter being so far from the centre I had a great deal of trouble trying to control it when it was breaking through. cutting the slot was fine. I had the same problem when I was milling on an edge. but i did eventually end up with this

that became these

was it worth it? I could have filed them quicker than the time it took to build the jig, and by the time i'd filed up the die blocks...well... i could only see the curve in them because i knew it was there... but the expansion links would only fit in them one way round and they were all the same thickness. So i think i will carry on developing it. I just need to make a lead screw for it. also i think the scapper plate (stops me ploughing into the swivel plate with the cutters) would be better if it was bolted from the back. and i think I could do with drill/reaming a hole in the pivot bolt. this should enable it to be able to mill arcs centred on a hole. anybody got any suggestions about the best way to go about these or other improvements will be gratefully recieved ..oh.. and my appologies for this last photo.... the kid in me couldn't resist it :big: :big:

thanks for looking
peter