Jowitt MkII Popett Valve Steam Engine

[b.lindsey]

I have been following along too Jason. Nice work on that cylinder!!

Bill

[Jasonb]

Thanks to Marcus for pointing out I had put the main bearings onto two drawings, sheet No 6 has now been revised and the link at the end of my last post will take you to it.

Good to know someone is reading the thread 

[Don1966]

Thanks to Marcus for pointing out I had put the main bearings onto two drawings, sheet No 6 has now been revised and the link at the end of my last post will take you to it.

Good to know someone is reading the thread 

Jason I been reading the thread but not the drawings. So I quests I need to start looking at the drawings also.......

Don

[Jim Nic]

Like Don said.  I'm reading as hard as I can    but confess I haven't looked at the drawings as yet, I figure if you're doing them Jason they'll be fine. 
Jim

[Jasonb]

Crankshaft

I had intended to make this from 10mm PGMS (Precision Ground Mild Steel) which is what I have spec'd on the drawing but could not pick up any at the time I wanted it and postage on one bit of metal would have been high so I opted for some 10mm Stainless steel which I already had, either would do the job.

The main shaft can be turned down to 112mm long which is right for the two Perseus flywheels that I used. If you buy different flywheel castings or want to add a pully then you may need a longer length.

The pin can be faced off to give the required 22mm overall length then reduced at both ends to 8mm dia for a length of 6mm



Machine up two pieces of mild steel 12x6x24mm and then holding them in the vice drill and then ream the 10mm and 8mm holes. If you use a vice stop it saves having to locate the edge of the second web.



Clean up all the parts with solvent so the loctite will make a good bond and then start assembly. I did it in two stages, firstly stick the pin into the webs using the shaft to keep things lined up. Then when that has set the pin/webs can be bonded to the main shaft, I supported them in a couple of Vee blocks while things dried.



I'm more used to silver soldering crankshafts or cutting from solid so decided to pin the joints for good measure. Drill 1.5mm cross holes and lightly countersink.



Then push some 1.5mm steel rod through the holes and pein over the ends with a hammer.



All that remains is to cut out the middle of the shaft that is not needed and file the ends flush with the insides of the webs, the ends of the pins can also be filed down at the same time.

Check that the crankshaft turns smoothly in the bearings and make any adjustments that may be needed as its easier to do it at this stage. Once happy that everything turns freely the base can be joined together. I used a small amount of JBWeld spread over the 4 joints and then screwed the parts together on a flat surface making sure that the crankshaft turned as the screws were nipped up.



If you leave the feet off it is easy to clean up across the whole end to remove excess filler and any high spots if the parts don't quite all lay flush. Once that is done the feet can be stuck in the same way. I prefer to use an easier to sand filler for cosmetic filling so some U-Pol car body filler was used to fill the screw holes. The same filler can be used to add a fillet around the feet and oiler bosses.

Drawing to download for those that are now looking at them

J

[NickG]

Like the look of this Jason, bet it sounds nice. I might even be able to give it a go myself with a few simplified bits as you say. I'll be watching the rest of your build log, thanks.

[Don1966]

Damm Jason, you just make it all looks so dam easy. Still with you mate and enjoying it.........

Don

[NickG]

Hi Jason, when you did the crankshaft I presume you drilled right through for the pins and peined over both ends? Did you loctite the pins? Also, do you know what bond gap is recommended for 648 or do you find a reamed hole fits well with the stock size? I have done a couple of cranks successfully like this for poppin without pins but I never tested how strong they were! I only ask because when I attempted my last built up crankshaft like this, I botched it, the webs moved so I ended up having to jig and silver solder it! I wondered whether there should be a tight fitting location diameter then a bit relieved in the middle for the adhesive but that might all be unnecessary.

[Jasonb]

Hi Nick, good to know I may have tempted you to have a go at this one.

I did not work out any special clearances, just drilled the webs 0.2mm under size eg 9.8 & 7.8 and then reamed. Only imported reamers from ARC which are quoted as H7 which I find work fine for most things.

Pins pass right through with approx their dia sticking out each end, no loctite. Then hammer them over to fill the small countersink and they also expand within the hole. This is another crank before hammering.

[NickG]

Cheers Jason, good looking engine.

[Jasonb]

Piston

At a shade under 24mm dia the piston will come nicely out of a piece of 25mm or 1" bar so pop a bit in the chuck with enough poking out for the part and turn down to the required 23.95mm which will leave a little room for the piston to expand due to the heat if you decide to run on steam.

At the same setting the end can be faced off then starting with a spotting drill most of the waste can be drilled out  to say 12mm before changing to a boring bar to open up the hole to the required 16mm dia by 24mm depth.



The piston ring grooves can also be added at this stage, I have given dimensions from the end of the piston to the left of the groove so simply touch the edge of the parting tool against the end of the piston and then wind the topslide along 8mm for the first groove and 26mm for the second. Bring the topslide back as you make a couple more parting cuts until the grooves are 2.6mm wide. Ease all the external corners so the O rings don't get nicked when fitting.

You will notice that I cut 3 grooves as per Stan Bray's sketch but two will be quite adequate and is what I have shown on the drawings. My engine runs fine on air with just one ring in the groove furthest from the crank.



Over to the mill now, locate the centre of the piston dia, the ruler trick will do and then drill and ream a 4mm hole 17mm from the open end. I don't have many machine reamers but find that a hand reamer held in a collet and run at slow speed works perfectly well and in these sort of sizes tend to drill 0.2mm under dia so in this case drill 3.8mm.



Saw or part off the piston a little over length then with something to protect the finished surface lightly hold in the chuck while the end is faced back to get the final 28mm length.



O-Rings

I used Vitron O-rings: 19.6mm ID x 2.4mm section, bought on e-bay # 371503929586

Wrist Pin

This is just a short length of 4mm silver steel (Drill Rod) faced to 21mm long and with a 2mm dia x 5mm deep hole in each end.

Wrist Pin Pads

These can be from Acetal, nylon, or any other similar material or bronze if you prefer doing them in metal so long as it is softer than the iron so they protect the bore from the wrist pin. Turn a short length to 4mm and then the 2mm spigot and finally part off to give a 1mm thick head.



Drawing to Download

J

[Jasonb]

Conrod

I used a piece of 12x25mm black mild steel bar for this a few mm longer than the finished size. Start by maching one end down to 10x22mm and then the other to 6x10mm, square off the 10x22 end and then drill and ream 6mm dia 80mm from that end.



Put a small BS0 centre drill hole in each end and also drill the two 3mm holes in the big end.



Use a hack saw to remove most of the waste then set up on the lathe between centres, firstly rough the rod down until its parallel and a little over 8mm then set the topslide over and finish to the final taper going from 8mm down to 6mm with a round nose tool.



Finally the small end can be rounded over which wil remove the ctr drill hole

Big End Bearings and Keep Plate

I will describe these together as some of the work can be done on both at the same time.

For the bearings machine two pieces of bronze to 6mm thick and then soft solder together, once cool machine the pair to the final 22mm x 12mm. I find it easier this way than trying to line up two pieces that are finished size when soldering.

The keep plate is just a piece of 3mm thick material machined to 10mm x 22mm.

Drill the 3mm holes and include another small ctr drill hole in the keep plate.



Lightly hold the two bearing halves in the 4-jaw and drill, bore then ream out to 10mm



A small round nose tool can then be used to remove 1mm of material on each side blending nicely into the 12mm dia.



The parts so far can be assembled with a couple of temporary nuts and bolts, held between ctrs and then the big end turned down to 22mm dia and the round nosed tool used again to cut the 20mm dia waist in the bronze. Mark the parts so they can go back together the same way. Unsolder the bearings and give the mating faces a light rub on some wet & dry.



Small End Bearing

This is a straight forward turning job, the bearing can be pressed or loctited into the conrod.

Finally thread the ends of a couple of bits of 3mm rod and add a nut each end to hold things together. Test the fit on the crankshaft as the bearings may have closed up a bit when the solder was cleaned off, if so just run the reamer through again.



Drawing to Download

J

[Tennessee Whiskey]

Hard to believe this kind of work is done on far Eastern machinery    Knowing you, this one is already happily running  , imagine that, a runner 

Cletus

[Don1966]

Nice photos and some really nice work going on in this classroom. Still enjoying it Jason.......

Don

[Jim Nic]

Jason
I've started assembling materials and stuff to build the Jowett and I've printed the drawings so far but I can't seem to get the conrod drawing to download.  Is it me? 
Jim