Potty Dake Engine

[sbwhart]

Cheers Guys 

Time for a progress update.

Made the side slipper bars for the piston I had some suitable brass bar in my stash.

Square it up and bring it to size.



Drill and mill the slots



And then it was  :doh: time I must have got one of the co-ordinates wrong for drilling as a result it was off set 1mm.

Rather than waist it decided it would come to no harm if I mounted the assembly in the four jaw and skim things level.





I think that came out better than the origonal, it 0.5mm thinner than I intended but that won't do any harm



Next part the outer piston/cylinder this part has a duel function it forms the cylinder for the inner piston, and also does duty as the outer piston.

I'm making this out of 5/16"*1" mild steel bar, first cut the bits off to length, then for the two side peices that the inner piston will work over, with them clamped together fly cut a light skim off, this takes care of the slight bend that was in the bar.



Keeping the parts in the vice so that the step at both ends is exactly the same as this helps to get a square assy, the vice was swiveled round 90 deg and the bar clocked level, doing it this way I could take advantage of the power feed.

Then mill the step to the same depth and to the correct width.



With this done the parts can be removed from the vice
Swivel the vice back and clock it square, and drill the holes and slot set the vice stop



Flip it over with the same edge against the stop and counter sink the holes.



Thats another bit done.



Stew

[Don1966]

Wow!! It's is a pleasure to follow along with you Stew. That is some great setups.

Don

[Captain Jerry]

Stew

Thanks for sending the plans.  I am following and learning.  I like the way you have fabricated the inner piston and incorporated the slippers into the form.  Do you think that the weight of this piston is going to create a balance issue?  In Dake's original, the inner piston shows a lot of hollow space that I thought might be an effort to reduce weight.

Jerry

[sbwhart]

Thanks Don

Stew

Do you think that the weight of this piston is going to create a balance issue?  In Dake's original, the inner piston shows a lot of hollow space that I thought might be an effort to reduce weight.

Jerry

I don't realy know Jerry if it will be an issue, the only model I can find had a similar design and that seems to work ok.

I'm a bit concerned about the swept volume of the pistons it will certainly gobble up air, its such a strange design its dificult to predict what will happen, from what I can find out it wasn't a high reving engine but it delivered a lot of torque.

Stew

[sbwhart]

Finished off the outer piston today.

Squared off the ends, and brought both sides to exactly the same length, had to take it steady as there was quite a bit sticking out.



Then drilled and tapped M3



Screwed it all together with stud lock.



Then over on the lathe in the four jaw skimmed both sides level and to size, had to make sure I was level in the jaws by taking a cut and checking that it was the same size all round, and adjust with a light tap.



I made the width just 0.05mm smaller than the inner piston.

Mounted the inner piston on the mandrell in the spinidexer and skimmed down each side to give a nice slide fit in the outer, doing it this way ensured it was cimetrical.



The outer piston slides in the outer casing, the sliding face needs to be square to the inner sliding face. So clocked the inner sliding face level on a angle plate.



Flip the plate 90 deg and skim up the outer sliding face.



Its an easy job to get the other face square and parallel by just sitting the good face on a 1*2*3 block and giving it a skim.



Quite pleased how that turned out.



The outer piston still needs the reces machining for the flange but I will do that when its assembled into the outer frame.

Stew

[tvoght]

Stew,
I've been right on top of this since you started the thread. I'm completely enjoying the build. It seems there is a prototype Dake running on compressed air at a steam museum here in Indiana. I'd like to get up there and see it (well the whole museum, for that matter).

--Tim

[ozzie46]

  Stew, Your ability to take these odd looking engines and model them, seemingly, with ease is astounding.    Great work.

  Ron

[NickG]

Glad I've found this Stew - am not sure I fully understood it when I saw the drawings round at yours not long ago! Great to see you make a start on it, i'll definitely be watching! 

[zeeprogrammer]

  Stew, Your ability to take these odd looking engines and model them, seemingly, with ease is astounding.  Great work.

Says it all for me.

[Don1966]

Love the progress Stew, I agree with everyone. Superb job in every sense.

Don

[sbwhart]

Thanks for the support and interest Guys

I had to redraw the back plate mainly because I made the outerpiston from thicker 5/16 plate this would impact by reducing the clearance at the end of the stroke to 1mm so decided to increase the width of the plate to accomodate this change, also I realised that by not having adjustable jib strips I was changed the over all shape off the engine, so decided to increase the height so that it would look as though ut had jib strips fitted.

A made the back plate from some scrap yard 16mm thick ally jig plate.

First op square the plate up to size.



With the dro I find it easyer if everything is dimentioned from a common centre point also with my digital height gauge this also makes marking out easy.

Just zero the height gauge on the centre point, then you can make adjustments up and down to bring it on the size you want.



Just as a sanity check I centre poped the positions as an insurance I'm drilling in the right spot.

Set the plate up in the mill on some parallels so that I wouldn't drill into the table, and with a stop set up square to but the plate up against.

Find the edges of the plate and Zero the DRO on the centre point, first drilling op centre drill the zero position so that I have a datum point off set and centre drill for the bearing housing position, then using the PCD feature drill and tap 6 stud holes M4, and on the bearing centre line drill the edge of the plate to take 2*3mm dowels to aid alignment with the covers ets.




Then it was just a matter of walking round the edge to each poistion to drill M4 clearance and counterbore with a 5/16 slot drill to take the stud pads that will be fitted later.



The plate was too big to do all around it at one setting, so unclamp reposition and using a centre wound into the datum point and with the plate up against the stop, reclamp zero the dro on this new position and finish off the rest of the holes.





So far so good.



Now to maching the hole to take the bearing housing.

With my big four jaw independant chuck in the lathe with a wobble bar set up in the centre clock it up true to get position.



Just a matter now to put a bigger centre in the job drill the meat out then finish off to size with a boring bar.



Job done.



Still needs the bolting pads fitting and the edges rounding off so that it looks more like a casting, but I'll do that at final assy.

Stew

[Bearcar1]

Just superb. I really do enjoy watching you work Stew, so orderly. It's shaping up to be another very interesting engine when completed. Cary on  .


BC1
Jim

[sbwhart]

Thanks Jim

The clamp holes and exhaust port for the front plate was machined up excatly the same as for the back plate.
For the anular inlet port I machined up a mandrel for a nice fit on the exhaust port.



Then mounted the chuck on the RT centred it under the quil and machined the port with a 3mm slot drill.





As a sanity check I tried the alignment of the dowel holes in the front a back plates.



Spot on  :thumbup:

I need to wait for the delivery of a 4mm long series drill before i finish of the front plate, so made a start on the bearing housing.

This is made from some 2 1/4" ally bar.

Face a centre drill then using a running centre machine down the OD. then drill through and bore out for the ball bearing pocket.



Swap in round in the chuck and protecting the finished dia with a strip of drinks can part off excess.



Clock up the register diameter.



And bore out the pocket for the other bearing.



Keping the job in the chuck swap over onto the mill and using that clock thing centre the quil up on the bore.



And drill the 6*4mm on the correct PCD.



And this is where it fits.



Another bit done.

Stew

[Dan Rowe]

Nice work Stew.

Watching this engine being built from the inside out is really interesting.

Dan

[Don1966]

Wow! your moving right along there Stew. Man that is some nice setups. Still following with interest and enjoying it. 

Don