Elbow Engine

[sbwhart]

Well I'd started two elbow engines No 1 has resided on the desk where I absentmindedly give it a turn now and then, as for No 2 that was never finished off, and its spent the time on the back shelf of my shop, but I have been on the look out for material to make the flywheel from, I've pick up quite a few short pieces of brass tube about 1" long and 3 to 4 " dia and some 1/4" ally plate, so its time for No 2 to be finished off I'm planning to add a bit of novelty to this one:- so here we go.

First job clean fly wheel rim and bore.



Bore cleaned to leave a 1mm step for the hub to but against.

The hub is made from 1/4 " plate rough cut to shape with a centre roughly in the middle then some masking tape stuck on the back for friction turning.



Grip a stub of bar flush with the jaws of the chuck.



Trap the piece of plate between the running centre and the chuck and with light cuts skim up the OD to give a nice neat fit in the rim.



Now I'm going to cut the spokes in the hub using the RT and and the PCD feature of the mill DRO.

First stub of bar in the chuck to lift the hub clear of the chuck jaws.



Grip the hub in the chuck with the RT still lose on the table centre the RT with the quill by holding a centre tight into the centre in the hub, then tighten the RT down.



I drew out the the hub in cad and put a few critical dimensions on the drawing to guide me. Then using a combination of the RT and the PCD feature of the DRO drill corner holes 5 mm.



Then using a 5mm slot drill joined the holes up.



Then repeat for the inside.



Then join the two parts up



And thats it spokes cut in the hub they need a bit of a tidy up and the bore opening out for the cylinders but that jobs for another day.



This is what it looks like in the rim with the cad drawing.

Have fun

Stew

[Stilldrillin]

Nicely done & shown...... Again, Stew! 

Another runner, in no time. 

David D

[Bernd]

Nice looking flywheel Stew. 

Bernd

[NickG]

Nice work Stew, couple of good centring tricks i have learned there.

Nick

[sbwhart]

Thanks Chaps

Added some novelty features to the cylinders.

Set up in the indexer on a mandrel and getting the bores on correct alignment with the aid of a height gauge.



Then with a 1/4" ball noses slot drill mill some scollops into the cylinder



The picked up the bores on the rotary table and added three more 1/4" blind holes, sorry no pics. Pop some 1/4 ball bearings into the blind holes, and this is what you get



Now what do they look like.
 


Have fun

Stew

[Bluechip]

Hi Stew

Very nice looking engine, followed with some interest. Now, I know what I think they look like, so, before you get arrested, ..

How does the ally bit stay inside the brass rim ? Shrink fit? or what?

Dave BC

[sbwhart]

Dave

I'll be using good old high strength loctite thats what's holding No 1 together, its not moved after quite a bit of 

Cheers

Stew

[madjackghengis]

Well Stew, every time I watch someone work on an "elbow engine", I reflect on the actual forces that are enacted through the two cylindrical sets of cylinders, and consider my work on hydrostatic drives sufficient for my own purpose when it comes to elbows.  Having just rebuilt a few hydrostatic drives for lawnmower and woods maintenance equipment, you may know that I am watching with eagerness, hoping you will come out with an engine that spins freely and at high speed in the end, and brings out the least number of curses.  I've seen a stirling engine built on the same principle for the expanding cylinder, but at about a thirty degree angle rather than a right angle, and I believe it is because the lower angle gives a better leverage ratio and less friction loss, but at the cost of pressure and power in the stroke.  Popular Mechanics had a version it published back in the sixties or early seventies, where there was a hinge joint on each of six sets of pistons/rods, and while I believe the claim it ran great, I am still at a loss as to how, without binding up completely.
     Watching with baited breath, looking forward to seeing that engine run :beer:Mad Jack

[sbwhart]

Jack

Elbows fascinate people, they look deceptively simple to make but as you say a bit of a beast to get running, I was lucky with No 1 it ran first time of trying although it had some tight spots, still has, you need to get everything dead square which is easy said than done, I'm keeping my fingers crossed that No 2 will be a runner.

Thanks for your interest.

Have fun

Stew

[Bluechip]

Dave

I'll be using good old high strength loctite thats what's holding No 1 together, its not moved after quite a bit of 

Cheers

Stew

Tks Stew, have now taken the opportunity to go through the whole thread. Something I should have done in the first place.

They really are a curious device. But, when the one on Bogs Vid. slows down, either strobing or whatever, you can just about see what's going on. I wonder how the originator came up with the principle?

Far too precise for me to attempt. After yesterdays antics, anything is 

Might as well confess, drilled a hole in a transformer... greatly improved the cooling, electrically it is done for. Ah well, order to Farnell tomorrow...


Dave BC   

[sbwhart]

Thanks Dave

Hard luck with the motor 

By way of a confession I scrap a cylinders when drilling a hole for the ball bearing, so made two new ones, I didn't take any pics but I tried a new idea out to make them.

I chucked the bar up with enough material sticking out to make two cylinders, skimmed down the OD and drilled the centre hole, then transfered the chuck with the bar in place over to the mill, used the trick of having the chuck lose and centring to the quill with the hole using a centre, then clamping the chuck up, then used the PCD feature on my DRO to drill the rest of the holes drilled right through both cylinders, transfering the chuck back over to the lathe, parting off the cylinders, its given me cylinders that have bores that are dead in line with each other in any position, hopefully they will work great.

Cheers

Stew

[madjackghengis]

Stew, I've been considering the forces at work in these elbow engines, mostly because I've seen one with the pistons hinged, actuallly run, yet the majority of the story is if there is the slightest detail in alignment off, they are locked up.  What I've come up with is this:  if the pistons move in and out no more than their diameter, and if the piston remaining in the cylinder is more than twice the diameter long, they can be hinged as the bearing surface remaining in the cylinder is sufficient to keep the two pistons in full alignment.  In some of the hydrostatic motors I work on, the pistons are at least three times the length of their working stroke, while those which have the stroke and bore less than this ratio invariably use balls for pistons, as the ball generates no twist or leverage against its self as a piston would, if cocked in the cylinder as out of square by any means would entail.  I think with this understanding, I am soon to try my hand at an "elbow engine", even just to put on my wife's chair side table to keep her occupied and not yelling at me to do something useful.  I've been considering that elbow engine I saw work forty years ago with hinged pistons, and had to come up with a rational explanation on how it could work, and only just realised all the conditions necessary for such a thing.  Great job on the engine, it's good to see something work the first time out, and so often it takes weeks to work out the bugs.  Cheers :bugeye:Mad Jack

[sbwhart]

Hi Jack

Thats some interesting ideas you've floated there, I toyed with the idea of having an hinged elbow using rubber, the sort of stuff they use for suspension bumpers on cars.

Cheers

Stew

[rleete]

Nice cylinders.  Wish I'd thought of it.

[sbwhart]

Thanks Rleete

This ones going on fleabay so I wanted to make it a little bit special.

Finished off the fly wheel fastened the hub to the rim using heigh strength loctite let it do its curing thing for a couple of hours, then set it up true in the lathe and bore for a nice fit on the cylinder.



Again fastened cylinder to the fly wheel with loctite, this is what its looking like.



Made a start on the base I'll already got it cut to size and some holes drilled, so made a start drilling the long 1/8" dia air ways with a long series drill.

This is the set up I use a little complicated but I want to keep every thing aligned.



And this is what happens when you rush, the drill broke leaving a bit in the job, nothing for it but to start again.



Decided to call it a day.

Our daughter is due to give birth any time to our first grandchild so I'm a bit on edge.

Have fun

Stew

[Stilldrillin]

That`s looking very good Stew! 

1st grandchild? I know just how you feel, though I`ve had 5 weeks practice now!   

Hope all goes well for you and yours......   

David D

[sbwhart]

Thanks Dave our daughters due date is today so we're on tenderhooks.

Any way got some more of the base done today.

Drilling some holes I like to do this job on the angle plate so that I can keep everything lined up its how I did No 1 and that seemed to work OK.



Shaping the vertical support on the RT



Not looking to bad.





Just a few minor bits to do and bend the elbows then It will be fingers crossed to see if she will run, then a bit of a polish.

I've deviated quite a bit from the John Tom drawings changed it with some of Bogs' ideas along with a few of my own.

Thinking of drawing it up with the changes and posting the drawing on her would you guys be interested in that ?.

Have fun

Stew

[madjackghengis]

Hi Jack

Thats some interesting ideas you've floated there, I toyed with the idea of having an hinged elbow using rubber, the sort of stuff they use for suspension bumpers on cars.

Cheers

Stew

Hi Stew, the first such "elbow engine" I ever saw, was in Popular Mechanics as a machining project, back in the late sixties, and it had six cylinders or twelve depending on how you count them, each piston had a ball machined at the connecting end, with the corresponding two ball ends either halved with a pivot pin, or tongue and grooved hinged, with cylinder diameter of about half an inch, and probably seven or eight inches square and tall.  It was shown running, although still pictures don't do justice to such, yet for going on forty years, every single one I've ever seen which tried to emulate this engine with unfixed pistons has been given up as a loss, and redone with the pistons made one piece for both ends.  It has only been the constant stream of these engines showing up in my life, and recalling that one which has brought me to finally focussing on the issue, and recognizing the reason for the failures.  Now I have an obligation to get through my radial engine sooner, so I can actually put in practice, that which I have declared as true, because until it is in metal, it is just theory, not fact.  I am extremely gratified you have managed to be so successful so quickly, and apparently easily, in getting it going with so little re-work.  Great engine ,great inspiration. , thanks, Jack

[sbwhart]

Thanks Jack for your positive comments, I get a lot of inspiration from great forums like this I keep getting infected with  .

Final bit of assembly work today:-

Bent the elbows using a gas torch and a couple of bending rods, then bent them close to square against a 1*2*3 block, and got them dead square by first clocking my vice jaw up true, then set the elbow up on a parallel and clocked it up and gave it a few final tweaks to bring it dead square I got them to within 0.001" run.



Then carefully measured the engine and calculated to determine the length of each arm of the elbow.



Then set them up in the mill and cut them back to give 0.5 mm clearance.

I use a three part axle pin, so that I get dead square shoulders and it makes it easy to measure up the thickness of the cylinder and to trim the pin off to 0.05mm longer than the cylinder, you can see them in this pic



Assembled the engine up and this is what it look like, I still need to bling it up a bit radius the base edge, I may make a wooden base.



And yes it does run 

I'll post a vid after the final bling.

Have fun

Stew

[Stilldrillin]

It ran 1st time?!! 

Yer getting a bit good at this lark now........ 

Well done Stew! 

David D

[NickG]

Fantastic Stew. This is definitely the post anybody trying one of these needs. Hope you get a good price for it, looks excellent.

NIck

[Bernd]

Excellent Stew. 

I think that indicator alignment you showed did the trick so it would run the first time. 

Bernd

[sbwhart]

Thanks again for you comments guys.

Test run the engine in comparison with No 1 engine this one runs a lot better, it keeps running for twice as long with a full tank of air. I'm going to have to have a good look at No 1 and try and get the same performance from it.

Finished the bling work, I don't like thing over done with shine, its a personal thing but to much polishing makes them look like they've had melted chocolate poor over them, not as there is anything wrong with melted chocolate, but not over an engine, I like them to look crisp and honest looking.

Any way hers a pic of No 1 and No 2



And a one for the album



And her,s the video.

I'll crack on and get the drawings completed which will be next week some time.

Have fun

Stew

[Rob.Wilson]

Nice one Stew  Two very fine engines , great work

Cheers Rob

[Stilldrillin]

What a super pair of brothers Stew!

No2 sounds almost like a turbine, after dusting......  

Would that dusting stuff work on my stiff joints?  

David D