# Super Newbie - Elbow Engine UHMW, HDPE.



## AssassinXCV (May 30, 2011)

Decided i wanted to try to make an elbow engine. I don't have tools right now to machine metal, but i do have wood working tools. I picked up some industrial grade plastics which have an extremely low coefficient of friction. Since plastic is made from oil, and this plastic that i have is very slippery, i don't think I'll have to use oil for it. UHMW also is resistive to chemicals, and does not absorb moister, so i wont have to worry about expansion.

I Like the look of a 6-elbow engine compared to the 3 elbow version. I've seen 5-elbow engines aswell but I dont think the engine requires an odd number of elbows to work.

I'm going to construct the elbows the same way Arnold did with his engine.



















Tools available: 

- Drill Press.
- Bandsaw with metal cutting blade (wood blade was kinked). 
- Chopsaw. 
- No lathe.
- No mill. 
- Square. 
- Ruler.
- Wood cutting Forstner Bits.
- Counter sink bit.
- HSS Drill bits.
- Bolt Cutters.
- Table top grinder.


Will be going to Harbor Freight to buy mini lathe chuck for my mini cnc machine i'm almost finished. Might pick up one of their cheap metal lathes.


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## AssassinXCV (May 30, 2011)

I cut out the vertical peice from 1/2" thick UHMW sheet. Drilled the holes, and then cut out the profile last. I also tapped holes to be able to mount to the base.


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## AssassinXCV (May 30, 2011)

I then cut out the base from 3/4" UHMW sheet. Drilled out the holes.


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## stevehuckss396 (May 30, 2011)

This is going to be interesting. Keep the pic coming.


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## AssassinXCV (May 30, 2011)

The plastic shop didnt have stock in the 2" and the 2 1/2" Rod that i needed. To order it in from the manufacturer, and the minimum amount would be 12" of each, it would cost me $40 total...UGH!. Looking for other suppliers in the area that might have stock. I did buy 3/8" and 1/4" rod for the elbows; so i can work on that next.


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## steamer (May 30, 2011)

Has anyone a connection with short piece UHMW PE?

Plastics Unlimited in Worcester Massachusetts may have what you want.  You may want to try them anyway....

Keep at it! Your knocking it down.... ;D

Dave


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## AssassinXCV (May 30, 2011)

Hopefully i'll be the first person to build a successful engine using not-so-accurate tools. Reading some of the threads on the completed machines have taught me that this engine can be quite finicky, and that everything has to be perfect, but already it is far from perfect.

Drew out Fly wheel pattern, cutting it up using a bandsaw, not going to be anywhere near precise as what a lathe will do, but i'll have to make do. 

Twelve Pistons; Twelve Holes.


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## steamer (May 30, 2011)

Indexing the holes for the pistons will be tough.  You may want to match drill them together, so any error is duplicated in the other part and hopefully cancelled out......but I haven't built this engine....say guys, who has ?

Dave


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## nfk (May 30, 2011)

Hi,
It will be tough without a lathe but it surely can be done.
I`ll be following your build with great interest, keep the pics coming!

Norberto


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## AssassinXCV (May 30, 2011)

Wow thanks, i appreciate your guys' interest. I'm planning of drilling the cylinder holes into the rod, and then cutting the piece in two.


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## steamer (May 30, 2011)

That is probably very wise.

NOW

I'm assuming you have a drill press?....if so have you checked it for squareness?

I can explain a simple way to at least check squarness without a lot of equipment....like do you have a coat hanger? ;D

Dave


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## AssassinXCV (May 30, 2011)

I think it's square, can't remember if i checked it when i put the chuck on it. Yes, i do have a coat hanger, wire ones and plastic ones.

To bend the plastic rod for the elbows, i made up this guide that i can use in the future too. It wont be nearly strong enough to bend metal, but it will clamp the plastic in place while it cools (The people in the plastic shop said that if i slowly heat up the rod, it will keep it from bubbling and becoming mis-shapen).










The arced lines are where could cut a small grove in to hold the plastic in place while it shapes the arc of the rod.


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## steamer (May 30, 2011)

Cut a piece of coat hanger and straighten it out with your hands.  Grind a point on one end..about 30 degrees...nice and sharp.

Bend the coat hanger into a Z shape ( you may need to cut the length down a bit depending on the size of your DP.  ) and mount it in the drill chuck loose.  The offset in the Z should bring the point to the very edge of the table in all four quadrants.

Cut some writting paper into small squares and put one on each corner...or in 4 diametrically opposed sides if its a round table like mine.

Now between the chuck and some manipulation with your hands, move/bend the "Z" such that it just, and I mean JUST grabs the first piece of paper off the corner. LOCK your adjustments, and don't move anything now other than rotating your drill chuck.

Now turn your spindle to the other pieces of paper....does the spindle move them?...or does it go over them?

If it moves them, carefully drag the piece of paper under the point and FEEL how much it drags...compare this drag with the other 3 positions on the table....they should all feel the same

Adjust the table swivel as required...if you don't have a table swivel.....well, at least you know how far out your are!


Though very crude, this technique with get you within oh .005" or better over the size of the table

If you really want to push this, try using ZIG ZAG smoking paper.... ;D NO NOT FOR THAT REASON

The paper is precisly .0008/.0010.  Makes for cheap feeler guage...This will get your much closer still


Dave


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## AssassinXCV (May 31, 2011)

Found some nylon nuts and bolts for very good prices, now i'll be able to have this be an all plastic engine, not metal at all.

Cylinder rotation:
Acorn Nuts: http://www.fastenal.com/web/products/detail.ex?sku=0184624&ucst=t
Hex Bolts: http://www.fastenal.com/web/products/detail.ex?sku=76094&ucst=t

Vertical part:

Flat Head: http://www.fastenal.com/web/products/detail.ex?sku=76027&ucst=t


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## AssassinXCV (May 31, 2011)

steamer  said:
			
		

> Cut a piece of coat hanger and straighten it out with your hands. Grind a point on one end..about 30 degrees...nice and sharp.
> 
> Bend the coat hanger into a Z shape ( you may need to cut the length down a bit depending on the size of your DP. ) and mount it in the drill chuck loose.  The offset in the Z should bring the point to the very edge of the table in all four quadrants.
> 
> ...



Wow thanks, very interesting, but wouldn't using a machinist's square be better? Just stick a piece of bar stock in the chuck, and check it like that? I'll try it out tomorrow and see what happens.


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## arnoldb (May 31, 2011)

Hi

 ;D Nice work!

Like Steamer said, check your drill press for squareness - this engine does not tolerate anything out of square 

Drilling the cylinders before cutting is the way to go - and mark them to remember the orientation before cutting them apart; going for more cylinders will make things a lot harder to get lined up and running later on.

How are you going to finish the cylinder bores ? - they need to be smooth as silk, otherwise things are just going to jam up all the time...

Good luck with your build Thm:

Regards, Arnold


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## AssassinXCV (May 31, 2011)

arnoldb  said:
			
		

> How are you going to finish the cylinder bores ? - they need to be smooth as silk, otherwise things are just going to jam up all the time...



The thing I've found with UHMW, is that the cut edges are more slippery than the non cut edges, so i'm hoping that will be smooth enough.


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## b.lindsey (May 31, 2011)

UHMW is a nice material and machines well though it does require a lot of deburring. A good sharp reamer should do well on the cylinder bores. I am more concerned about how close you can hold the 90 degree bend in the pistons but it may work out fine. Just from what others have said, this seems to be one of the most critical aspects of this engine. I am following along with interest and wish you the best.

Bill


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## steamer (May 31, 2011)

AssassinXCV  said:
			
		

> Wow thanks, very interesting, but wouldn't using a machinist's square be better? Just stick a piece of bar stock in the chuck, and check it like that? I'll try it out tomorrow and see what happens.




Yes it might be depending on the size of the square...but I was under the impression you didn't have any metal working tools.  Additionally, make sure the piece of bar stock is straight and has no run out, or you may make it worse, not better

Dave


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## steamer (May 31, 2011)

b.lindsey  said:
			
		

> UHMW is a nice material and machines well though it does require a lot of deburring. A good sharp reamer should do well on the cylinder bores. I am more concerned about how close you can hold the 90 degree bend in the pistons but it may work out fine. Just from what others have said, this seems to be one of the most critical aspects of this engine. I am following along with interest and wish you the best.
> 
> Bill



Bill 
Your absolutely right....but he has one thing going for it....UHMW PE is flexable....it may "flex" it's way through some squareness error....getting the pistons to fit,as you stated, without burrs will be real tough....

Dave


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## AssassinXCV (May 31, 2011)

I dont have a good enough camera to show you, but trust me, the walls of the bores i've made on the other parts are smooth as silk, using regular HSS bits.


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## AssassinXCV (May 31, 2011)

Got the Flywheel holes bored and used a counter sinking bit to de-burr the edges.

Will drill out the centre hole once I pick up a 2" Forstner bit. Hopefully the flywheel will have a tight fit over the 2" UHMW rod that I'm using for the revolving cylinders.


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## AssassinXCV (May 31, 2011)

For the pistons, I'm not sure if the ends where they attach to the elbows should be slightly above the cylinders, or completely flush. I'd really appreciate your opinions. Also, do i want the pistons to reach the very bottom of the cylinders or just slightly above?

Thanks.


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## steamer (May 31, 2011)

AssassinXCV  said:
			
		

> I dont have a good enough camera to show you, but trust me, the walls of the bores i've made on the other parts are smooth as silk, using regular HSS bits.




Hi

I'm sure the walls are smooth, but that isn't a guarantee of squarness.  Honestly, I'd try the coat hanger ;D


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## Captain Jerry (May 31, 2011)

steamer  said:
			
		

> Indexing the holes for the pistons will be tough.  You may want to match drill them together, so any error is duplicated in the other part and hopefully cancelled out......but I haven't built this engine....say guys, who has ?
> 
> Dave



I have not built this particular engine but I HAVE built a similar engine using less than accurate machines. I t was not until I came to understand that truly square is difficult to achieve and not really important. The real important factor is parallel and it can be achieved easily on any machine. Do Not! rotate the stock to index the cylinder bores. If you maintain the orientation and move the blank stock into position under the drill bit, then all of the cylinder bores and the center shaft bore will be parallel. It is not critical to maintain the cylinder bores on a precise radius and it is not critical to have the cylinder bores angular offset position absolutely equally spaced. Cheap compass, protractor, and eyeball position is good enough as long as the bores are all parallel. You must mark the cylinder positions and the matching faces when you cut the cylinder blank in two. The only time that square is really important is that the valve faces must be square to the shaft to have a good seal and pressure transfer. It is also not absolutely necessary that the pistons be bent to exactly 90 degrees as long as they are all bent to exactly the same angle. Ninety degrees is a good goal but not as important as consistency.

I am not advocating bad practice and sloppy work but with the tool limitation that you face it is important to keep the important factors at the front. Without a rotary table or other precision indexing method it is almost impossible to drill a perfect circular array. But you can be sure that everything is parallel.

I am more concerned with the stability of the elbow bend after it is removed from the bending jig. Most materials will have some spring back when bent and in some plastics, the spring back can be slow to appear, days or even weeks later the angle may still be moving. I have not worked with this particular material but if it turns out to be a problem, you might be able to stabilize the bend by using a metallic core.

I think that this project can be completed as you plan. I am watching with great interest and moral support.

Best wishes for success
Jerry


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## Captain Jerry (May 31, 2011)

It took me a few minutes to find this but I wanted to show that I have some familiarity with bent-axis engines. This engine has a 72 degree bent axis but almost any angle, including 90 degrees can be made to work.

Jerry

[ame]http://youtu.be/hOOzFG1canw[/ame]


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## steamer (May 31, 2011)

Capt,

Parallel to what ...each other?

Won't they need to be parallel to each other in both planes?
 ???

Dave


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## Captain Jerry (May 31, 2011)

Dave,

Thats exactly what I mean. If the holes are drilled without rotating the stock about its center, then all holes will be parallel in all planes. Even if there is a slight misalignment from square of the spindle/table. on the other hand, assuming that there WILL be some misalignment, if the cylinder stock is rotated around a central axis to locate the cylinder locations, the error will be doubled, not cancelled.

I hope I am am making this clear, but probably not. I will make an illustration if it would. My Crap-O-Cad system is down so I'll have to resort to something else.

Jerry


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## AssassinXCV (May 31, 2011)

Thanks for all your suggestions, hopefully they will do me some good.


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## AssassinXCV (Jun 1, 2011)

Now ain't that a beautiful, super precise flywheel... :-


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## steamer (Jun 1, 2011)

Looking good!

Dave


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## AssassinXCV (Jun 1, 2011)

Thanks. I was wondering which would be the best way to mount the Flywheel to the cylinder column. The column is 2" diameter, should i buy a cheap 1 15/16" forstner bit to bore out the flywheel and provide an interference fit? Or should i use a 2" diameter bit?


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## Tin Falcon (Jun 1, 2011)

Early am here. I did not read all the posts so could be missing something. first of all you have a hole for the intake exhaust ports. you need to machine a crescent for each the space between the two needs to be a bit bigger than bore diameter. 
Second it looks like the jig you set up allows for different length pistons you only need one length. 
Again if I repeated something or am missing something sorry.
Tin


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## Captain Jerry (Jun 1, 2011)

Mr XCV (or can I call you Assassin?)

I would get the material before deciding on the bit and be sure of it actual diameter. Then instead of a Forstner bit bit you might try an adjustable circle cutter. The kind with a pilot bit and an adjustable beam that holds a HSS tool bit. Those things work great on HDPE. I have used them to make instrument panel cutouts in marine applications with great results. Fitting the flywheel to the cylinder needs some thinking. A 1/16" interference fit might put enough pressure on the cylinder to compress the cylinder bores. On the other hand, I don't know of any adhesive that will work on HDPE. It might need some kind of mechanical fastener, pins or screws.

Jerry


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## ddmckee54 (Jun 1, 2011)

Going back to the cylinder bores for a minute, couldn't you drill them oversize and sleeve them with thinwall brass tube from the hobby shop? It's available in a boat load of sizes, should satisfy the smooth as silk requirement, and should press into the UHMW fairly easily.

Just a thought,
Don

Long time lurker


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## AssassinXCV (Jun 1, 2011)

Tin Falcon:

That jig is just for the elbow parts of the pistons, i just bend the 1/4" rod, and then drill holes into the 3/8" rod, and push the 1/4" rod elbows into the 3/8" pistons.

Captain Jerry:

There is no glue capable of gluing UHMW together, that's why i chose this stuff, since it has machining properties of Metal. It can be welded though. If i can't weld it (testing with scrap pieces) then i'm thinking i could put some slices of tubing on either side of the flywheel and using some set screws to fasten it.

I do have one of those hole cutter kits, where you take out all the blades except the size you need. I also have a 2" on its own cutter, but it isn't accurate enough compared to the clean edge that a forstner bit will cut.

Gotta get back to it,

Ian


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## AssassinXCV (Jun 1, 2011)

Completed jig for elbows:


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## AssassinXCV (Jun 1, 2011)

Elbows to attach to pistons


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## Captain Jerry (Jun 1, 2011)

AssassinXCV  said:
			
		

> Captain Jerry:
> 
> I do have one of those hole cutter kits, where you take out all the blades except the size you need. I also have a 2" on its own cutter, but it isn't accurate enough compared to the clean edge that a forstner bit will cut.
> 
> Ian



Thats not the kind of hole cutter I was thinking of. Those are just a hole saw and the cut is pretty ragged. I was thinking of a beam type fly cutter like the one in the attachment. It uses a single HSS cutter and can produce a fine finish if properly sharpened an used in a drill press at the correct speed. Its primary advantage is that the radius is infinitely variable, like a boring head. It can produce a hole that exactly matches the diameter of the cylinder, even if the cylinder stock is slightly over or under. 

You are right about a forstner bits ability to produce a fine finish but the hole is one size, take it or leave it.

Jerry


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## AssassinXCV (Jun 1, 2011)

Completed the elbows and pistons, they work with press fit since they're really tight, so no glue or plastic welding required.
THe good thing with UHMW is that it has a very low melting temperature, i can pull out a cigarette lighter and make angle adjustments to the elbows as i need to.

How tight the 1/4" rod fit into the 1/4" counterbores in the 3/8" rod means that i will need the holes in the cylinder blocks to be slightly larger than 3/8".


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## b.lindsey (Jun 2, 2011)

Looks like they tunred out well Ian. Still following along.

Bill


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## winklmj (Jun 2, 2011)

Looking good. I'll keep an eye on this build.


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## AssassinXCV (Jun 2, 2011)

All that's left to do are the cylinder blocks and the valve blocks, and that requires 2" and 2 1/2" rod.


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## ShedBoy (Jun 2, 2011)

Interesting build you have going here, keep the pics coming.
Brock


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## AssassinXCV (Jun 7, 2011)

Found another plastic store with better pricing; 2" for $9.30/foot. THey dont have 2 1/2", so the next size up is 3" and that's $24.90/foot <--- *bang*

Here's what it will look like with only using 2" rod; should work fine enough.

                          2 1/2" Rod                  2" Rod
                             |                      |
                             |                      |
                             |                      |
                             V                      V


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## AssassinXCV (Jun 9, 2011)

Finally got the UHMW  2" rod, 13" long only cost $9.97

Awesome quality photos


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## AssassinXCV (Jun 10, 2011)

Machining hole in flywheel:






Cuts like butter:






Smooth:


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## AssassinXCV (Jun 10, 2011)

Used chop saw to cut out the valve blocks and cylinder blocks:






I got to excited that i can finally cutting the 2" bar, that i forgot that i wanted to wait to separate the cylinder bar into two, but i know of a way to keep them lined up.


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## AssassinXCV (Jun 11, 2011)

Peck drilled out some of the valve, then used a box cutter (xacto knife) to cut out the rest of the shape. Counter sunk the bolts mounting the valve block to the base.





Penny for scale.

What it'll look like with the cylinder blocks:






As you can see, i have not drilled them out...yet.


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## AssassinXCV (Jun 11, 2011)

Drilled out Cylinder blocks at 25/64". The pistons are 3/8" (24/64") so that gives me 1/64" of forgiveness.






PISTONS FIT AND SLIDE NICELY!!!!!










I'll have to shorten some of the pistons since they hit the valve block. Check previous screenshots.

Almost finished!!!


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## AssassinXCV (Jun 11, 2011)

:'( It's a sad, sad day. The pistons worked when they weren't bound to the axles, but when i mount the cylinders to the base, the whole thing jams up. :'( Too many inaccuracies, since i dont have a lathe yet. I sprayed some WD-40 but it didnt help much. I'll see what i can do to find out what the worst part is and do what i can to fix that.


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## steamer (Jun 11, 2011)

Well, the fact that it doesn't run right away is nothing new to the members of this forum,,,we've all been there..

Don't give up yet....keep at it.

What's binding specifically? Can you isolate it?

Dave


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## AssassinXCV (Jun 11, 2011)

Okay so i remeasured the pistons lengths and it turns out they're around 1/8" too long. It's because the elbows must have not been pushed far enough into the pistons. I just cut them down to the proper length, will be testing some more.

EDIT: Okay, it improved, but it is still pretty stiff, will check square-ness of elbows/pistons. A bit of sanding to square up the bottom of one of the cylinder blocks, and it should rotate better.


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## steamer (Jun 11, 2011)

Ah NOW

If your going to sand, put the paper on a flat steel block.  You'll get flatter surfaces that way.
BE PATIENT!  you want to take small amounts of materail off and maintain a good surface finish while you do it

Dave


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## peter cook (Oct 23, 2018)

Hi all.  My second post here in HMEM.  Nice build.  Did the OP ever finish this build?


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