# Dusting off my old scratchbuilt engines making them run again.



## hobby (Sep 15, 2018)

I'm dusting off my old scratch built air powered engines and putting them back into running condition again.
These engines were designed and built about a decade ago.

I'l call this engine #1 for this video series.

This is probably the 3rd engine I built after I got the hang of machining parts to make running engines.

Here is a video of it running.



and some pics:


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## tornitore45 (Sep 17, 2018)

Good plan.  Most of the engine we build are run a couple of time to prove ourselves it runs an put away.  I have the same plan, after finishing the current build I am going to run them all.


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## Anatol (Sep 17, 2018)

Cute engine. It seems like it has dual poppet valves on each cylinder? are they driven from 4 cams on the crankshaft, via pushrods? It w0uld be nice to see a closeup of the rockers, and a pic of the crankshaft. It looks like you could adjust the angle between the cylinders (?) Why did you settle on that angle?


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## hobby (Sep 18, 2018)

Anatol said:


> Cute engine. It seems like it has dual poppet valves on each cylinder? are they driven from 4 cams on the crankshaft, via pushrods? It w0uld be nice to see a closeup of the rockers, and a pic of the crankshaft. It looks like you could adjust the angle between the cylinders (?) Why did you settle on that angle?



Thank you,
Yes, I'm using 4 eccentrics to supply the cam action
I think the angle is around 45* included, I chose it mainly for asthetics, it gives a nice Vee look to it.

The crankshaft is built up.
Here is the crankshaft, and the eccentrics:











and the rocker arm assembly:





















Here is a short video of the parts moving under manual control slowly spinning the flywheel by hand.



............................................................


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## hobby (Sep 18, 2018)

tornitore45 said:


> Good plan.  Most of the engine we build are run a couple of time to prove ourselves it runs an put away.  I have the same plan, after finishing the current build I am going to run them all.



Thank you, 
yeh it needed a lot of dusting off, but after a good cleaning and some machine oil the old engine runs like new again.


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## Anatol (Sep 18, 2018)

Thanks for the new pics and video - very nice!


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## olympic (Sep 18, 2018)

A nice, unusual engine. Good work!


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## Jmccrack (Sep 18, 2018)

Very nice. Where did you get the plans for this one?


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## hobby (Sep 18, 2018)

olympic said:


> A nice, unusual engine. Good work!



Thank you!


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## hobby (Sep 18, 2018)

Jmccrack said:


> Very nice. Where did you get the plans for this one?



Hi, thank you!
I didn't have any plans for it, it's scratch built, I was designing it as I was building it.


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## Jmccrack (Sep 19, 2018)

Nice job


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## hobby (Sep 19, 2018)

Jmccrack said:


> Very nice. Where did you get the plans for this one?





Jmccrack said:


> Nice job


Thank you.

When you mentioned plans, I didn't have any plans from another source, but I did draw up my own plans, as I was building it. After you mentioned about plans for this, I looked through my cad files to see if I could find them for this engine, and I found them.

If you want I could load them into this thread, However a word of caution (I cannot guarantee any accuracy on the dimensions or even the drawings, as my method involves deviating away from my plans as needed, and most of the time I don't bother updating the plans to reflect the changes, some of the drawings are just conceptual dimensions, all thrown together to get me in some direction for machining the parts.)

However if your interested in looking over them to see what is feesable and whats not, your most welcome to have them, let me know and I'll upload them into this thread.


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## Jmccrack (Sep 19, 2018)

That would be fantastic. I love the sound. If you have any notes on the build I could email you as well.


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## hobby (Sep 19, 2018)

Hi, I would like to keep everything on the forum here,
however before I upload any of the plans for this, here are some more pics.

These are areas on the engine that I have no dimensions or any design notes on
placement of these parts, they were all done through trial and error.

Here is an example of problem solving, that needs to be done.

the push rod tubes need to be as parrallel as posible on the eccentrics on the crankshaft,
 but need to exit through the top cover of the engine at an angle so as to end up in the 
right place to meet with the rocker arms, it requires taking measurements to know
what compound angle you need, than making a jig to hold the push rod bracket
at a compound angle to drill through.

here the tubes (push rods) are sitting very close to parallel to each other as possible.





exiting the top cover they end up at an angle to each other.





full view





front view





coming back the other side










the angles arrangement of one of the cylinders










As you can see there is a lot of things that you need to figure out on your own, that 
I just don't have any dimensions or design steps to show, it all has to be built by
your own instincts of problem solving in mechanical design.

I'll still upload the plans, I drew up, in the next few days, but again the drawings are more conceptual thoughts
than actual build dimensions, on most of the areas.

If anything, the whole upload would be a good way to get the idea of the build of this engine, but I wouldn't
machine any parts according to the plans, until each part dimension is thoroughly looked over.

Please understand
I'm not trying to discourage you, but I am alerting to you, these plans are not plans I would put out for the forum to build off of, because they were done through trial and error, and this engine is built on ones own ability to do problem solving.

I'll upload the plans next time.


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## hobby (Sep 19, 2018)

*Please do not trust these plans, they were done on the fly, check and recheck all dimensions*
*before committing to machining any parts on these plans.*

*These plans are not uploaded to be used in a build for the forum, if you do you*
*are under your own discretion to use them for a project build.*


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## hobby (Sep 19, 2018)




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## hobby (Sep 19, 2018)

The rest are a bunch of drawings scattered, that I collected, these are just 
conceptual ideas, and work arounds trying to figure out angles and placement of components and such.


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## hobby (Sep 19, 2018)

If I find any more I'll upload them.


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## minh-thanh (Sep 20, 2018)

hobby said:


> Thank you.
> 
> When you mentioned plans, I didn't have any plans from another source, but I did draw up my own plans, as I was building it. After you mentioned about plans for this, I looked through my cad files to see if I could find them for this engine, and I found them.
> 
> ...



The way you do it is the same way I did with my engine  !


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## hobby (Sep 20, 2018)

minh-thanh said:


> The way you do it is the same way I did with my engine  !



I don't think I could design engines to the degree I made them, without my CAD programs.
Yet there are people on this forum, who still use drafting boards to do there designs,
To me that is amazing, my hats off, to those who can design mechanical engines without
CAD programs, it must take years of experience and know how to pull that off.


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## Anatol (Sep 22, 2018)

Thanks for posting drawings. I was going to ask about the valves. I see (I think)  you used a piston type valve for inlet and a poppet type for exhaust. Can you explain why you made those choices?
thanks!


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## hobby (Sep 23, 2018)

Anatol said:


> Thanks for posting drawings. I was going to ask about the valves. I see (I think)  you used a piston type valve for inlet and a poppet type for exhaust. Can you explain why you made those choices?
> thanks!



Hi, That is a very good question,
I had to look through the drawings to see why I did it that way, I was woking with a 1 1/8" dia. round bar for the cylinder, with I think a 3/4" bore.
I wouldn't have enough room for both valves made the same way to fit the bore dia.
So I offset the entire cylinder head with the cylinder to accomodate the intake valve and exhaust valve, so the exhaust valve port and intake port can fit inside the inner bore.

Here are some drawings to show that:


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## Anatol (Sep 24, 2018)

Thankyou for explanation and drawings. I see the space problem. 
Why did you decide to make the inlet the piston valve and the outlet the poppet? 
I can see how/why the exhaust valve lifts - pressure in cylinder I guess, but how/why does the piston valve lift? Is there a spring in the bottom, not indicated in the drawing? 
What did you make the valves and seats from? (I guess you're running on air so not so critical as steam?) How did you seal the piston valve? - Rings? or is it just  close fit? 
Sorry for the probing questions but I'm really interested in this 
thanks!


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## hobby (Sep 24, 2018)

Anatol said:


> Thankyou for explanation and drawings. I see the space problem.
> Why did you decide to make the inlet the piston valve and the outlet the poppet?
> I can see how/why the exhaust valve lifts - pressure in cylinder I guess, but how/why does the piston valve lift? Is there a spring in the bottom, not indicated in the drawing?
> What did you make the valves and seats from? (I guess you're running on air so not so critical as steam?) How did you seal the piston valve? - Rings? or is it just  close fit?
> ...



Hi,
The valves were just a matter of choice, I don't think they had anything to do with performance, that I can recall, I went with the inlet being a port hole into the cylinder, mainly because of other engines I built using piston valves for both intake and exhaust.
I probably could have used a piston valve for the exhaust as well, but I think I was under the impression that a poppet valve would give more seal under air pressure in the cylinder during a power stroke, other wise it is possible for the air to escape past a piston valve, when the cylinder is under full pressure. A poppet valve has an inherent way of sealing up the porthole.

Both valves are spring actuated for lifting, the springs are contained in the top of the cylinder head,







 the spring retainers slip over the stems of both valves, and tightened on with set screws, with the springs bearing against the underside of the retainers.







The valves were machined from 12L14 steel, and I used I think a large center drill, or countersink, or I made a tooling, to machine the seat for the exhaust valve.
The seat is just machined into the cylinder head.

No sealing was necessary for the valves, in fact I think I had to put a small bleeder hole at the bottom side of the inlet valve housing, so as to allow air to bleed through as the piston valve was depressed into its cylinder, otherwise the piston fit of the valve made it difficult for the rocker arm to push down on the valve, thereby stopping the engine cycle.

The pistons were machined for piston fit to get the greatest amount of compression on the power stroke, but later I had to take the diameters of the pistons down, because if you don't allow some blow by of air past the piston, then the piston will be forced down very hard on the power stroke, and usually does not have enough flywheel momentum to return back up, stopping the engine, so when that happens, the piston needs to be reduced very little until you get smooth flywheel action. In this case piston rings would not be feasible. 

No need to apologize, I am happy your interested in this project, I am glad to help out as much as I can.


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## Anatol (Sep 24, 2018)

"for lifting, the springs are contained in the top of the cylinder head,"

ok, so the valve stems are positively pinned to the rockers. I missed that detail. 

" ...I had to put a small bleeder hole at the bottom side of the inlet valve housing, so as to allow air to bleed through as the piston valve was depressed into its cylinder,"

yes, I saw it in the drawing. 

"then the piston will be forced down very hard on the power stroke, and usually does not have enough flywheel momentum to return back up, stopping the engine,"

right - unless a  heavy flywheel.

thanks again!


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## hobby (Sep 25, 2018)

Anatol said:


> "for lifting, the springs are contained in the top of the cylinder head,"
> 
> ok, so the valve stems are positively pinned to the rockers. I missed that detail.


Hi,
The stems are not connected to the rockers, the valve arrangement is pretty much like a combustion engine setup, where the valves are situated in the cylinder head, and the compression spring keeps the valve tight in the valve seat, and the rocker arm pushes down on the valve, but its the spring that keeps the valve seated.
I used the same setup for both valves on my engine.


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## Longboy (Nov 22, 2018)

hobby said:


> As you can see there is a lot of things that you need to figure out on your own, that
> I just don't have any dimensions or design steps to show, it all has to be built by
> your own instincts of problem solving in mechanical design.


Thats how I do modeling too. No step by step plans to follow but making generic engine parts and fitting into a block or frame up as a base. Has worked well in I/C and Stirling for me!


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