Modular compressed air engine (Working)

by yuris Dec 4, 2018
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I have a question, Can you label all the parts to print the 1 cylinder b/c there is multiple things and im kinda confused just label the files or just tell me to print all of them once. Thanks!

You can of course print all :P nbiut for the single you don't need the twin rod or the 4/5 cylinder cranks. The crankcase cover is optional in any case.
A nice tip though, I think i'll try to make an exploded view so it's easier to see how it's constructed..
Thanks for the comment! If you print or make anything, please post pics and in any case i'm glad to help :)

Hi, I'm the maker of the "Working 4 Cylinder Air engine" on Thingiverse and I really like your design. I saw that you would like to make it more efficient / run on breath power. This was also a major goal for me when making my engines. I also use the lifter with an airsoft BB on an o-ring and it works really well for me. I found that the lightest spring gave me the best results as it gave the least friction between the lifter and cam, but you had a great idea by making it a roller lifter. In my experience, I have not been able to make an efficient engine using just a printed piston and cylinder because of the roughness of the printed layers and slight inaccuracy of my printer. I have a working V8 model that I will try to post to Thingiverse soon that uses a Lego chain to drive the single center cam, just like a typical pushrod V8. I recommend trying to make the piston slightly smaller or cylinder slightly larger and using thin brass tube as a cylinder sleeve to make a much better air seal. I am currently working on a 2 cylinder engine with sleeving brass for the piston and cylinder to get the tightest air seal possible. You did great work on this model and hope we can put our minds together to make truly awesome small engines!

I'll send you a private message :)

Unfortinately I didn't get to run it at lung pressure. The idea of using metal liners is great, but makes it hard for people to make the 'thing'. I must say that if the tolerances are good and you print high quality, the seals do get kind of good, especially if it's a little tight and you wear them in.For me it was about the drawing. I do have a fairly large 3 axis cnc machine, so i'm on a path to create a combustion engine. Why not make the trip there fun ;)

i have a question on the second pic there is a cap on the front of the twin engine do you have a stl for this part???sorry for my bad english

I've uploaded 'Crankcase cover' to this thing. :)
I don't have a crank that will fit though, the cover is designed to hold another bearing.

you cant easily stack them to make the in line four, if you line them up 20mm appart, they collide thru the inside of the cylinder chamber... have you noticed that?

Yes, it seems the STL files are old, let me repost the bunch.
The holes to bolt the halves together should overlap.

I've just exported the files from fusion. The offset is now 21mm instead of20. The inline 5 you see in the video is the same. I've added a picture so you can see how it's supposed to fit.
Let me know if you have any issues!

Well, yesterday i tried something with your ''old'' files, have a look at this : https://www.thingiverse.com/thing:3584391
im pretty sure that will work, but i dont know yet...

i did not have the og files, but i did what i could with 3d builder, which tends to make a lot of mistakes...

If you can look into this design, and do something similar with the real files, it would be awesome! :D

V8 air engine concept (quick remix)

heheh nice.
Let me take a look later this week. At first glance i see these pitfalls:

  • shared cam but one cylinder is running backwards (will kill the cam follower)
  • cam follower needs to be split in 2 which will make it too weak
  • you can't get the cam or the pistons in..

But, let me have a go, the 'V' configuration is something that's requested a lot..:)
I am currently designing a completely different approach that's to be cnc'd but could use this to make a real 4-stroke version.

When i printed it i was able to insert the piston and con-rod from the top (like the real deal), but the assembly is quite tricky without official instructions... yet i believe it is possible to assemble it that way.

If i found the motivation i might take my own swing at it and see what i can come up with :)

ps, is it possible to use 12x6x4 bearings for this? They are a lot easier to find!

I ran into the same problem. The plan is to make a stackable v-twin (to make a v8) I'll use the 6x12x4 bearings for this design.

could you use the same principle as the radial engine, but take 90 degree instead of 120 between cylinders? sounds simple? only problem is that the exhaust/intake are not side by side...

maybe a single center cam could be the solution with pushrods...

The radial was the first engine i designed with a pushrod cam. The modular inline is the second, sort of the same.
I'm currently designing a 90 degree v-twin which can be stacked to form a v8, v6, v4, v12, whatever ;)
The 120 degree design won't allow for a 90 degree angle since the cam follower won't fit. The v-twin design will have 2 cams per cylinder (set) so i can get 2 valves (in/out) operating. It probably will not run as smooth but i hope it looks better ;)
The next step is a separate cam running at half speed and work towards something worthy of being made out of metal.

easier? found mine on ebay somewhere. are you using fusion?

This thing sounds soo good! :D now duplicate, rotate 90 degrees and make a v8 or v10! :DDD

yeps my thoughts exactly.

hmm a vr-6 would indeed be nice, I'd need a completely new design for that..
Just get the radial 3, it sounds awesome ;)
Also keep in mind that the inline 5 needs some breaking in prior to giving it a blast. it's still plastic and you will torque the crank.

any chance of getting some assembly instructions?

sure, but it will take some time. it's actually pretty straight forward. the hardest part is to get the piston moving freely with a fairly nice fit, get the valve to seal and to tap the m2 thread.
i've also made some modifications to get the inline 5 to withstand higher pressures and be self starting.
I still have the flat twin, in can disassemble it and taken pictures if you like.

very nice job! a "v" configuration would be cool