V-twin air engine (modular)

by yuris May 30, 2019
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Hey mate, really cool design i'm making the twin now, i'm keen on doubling the size and can account for all the parts except the big end bearing any ideas?


cool :)
just use the same? those bearings can hanle a lot more, as can the steel rod.
the beefier crank lobes should have no problems too, just be careful with higher rpm's and more pressure.

It was more no one makes a bearing exactly double that size and if i edit your STL to fit the original it renders all funky afterwards lol. Any decent editor i could use to adjust the housing size or did you know of something that would work 12x30x10 in size? Would make a cool project cheers

**scratch that a 6201 bearing looks like the fit just can't find one on ali is all

You could always just skip the bearing, or print one in petg or something. It will work, just not forever..
If you find something else I can always draw you a new rod, but the rods are very simple, so anyone should be able to draw one :)

yeah that's always an option : ) i might make a packer for the main shaft and use the same bearing.. the rods i can find easy enough. I'll finish this v-twin then double it and let you know how it goes thanks

Hey there ! Thanks for sharing the files ! this thing looks awesome. Now its printed im just struggling to understand how the head is monted with the valves and other components

Cool :)
did you print a twin, or more cylinders? I'm just assembling the first half of the v8..

the head consists of 3 parts. a base, middle and top.
Be sure to align them correctly, the holes should be a perfect match, if not you have something wrong.
Let's start with the valves.
You need a 39,5mm pushrod and a ~12mm rod for the valve. The valve seats into a rubber ring you should insert into the valve seat. I'll post some pic which will probably explain things a lot better..

Label one side of the engine as front. The crank is designed to run counter clockwise as seen from the front. The first cam is the intake (which should push down the valve on the left) the second cam should be rotated 180 degrees and is the exhaust cam, it pushes down the right valve.
The intake cam follower is mounted on the left side and has the bearing on the right, pushrod on the right, valve on the left.
The exhaust cam follower is mounted on the right, bearing and pushrod on the left, valve on the right. If you look at the top head piece, the hole on top is the exhaust, and should be on the right, again, as seen from the front.
I mark all the head pieces as it's very confusing.

Also take care of the valves. The 4 cylinder is running (1/2 v8) but i'm having a hard time getting the valves to seal. I'm going to try a more tapered version. The v-twin is running just fine by the way.

Thanks for taking the time to reply, things are more clear now! So far Iam building the twin so i can understand all the mechanics, then ill build the V8 =)
ill keep you in touch on how it goes and send some photos when it will be working

thanks for trying :)
if you have any questions, just ask. You might have it running before me, it takes some time.
before you build the v8, i've made some minor modifications i have yet to post. for a single row it'll work just fine.

Well... looks like its going to take 7:30 hours to print just the engine block... I might not be the first, but i cant wait to test the thing! :)
Thanks for the design!

lol. i printed it at 30mm/sec, took 5 hours for the top crank case for the twin, the v8 takes 14 :S
are you printing the v8?
Be sure to get the latest files... I just uploaded the 90 and 180 degree cranks.

There are no assembly instructions yet, but if you're printing it i will make some or take pictures of the thing assembled.
Be prepared to do some sanding ;)

And you're welcome, thanks for the note :)