# Vacuum engine



## oneIwilly (Jun 12, 2014)

I have been working on this engine at school. My teacher said " it would be fun". He has never made one, just found a print and said " here make this. In the print it says,at the crank shaft that it should have ball bearings. That's all it says. I tried to make it work as pictured, and it's really smooth, but won't run. I looked up some trouble shooting things for the project. That says that I should be able to spin the crank, once, hard and have the flywheel spin for two minutes. This seems crazy. Can anyone help?http://i1068.photobucket.com/albums...B-00B3-4E78-AEC7-3D5F97B75511_zpsuqykbaaz.jpg


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## Terrywerm (Jun 12, 2014)

I assume that this is a 'flame eater' style of engine, correct?  Your photo does not show a burner of any sort, but your description of it as a vacuum engine tells me that it is most likely a flame eater.  Flame eaters are notorious for being very fussy and can be difficult to get to run properly. Timing of the slide valve is very important as is burner/flame placement.

As for the ball bearing on the crankshaft, very small ball bearings are available these days (isn't technology great?) and would make your crank turn very freely, but only with the connecting rod removed so that the crank was the only thing turning when you spin it over. As for the comment about it spinning for two minutes, I have my doubts.

One last thing: Can you post a copy of the plans? If they are not copyrighted you could post them they could be shared with some of the other guys here. Maybe someone here has built that same engine and knows exactly what you need.


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## oneIwilly (Jun 13, 2014)

Yes I have a set of plans that is not copywrited. I will try to post it here. Yes it is a flame eater. I have adjusted the valve timing to every position possible. I have even made several valve rods of different lengths to get different timing. The plans that I have are very vague in this area. I got some abec 5 frictionless bearings today, and made a new crank shaft to fit them. Tomorrow I'll get the bearing supports made to hold them. Here is another pic with the intake port.http://i1068.photobucket.com/albums...5-F632-496A-AC98-497349B91366_zpsik5jqfix.jpg


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## Terrywerm (Jun 14, 2014)

I have not yet built a flame eater or vacuum engine, but I did do a little research on them to see if I could help you out. Vacuum engines such as this generate very little power, and most of them are capable of running themselves, and not much if anything else. With engines that generate so little power, there are two things that make all the difference: friction and leaks.  

Bearing friction: Ball bearings on the crankshaft should help quite a bit. As you indicated, your instructions call for a very free running design. To achieve that, you need to be sure that your bearings are installed in perfect alignment with each other, any misalignment will cause lots of drag.  

Piston fit (friction and leaks): Your piston must also be a close fit, but friction free, difficult but not impossible to achieve. You are looking for a piston to cylinder clearance of about .0005" which takes some patience to achieve. Once the piston fit is down to being a bit snug, but still movable, you need to lap it in to a proper fit. A good way to test for this is to set the cylinder vertically, then drop the piston into the bore. The piston should slowly drop all the way in on its own. If it stops, it is too tight. If it drops in quickly, it is too loose.

Valve fit (leaks): Make sure that you lap the valve to the cylinder as this needs to seal completely. If it leaks at all, even the tiniest amount, your engine will not run. Judging from the machining marks at the valve hole, showing in the photo, the valve has not been lapped in, and it will leak.

I see that the design and shape of the connecting rod can have a great effect on your valve timing, as can the length of the valve rod. An engine like this will also only run in one direction as the timing is incorrect if you try to run it the wrong direction. Some of these engines also run better once they have fully warmed up. You might try spinning the engine with a drill while the flame is present to get it warmed up. This occurs because in some engines, especially if the piston and cylinder are made of different materials, they expand at different rates, causing the piston to tighten up a bit in the bore. If it runs for a while then stops, the piston is just a shade too tight as it starts to bind when it warms up. If you can spin it with a drill to warm it up, and it runs on its own after that, it indicates that the piston is just a hair bit too small and it leaks too much until it warms up and expands.

Another recommendation that I stumbled on is to make the piston out of graphite. It is easy to machine and can be purchased on eBay or from McMaster Carr. It is also self lubricating. 

I don't have much else, I hope these tidbits are helpful.

UPDATE:  I just stumbled on the plans you used, from Jan Ridders. I was incorrect in the way I thought this particular engine works, but I can see now where there are a number of areas where leaks can occur, and I suspect this may be where you are running into problems. I can also see where this engine will run in either direction as well.


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## oneIwilly (Jun 15, 2014)

Actually the piston and valve were a little to tight. I encountered the problem where when it heats up things bound up. I did lap them in with compound to achieve the seal you are talking about, and get rid of the bind. The way that I am going to align the bearings is with a dowl pin. Thanks for trying to help me, tomorrow is the last day of class, and I'm the last student standing.yea nobody in the class got theirs to run. Also I found the article on graphite. I wanted to use it. Problem was we only had what the school had to use, hence the titanium piston and valve. This has been very difficult


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## Terrywerm (Jun 15, 2014)

Best of luck to you, and kudos to you for not giving up!

There are a number of members here in your area. Maybe one of them would be willing to help you finish and get that engine running. Take a look on the Member Map and try sending PMs to those other members in your area. Maybe somebody can help you.


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