View Full Version : Simple Oscillating Engine

02-23-2007, 12:28 PM
Hello all,

I promised I would get back in the workshop and it's taken ages but finally I have!

I spend a while setting the lathe and milling machine up to give acceptable results. I designed and am part way through making a Simple Oscillating engine to get me back into the swing of machining before starting any more complex projects!

Below are some screen dumps of the assembly, I used Alibra Design free edition to do the 3D model & drawings, but the main limitation of that is only being able to save assemblies with up to 12 parts. This also means I can't create a general assembly drawing. Therefore I had to do the assembly, take some screen dumps and then watch it all go down the pan! I've still got sub assemblies saved though so it doesn't take too much to resurrect it!

Also below are some photos of what I have done so far. You can see that I it looks like I am getting a strange finish on turned components, the surface of the components. The lathe I am using is very old, however, I thought I had sorted it out and got a really good finish when I first turned the components. It was when I tried to polish them with emery cloth that I seemed to ruin the surface finish somehow.

The milled upright is somewhat of an experiment for me. I have never used my vertical milling machine before, it is a home made jobby, a Dore-Westbury. It seems to give decent results. Although the surface finish isn't great, this could be down to the cutter I used or the speed. I didn't use any coolant either. I need to practice and experiment more with this. One one side I used a slot drill and the other I used a four fluted cutter which was better but still not how I would like it.

I made a bit of a hash of the flywheel. It's ended up much thinner than I intended and hence not as heavy. I found that when I'd machined it, it wasn't running true. So I decided that when it was mounted on an arbor for turning the outside diameter I would skim across the front and that induced bad chatter marks due to not being supported enough! So I had to put it back in the chuck with external jaws and thin it down futher still! It's ended up about 1/16" thinner than it should be. I am pretty gutted about that but it will still do its job!

Last night I turned the inlet nozzle. I didn't do it as I had designed, I used a bit of brass hex instead of round as I couldn't find any round. Anyway, because the wall is thin when I tried to tighten it in I just kept going without thinking and snapped it! I think I made the thread slightly too tight so will make it slightly looser next time! At least I got the snapped part out without damaging the threads in the pedestal though!

I will keep you posted on further developments. I only have the inlet nozzle, cylinder, cylinder cover, piston, piston rod and big end to make now.

The wooden base is just a temporary thing, I may make a metal one but probably not, I will probably just end up making a better wooden one!

Certain components such as nuts / spring, screws etc. are omitted on the 3D model for ease!









02-23-2007, 04:52 PM
Nice job. I am glad I am not the only one who messes up parts and has to fix his mistakes!


02-23-2007, 04:57 PM
Thanks, we'll see when it's finished if it runs how I intended!

You certainly aren't, I'd forgotten how difficult this hobby was!

I'm a long way off being able to make an i.c. engine at the moment, but hopefully I will learn a lot of lessons from this mini project and will attempt a hot air engine next!

03-02-2007, 12:34 PM
Hello, made a couple more parts for my engine last night. Done the cylinder and the inlet nozzle now.

I did the inlet to the drawings but from aluminium instead of brass this time, simply because it's what I had in the right size. I was quite pleased with how this turned out. I made the thread slightly smaller so it is a looser fit. Just need to nip it up and maybe apply some loctite or something to stop it coming out.

I was quite pleased with the cylinder also, this was done entirely in the milling machine as I haven't got a back plate sorted out for my four jaw chuck yet. It was easier in the miller anyway. It seems to have turned out ok.

All I have to do now is piston, piston rod, big end and cylinder cover. Should be finished this weekend. Then I just need to make a proper base (haven't decided whether to do a metal or wooden one yet) and give everything a polish.



03-04-2007, 05:43 AM
Well, finished the engine yesterday and I'm quite happy with it, apart from the surface finish on some of the components and the flywheel that I pretty much messed up but didn't want to make a whole new one!

I haven't tried it yet as I have no readily available source of air, will probably try it on Tuesday night at the local Model Engineering club I am a member of.

I am confident it will run though as the ports line up nicely and it seems to turn over fairly smoothly although there are a couple of slightly tight spots. It will need running in. I think it would run better if I had made the flywheel as per the drawings but it was out of true so I had to thin it down, hence reducing the mass.

Here are some photographs, I still haven't made a decent base. I cleaned the wood up a bit but it's got oily finger prints on it again now!

I will post a video up here when I get one.





03-04-2007, 08:19 AM
I counldn't wait until Tuesday, so I tried the engine with a foot pump! It definitely works, only problem is having to keep pumping!

Just turning it over that few times has loosened it up a bit too. One design floor with the engine is that when the crank is at 90 degrees, cylinder at full tilt, the inlet port becomes slightly uncovered, meaning that lots of air or steam would escape! This would obviously make the engine very inefficient and much noisier although when the engine is going there won't actually be much time for the steam / air to escape!

03-05-2007, 04:27 PM
Hello all, had my engine running properly tonight. I remembered that someone mentioned using a CO2 bottle from the mig welder. Hooked that up and it worked pretty well. I didn't have a pressure gauge on it so not sure what pressure it was running at but it didn't feel like much. I can't turn it over on lung power though!

Below is a video of it running, let me know what you think!



03-05-2007, 07:27 PM
Nothing wrong with that! Good job.

03-06-2007, 03:42 AM
Thanks Eric, I'm fairly happy with it, there's a couple of mistakes and a design floor which hopefully I'll learn lessons from but apart from that it's not too bad.

Next project is either a flame gulper or stirling engine, have the model for the hot air engine done, just need to create the drawings. The flame gulper I haven't really got a design for yet.

03-06-2007, 12:57 PM
If you are looking for plans for a flame gulper, try here
Select English at the top left hand, and look at Vlam Happers, he seems to have got everything cracked

03-07-2007, 04:15 PM
Hi, thanks for that. They look impressive, I will have a better look tomorrow to see if I can get some ideas!