My first engine, and first time working with metal

[CaptSensible]

Hello there, I recently undertook my first engine build as a way to learn how to use a mill and lathe. It was epic fun, and a huge job involving around 300 hours of my time. It was an assignment for a class on learning the mill and lathe and I wanted to learn as much as possible. So I went a little above and beyond in choosing to build a 3 cylinder radial from plans and a work log Sbwhart posted here on HMEM. Huge thanks to him for doing that. I thought that if I didn't finish at least I would learn more in trying then building a wobbler. I was, I think rightly so, intimidated by the linkages in a classic 'real' model steam engine like the marine types etc I see on here. The radial looked both complex in the operations I would have to perform on the cutting machines, and somewhat simple, if precise, in its valving system.

With out further yada yada, and to keep you interested, here are some of the pictures of my work so far.

I had to make a proof of concept model out of cast plastic, I used the base of the mold as the base for the slug to be able to mill through it completely as it was a bit short for the part.

It was great practice but the design is not suited to this material. It can be milled much smoother but it has a tendency to crack if milled or lathed to thin.

I wont even show you the pictures of the rest, acrylic cylinders that chipped milling the exterior and melted ugly bores from not running the mill slow enough and with enough lubricant/coolant on the acrylic. A big fat mess that had me worried.

I thought, later proven correct, that the metal would be much easier to work with then the plastic. So I showed up at the midterm with some crappy parts and a sad look. My teacher was understanding and knew I had put in some time so he ok'ed my skipping the plastic version and going right to the metal final project.

The crank case:

Metal is so much more fun then plastic!!! And yes that slug of aluminum is hot glued to the rotary table... ummm, yeah I don't do that anymore (and it was not my idea in the first place...). It did get hot, it did melt the glue, and it ALMOST flew off but for one little strand of glue that held it slapping against the mill end as I frantically reached for the switch. In that last picture of the crank case you can see the gouges in the square piece of aluminum its sitting on, that was the mill end banging away... So I I bought some bolts and nuts for the T-slots and luck saved me from flying shrapnel.

The crank shaft:

vid of the offset being made: http://picasaweb.google.com/kenhatch/Kens3CylinderRadial?authkey=Gv1sRgCInXw8aT_crtpgE#5551818142070777586

The cylinders were kind of tough due to my having blocks of aluminum rather then the round rods that Sbwhart used in his project. I had to deviate from his work log here but it was exciting to think up how to get them done with what I had.

I should have done the bores on the lathe, but I didn't realize I could make a round extension for the 3 jaw chuck on the Lathe until after I had drilled them out. I will do it right on the next one, which will be a 6 cylinder based on this one.

The steam chest:

Again with the hot glue. Ok I lied I guess I do do this sometimes. When its a short enough process that it wont heat the part to much, and when the part is so small the clamps will get in the way of the mill if they are directly on it.

So far so good, but this is around week 8 or 9 in the semester, I have other classes to take care of, and there are only 7 weeks left to get the engine built... I am still learning as I go but feeling much more confidant at this point. I am still thinking at this point that even if I don't finish I will learn more then if I had chosen something easier. I could not try to make an easier engine, giving up sucks worse then warm flat beer.

So at this point I have made some more parts and taken much less pictures. I started to get a very good idea of the time it takes to machine accurately and what I was coming up with as far as my time frame was cause for concern. I have no experience before this and had broken a few drill bits in parts I could not replicate in time, or money of which I had none more to spend on laundry much less scrape metal.

This is were the drill bits broke, the mill was slightly off and I was drilling through 30mm of crappy re-purposed beer cans.

I got the bits out by drilling through from the opposite side with a cheap bit that was narrower then the holes that were supposed to be there. Then pushed them out using a steal rod that fit the new hole and the mill as a press. Whew, but what could happen next? I am a total newbie and haven't a clue but if it does happen I may not get this done in time!

At this point I start checking that the mill is level every time I begin using it. I share the metal shop with the rest of the students and some are pretty rough on the equipment. We have 4 mills but more then 2 in operating condition on any given day is a miracle.

Getting close to being done, just about exactly on time to finish with maybe a day to spare.

Rough exterior is not finished, but it is functional and done enough for my teachers liking. He advised me my grade was pretty much secure and I should make sure I have my other classes taken care of. I did let some thing slide in other areas to get this done, but to me it wasn't work it was the thing I most wanted to do at any given time of the day.

Here is a video of it running, it is the worst video ever I am sorry to say. The blurry gauge, nothing to really show that its running besides the audio and the wobbles from the crankshaft not being balanced yet... I will get a better one next semester but for now the shop is closed and my studio does not have a compressor. I may try to use my espresso maker to run it, if it works I will post that.

http://picasaweb.google.com/kenhatch/LastDayOfTermUpload?authkey=Gv1sRgCKmW5PzA-dC7xgE#5551823464631459986

 

[T70MkIII]

Awesome first engine build - well done!

 

[DOC123]

Well done.

 

[gbritnell]

Excellent first build. My first engine was nowhere near this good. Keep up the good work. What do you have lined up for your next project?
gbritnell

 

[b.lindsey]

Ken, I had noted in your intro thread before I saw this one...is there a flywheel somewhere? If so I am missing it. That should smooth out some or all of your running problems. You did a fine job on this engine...I wish my Machine Shop students were as dedicated as you seem to be. Given the near miss you had with the hot glue and crankcase, I hope you learned your lesson. Good solid part clamping be it with a vise or hold down clamps is not only the safe way to do things, but will improve your accuracy. And don't think that those quick little "oh I just need to drill one hole" jobs won't come back to bite you either. Not meaning to be a wet blanket here, but believe me, as a lab instructor the LAST thing I ever want is to see one of our students hurt. Speaking as a fellow forum member, we want you around a long while, preferably with 2 eyes and 10 fingers. Your work shows a lot of promise and I congratulate you for taking on such an ambitious project.

Bill

 

[Brian Rupnow]

Excellent first engine. congratulations.---A tip---Whenever running an engine witout spoked flywheels or something that is easily seen as to be revolving, put a peice of masking tape around the end of the crankshaft with a flap of tape sticking out about 1/2".---It makes the revolving action much easier to see.---Brian

 

[CaptSensible]

;D :bow:

You guys made my day! Your all too kind.

I had an advantage over the average student, I am 39 years old and living a dream of finally going to college for something I care about after spending the last 20 years working under people far less dedicated that had "degrees". So I really get into the whole thing its like being young again in some ways, both good and bad. And that's not to say 39 isn't still pretty young, I feel I can still go out and do good in the world after I graduate.

Bill to answer your question no there is no flywheel. I know it would help but I want to tune it as well as I can before putting one on so it isn't covering up something I could possibly correct. My naive way of thinking is that its an engine, engines shouldn't need a paper weight to run continuously. But it is my first so I may have to use a fly wheel in the end.

I have some design issues that may cause problems. The orbital valve shown here, the round ported brass part inside the steam chest...

...is not glued in and is loose from messing with it. It pressed in tight at first but I had to pull it out so many times in getting everything to fit that it is now loose. I suspect this causes it to be pushed into the cover of the steam chest when compressed air is sent into the engine, and causes friction that eventually stops the motor from running. I will design a new connection that is can be disassembled but is not a screw if I can, I am thinking of making the hole pass all the way through the return crank and having the orbital valves post pass all the way through with a retaining clip to keep it in place. No screws for the motion of the valve to unwind and hopefully the orbital valve can be held in place out of contact with the ported flange or cover.

I have thought up a way to easily adjust the timing on the fly, it involves making the port flange slightly wider with teeth on one quarter of the outside rim. Then having a little adjustment screw in the side of the steam chest whose teeth turn the flange and move the ports forward and back in the timing. Then another set screw to hold the flange at the desired timing. If I have worded that poorly please understand I am new to this and eager for corrections in my understanding of the terminology.

Six cylinders and an acrylic version of the 3 cylinder will be made some time in the next year. The acrylic version is for display and I want it to run very smoothly at a very low rpm. That one I will make with extreme care as acrylic is in my noob opinion much harder to work then the beautiful soft metals.

Again thanks for the comments you guys really made me smile this morning ;D

Update:

Brian, good idea! I had thought of making a propeller but then realized without a stand it would be incredibly dangerous, and even with one because the shaft is not yet balanced it would be still very dangerous. I did not get video of my teacher and the program director running it which is a bummer as that was luckily its best run, it self started and just hummed along like it knew it was its big moment. I told the director he could go ahead and boost the psi to max, around 50psi or so for the shops air system, the engine was brilliant and I wish I could have got the rpm for that, but it also I think wore some parts and its not been as smooth. I believe its correctable and the engine has room still for improvement.

Pat J., absolutely!

And to B.Lindsey,

I am listening. I was looking at the part from about a foot and a half away when it nearly came off and it scared the crap out of me. I will make smaller clamps if I have to in the future. Absolutely no more hot glue on the mill for me except for plastic which does not get hot and offers little resistance. But even then only soft plastics.

 

[winklmj]

That is an amazingly good first engine build...puts my Elmers #25 to shame. Well done! :bow:

 

[1hand]

Very impressive! Thm:

Matt

 

[Maryak]

Very impressive! Thm:

Matt

Yes, congratulations. You're now officially hooked. :bow:

Best Regards
Bob

 

[Captain Jerry]

Ken

Very impressive first effort. I see by your notes that you are moving from builder to designer. Thats where the real fun is. Small modifications that prove your ideas work can be very satisfying.

As to the orbital valve, I don't think you need to worry about face to face contact. That contact is necessary to seal the valve so that air pressure doesn't blow by and out the exhaust. You are right that air pressure is pressing the valve body against the face and that is what provides the seal. The valve body does not need to be a tight fit on the driving pin. It should be free to float. If you haven't lapped the valve body to the valve face, you may want to do that. A light oil film, provided by an air line oiler or an occasional squirt into the intake will help with the seal and eliminate or reduce any friction.

 

[CaptSensible]

Ah, thanks for explaining that action of the valve and pin Jerry. I think I will make a disk of some type of low friction plastic to go on that face the valve rubs against. If I ever make a boiler and can use steam I will make a steal cover and polish it till it glows.

 

[Ken I]

A really impressive build for dare I say - a novice.

I'm Still building my first engine.

As an experienced machinist I'm very impressed with your difficult first choice and excellent work.

Ken

 

[steamer]

Ya doing fine Captn... ;D

Dave

 

[MachineTom]

Ken that is a great result for your efforts, A+ in my book. A flywheel is not a bandaid to hide the sins of a poor design, it is a necessary part of an engine. It is needed to carry inertia from one power cycle to the next. On your 3 cylinder the pistons are on power stroke less than the 180° from TDC to BDC, with the power strokes at 120° intervals, sounds like there could be overlap, but there is not, at tdc the steam has just begun to enter the cylinder, the angle of the connecting rod is slight, very little power is developed, as the piston moves down the steam is expanding, the connecting rod angle is increasing, power is quickly increasing, at 90° rotation from TDC, max connecting rod angle power high, steam pressure has dropped off, and now the rod angle is getting smaller, less pressure less power, near BDC the exhaust begins, and now the engine absorbs power rather than generates power, as the piston forces out the steam that still has some pressure to resist the upward movement of the piston. The flywheel absorbs the power when the engine is making max, and gives it back when ther engine is absorbing power.

The flywheels purpose is not to balance the engine, it is to even out the power cycles. It can be used to balance the engine, but its purpose will always be to control the power cycles.

 

[CaptSensible]

Interesting and awesome explanation Tom, thanks! Your description helps me understand the noise profile and how it feels to turn the crankshaft by hand. The power cycles do overlap, I will draft the ported flange and orbital valve in software to get precise numbers on the overlap as my math skills are limited. I guess I need to make a flywheel when I can get back on a Lathe next semester.

Happy holidays y'all.

 

[Lakc]

Thats just awsome work for a first engine :bow:

This is were the drill bits broke, the mill was slightly off and I was drilling through 30mm of crappy re-purposed beer cans.

I have heard, from friends that spend all day making chips, stories about a certain aluminum supplier that has become famous for "gummy suprises" that pop up in the middle of blocks of aluminum.
Not to say that is always the case, its never happened to me, (not that I could blame the stock at least) but I couldnt discount the possibility.

 

[CaptSensible]

I experienced that with the aluminum plate I bought at a scrap yard. On a band saw I was cutting off a part. At first the aluminum plate felt like the other shapes of aluminum I had been cutting, and then it suddenly offered far less resistance and 'jumped' forward about an inch and a half. Just slid through the aluminum like a hot knife through butter. Then the material was hard again and the saw cut like it had at the start. Another time a classmate with the same material curled the ends of a HSS bit after drilling 2/3 of an estimated 4 inch hole through this material. The drill just stopped cutting and spun and when we looked at the tip the cutting edges were curled up, from aluminum! wth?

 

[LatheMaster]

Subscribed *discussion*

 

[robcas631]

Outstanding Job!