Author Topic: LMS Oscillator - Mike's First Engine  (Read 1298 times)

Offline mikehinz

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LMS Oscillator - Mike's First Engine
« on: August 16, 2018, 12:05:14 AM »
I've been a lurker on this board for some time, but did introduce myself a few months ago. For my first engine, i made an LMS single-acting oscillator from the excellent plans found on the LMS website.  I must say they were most clear and complete.  Most of construction went pretty well, but I found making the flywheel to be the most difficult operation.  I finally figured out that to turn the recessed areas you have to grind something similar to a trepanning tool to avoid the tool rubbing and therefore not cutting properly.  Also, the flywheel doesn't run as trust as I'd hope.  I THINK the main issue with that is that the plans call for the crankshaft to be threaded and screwed into the flywheel.  The threads don't seem to hold things as true as I'd hoped.  Certain in the future on other engines I'll do something differently. 

In case anyone is curious, the cylinder, base, column, and flywheel are all 6061 and the crank, piston, and crank pin are all W1 drill rod.  The piston has no sealing element and is just closely fitted to the cylinder bore. 

I've attached pictures of all the parts and a couple of assembled photos.  Also I've attached a video of the engine running on compressed air.  It runs very well at very low air pressure.  The video shows it running on about 3psi of air. 

I know this is a pretty modest first engine, but I learned a some new techniques and about to start on a 2nd engine, which I'll fully document in the 'From Plans' portion of the forum. 

In any case, here's my very modest contribution to the group.

FYI.............Mike H.


« Last Edit: February 13, 2019, 05:26:11 PM by mikehinz »
MIke
Wichita, KS, USA

Offline b.lindsey

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Re: LMS Oscillator - Mike's First Engine
« Reply #1 on: August 16, 2018, 12:35:05 AM »
Nice job and a good runner Mike. Looks better than my first attempt. Just remember experience builds on experience. It a never ending learning process for us all. What do you have planned for #2?

Bill

Offline mikehinz

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Re: LMS Oscillator - Mike's First Engine
« Reply #2 on: August 16, 2018, 12:47:29 AM »
Bill,

I'm planning to do Elmer's 36 Reversing Oscillator.  But I'm going to do it 2x size and in imperial measure.  I'll probably post the intro to the project later on this evening.  I spent a considerable amount of time redrawing the engine using Fusion 360.  I did that for 2 reasons:  1)  I want to learn Fusion 360 and 2) I wanted to make sure I didn't mistakes in scaling the engine up.  I was also able to clear up a couple of ambiguities in the original drawings also. 

I selected the number 36 as it seems to be more complex than the LMS engine, but not so complex that I can't built it at this stage.  I'm sure though that I'll run into some tricky bits before it's all done!

Thanks for taking a look at my work and for the complement! 

Mike H.
MIke
Wichita, KS, USA

Offline b.lindsey

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Re: LMS Oscillator - Mike's First Engine
« Reply #3 on: August 16, 2018, 01:02:30 AM »
Great, will look forward to your build log on it!!  :popcorn:

Bill

Offline zeeprogrammer

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Re: LMS Oscillator - Mike's First Engine
« Reply #4 on: August 16, 2018, 02:47:45 AM »
As a first engine...that's pretty awesome and I'm betting you feel pretty good about it.

I think I remade 80% of the parts of my first engine 3 times.
(I'm on my 7th engine now and still have a fairly high remake rate.  ;D )

 :ThumbsUp:

I look forward to the next build.
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Zee-Another Thread Trasher.

Offline Kim

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Re: LMS Oscillator - Mike's First Engine
« Reply #5 on: August 16, 2018, 03:13:59 AM »
That's an excellent little oscillator, Mike!  I'd be proud to have that be my first engine!
Kim

Offline Larry

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Re: LMS Oscillator - Mike's First Engine
« Reply #6 on: August 16, 2018, 04:13:01 AM »
My first several engines were oscillators - great learning experience. Great job !

Online AOG

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Re: LMS Oscillator - Mike's First Engine
« Reply #7 on: August 16, 2018, 04:48:24 AM »
It looks great. I made four versions of that engine before I felt comfortable enough to move on to another type of engine. The secret to makeing the flywheel run true is to leave it slightly oversized. Then mount it on the crank shaft and true it up on the shaft. Second best is to mount it on an arbor made from the same stock as your shaft. If you do that (and your bearings arenít a rattle fit) it will run pretty true.

Tony

Offline mikehinz

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Re: LMS Oscillator - Mike's First Engine
« Reply #8 on: August 16, 2018, 12:40:54 PM »
Tony, thanks for the tip.  I think I figured that out, but after the fact! 

There is a small issue on the way the LMS drawings show to do the flywheel <> crank joint, at least IMO.  They show a .25 shaft with a 1/4-28 thread, so all the same diameter.  I think it would be better to have a .25 recess 1/2 way thru the flywheel and then thread the remaining 1/2 at a smaller diameter, say 10-32.  The crankshaft would then register properly on the larger diameter while still being secured.  And/or make the crankshaft a bit larger so you could turn a shoulder that would mate to a flat on the crankshaft. 

In any case, the flywheel shown was my 2nd one.  The first one died tragically in a parting incident.  I've buried that one in the backyard to hide any evidence!

Mike
MIke
Wichita, KS, USA

Online AOG

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Re: LMS Oscillator - Mike's First Engine
« Reply #9 on: August 16, 2018, 03:17:14 PM »
The shoulder approach works pretty well for registering a flywheel but there is one thing to watch out for with that approach. The tool your using to turn the shaft has a radius on it. That means that you donít get a true 90 degree corner at the shoulder. That can cause the flywheel to hang up on the shoulder and not run true. The solution is to make a slight undercut at the step. That will allow the flywheel to sit flush on the shoulder.

Tony

Offline mikehinz

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Re: LMS Oscillator - Mike's First Engine
« Reply #10 on: August 16, 2018, 05:28:09 PM »
Tony, thanks for that very useful tip!  I'll certainly keep it in mind the next time I run into that particular situation.

Mike.
MIke
Wichita, KS, USA

Offline mklotz

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Re: LMS Oscillator - Mike's First Engine
« Reply #11 on: August 16, 2018, 05:51:53 PM »
When I built Elmer's 36 I made the cylinder and upright from aluminum and had some galling when I first ran it.  A thin smear of anti-sieze fixed it but I noticed you used 6061 for cylinder and upright on the LMS engine.  You might want to think about using dissimilar materials on the Elmer's model.

Elmer's 36 will garner surprise from spectators at engine shows.  Many folks are amazed to learn that a double-acting oscillator is possible and the fact that it's reversible amazes them even more.  Enjoy your build.
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Offline mikehinz

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Re: LMS Oscillator - Mike's First Engine
« Reply #12 on: August 16, 2018, 06:11:03 PM »
Marv, thanks for the tips.  I am aware of the problems of galling.  I worked for many years in the oil field in various engineering roles.  One of the major problems we had was galling of similar metals at joints, particular the various alloys of stainless and other exotics.  We'd a lot of times use combos like hardened 4140 with beryllium copper threaded rings and thrust collars and the like.  That's where I developed an everlasting love of copper and nickel particulate embedded anti-seize type greases. 

On the LMS oscillator, I built it as drawn and as basic as I could simply since I knew it would only run for short time periods and only on low-pressure air.  I also liberally lubricate it with whatever general purpose oil I have in my shop, typically left over Shell Rotella in a squirt can.  That works ok, but I realize it's not a 'scalable' solution'.

For Elmer's 36, I'm planning on the cylinder to be 6061 but I'm going to make the piston out of either Delrin or SAE 660 bronze or maybe brass, depends on what I have around.  the crosshead guide will be DOM tubing, bored to the required ID, but for the crosshead, I'm planning on make it out of SAE 660 bronze.   The crankshaft bearing will be SAE 660 inside the 6061 housing and the cylinder pivot will be also be 660 inside that bearing housing.    What do you think about a cast iron piston inside an AL cylinder?  Backwards from most engines, but shouldn't that work??

In any case I'll document what I do in the build log.

Again, thanks for the tip!  I'm sure I'll ask for help as I go along!

Mike.
MIke
Wichita, KS, USA

Offline gary.a.ayres

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Re: LMS Oscillator - Mike's First Engine
« Reply #13 on: August 16, 2018, 10:14:57 PM »
Very nice.

I haven't built an engine yet (working on a boiler first), but when I do I'll be delighted if my first one is anything like as good as this.

All the best for the Elmer 36 build.

gary

Offline derekwarner

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Re: LMS Oscillator - Mike's First Engine
« Reply #14 on: August 16, 2018, 10:50:57 PM »
Mike....I would stay clear of any material sold as Delrin for a model piston

Too many alternate blends of synthetic materials may be supplied and some have may not have an acceptable or friendly thermal expansion properties for a model steam engine piston...

As you say, a composite bronze or brass will provide known dimensional stability when exposed to our relatively low steam temperatures at say 2 to 3 Bar

Derek 
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