Running in a steam engine

[smfr]

I've come to the point in my first "real" from-castings steam engine build that I can turn over the crankshaft/conrod/crosshead assembly, but all the parts are still fairly tight. I can turn it over by hand with the flywheel attached, but not just with fingers on the crankshaft. You can see a video at the bottom of this post: http://www.homemodelenginemachinist.com/index.php?topic=17746.msg199110#msg199110.

So I'm wondering how folks go about running in a newly built engine. More specifically, I'm wondering:

* Whether I should consider running it in before it's fully assembled, or whether it's OK to run in the parts I have so far.
* What kind of lubrication to use. Should I consider any kind of grinding compound on stiff parts?
* How long to expect to have to run it in before things turn over easily by hand

Thanks!
Simon

 

[lordedmond]

If you are running on steam then you must use steam oil for the cylinder/s , use any single weight oil for the rest not to thick

on air use the same single weight oil for the cylinder/s

Stuart

 

[Florian]

* Whether I should consider running it in before it's fully assembled, or whether it's OK to run in the parts I have so far.

Hey Simon
If you are going to finish-machine the piston on the piston rod, this should work so far.

* What kind of lubrication to use. Should I consider any kind of grinding compound on stiff parts?

I would use some petroleum because it is very thin and lubricates not so good (that finally means breaking takes less time)

When the machine is running, you should frequently (every 15 minutes or so) put some new oil on it to be shure there is always enough lubricant.

* How long to expect to have to run it in before things turn over easily by hand

Well, this can depend very much on how it has been built and what you are using as a running in lubricant.
But it can take several hours !

I would check every half hour (just loosen the connection from the chuck to the crankshaft and turn it by hand)
and repeat until it is running as easy as you want it to.


Finally, I would not use any grinding compoud as it is difficult to get it off once applied! (The grains will stick to the softer material and not come off easily! )


By the way; For the connection of the conrod with the lathe chuck, I would use a piece of garden hose as it will compensate any offset between chuck and crankshaft.

Regards
Florian

 

[steamer]

I agee with Florian.

It'll break in on its own accord with a lubricant...no compound!

You can "motor" it as is without fear ....just keep it lubricated

A straight 20 or 30 weight bearing oil is fine

If you have a spindle oil for use on your lathe, that will do fine for motoring on the lathe.

I can recommend "Blue Velvet" brand "PB" for bearings while under steam....though it hardly justifies buying a gallon...


Dave

 

[Blogwitch]

Simon,

Be very careful if you are going to run it in by turning the crank. That is the total opposite to how an engine runs and can be disastrous if done too much.

I have a V4 oscillator steam engine knocking about somewhere that someone built and tried to run in by turning the shaft with an electric drill. After only ten minutes, the whole engine was ready for the bin, basically none of the moving parts were any good any more. All bearing and pivot points were worn oval.

The best way is to put a bit off air into it and just let it run in under it's own steam.


John

 

[steamboatmodel]

John has it right, also if running it on air use air tool lubricant on it.
Regards,
Gerald.

 

[Florian]

Hey Bogs

Dont' you think the problem with the electric dill was not the direction of the load but rather the high rpm compared to what a team engine does when under steam...?

And if the bearigns and pivots get damaged by running it by the crankshaft, then the material used is not very suitable for that application! Or that guy used some grinding compound which makes the bearings and pivots to wear very quickly!

Well, for me it does just not make any sense that the bearings should wear that fast if the the moving parts are under no load except their own weight and friction; assuming that they are being broken in with aproppriate rpm.
I mean, the bearing loads will just be into another direction and also the loads are more even because of the constant rpm of the crankshaft. (driven with the cylinder, the loads will vary as the cylinder produces a force up or down....)



But the point with running it with compressed air is of course right; I also do it that way as soon as the parts rotate free enough.


Cheers Florian

 

[Ogaryd]

Hi Simon,

I've been watching your progress on this engine and it looks very nice to me. I would recheck all friction surfaces
and find the stiff parts. When I do final assembly I carefully spin crankshaft after each new part is installed. That
way I can usually find the problem area. Personlly I wouldn't use the lathe or drill motor. I'm with Bog's, run it on air.

Garys

 

[Captain Jerry]

Simon,

If you had just rebuilt your 16 cylinder Ferrari and it would not spin freely with the heads off, would you get an 8ft cheater bar and try to get it to move? I don't think so Tim.

Same thing. If it is tight, you have to find out why.

Jerry

 

[steamer]

I agee with Florian.

It'll break in on its own accord with a lubricant...no compound!

You can "motor" it as is without fear ....just keep it lubricated

A straight 20 or 30 weight bearing oil is fine

If you have a spindle oil for use on your lathe, that will do fine for motoring on the lathe.

I can recommend "Blue Velvet" brand "PB" for bearings while under steam....though it hardly justifies buying a gallon...


Dave

My comments come from Mr Smiths book "How to build the 10V".

Dave

 

[steamer]

Oh and yes...it is assumed that it's turning on it's own accord without undue friction...some judgement is required.

If it's bound up don't just chuck it up and start the lathe!

Dave

 

[Runner]

Well how lucky am I not to get egg on my face? I was considering placing here my experience in freeing up a twin cylinder vertical steam engine that I am constructing. Well forgetting the " ........ angels fear to tread" here goes.

It is at the stage Simon is at except that it includes Stephenson's reverse gear so the 4 eccentrics and straps are in place. The size of the engine is comparable. I am able to easily turn the crankshaft by hand and with the flywheel fitted can spin with a flip of the finger 1 revolution. I did this by stages crankshaft in the bearings only using plenty of light machine oil run with an electric drill. One bearing was warm so I applied fine grinding compound.(my view is if there's tightness some small amount of metal needs to be removed, fine grinding compound gets you there quicker). Next was pushing the conrod and crosshead to and fro into the tube by hand, it should drop under its own weight. This I found was a big area for creating friction so the fine grinding compound again did the trick. And so on. Bigend bearing shouldn't be a problem.

I don't think my engine so far is ready for the bin, but registering the comments that grinding compound is difficult to remove maybe it will eventually.

Brian

 

[Blogwitch]

I knew I had a couple of piccies of the engine I was on about, a Peter Arnot V4.

It looks a real mess, but this was taken after sitting in a junk box for a few years. It's still there as far as I know.

And this was how things ended up all over it, worn out in about ten minutes.
BTW, it was by using a battery electric drill, not a mains one, so not as fast as first thought by some people.

The reason for all this damage?

One of the feed pipes from the control valve was almost blocked by silver solder, causing a back pressure whenever it was turned over, beating and wearing things into a new shape. If it was fed by air, it would have become apparent that there was a problem.

Hundreds of man hours down the drain.

John

 

[Maryak]

If your steam engine is going to run using saturated steam, cylinder lubrication is optional and depends to a large degree where the exhaust is going. Believe it or not water is a very effective lubricant with cast iron or bronze cylinders and pistons/rings.

If your steam engine is going to run using another source such as air or superheated steam then cylinder lubrication is necessary. Some so called steam oils and all airline oils are emulsify-able and some are straight heavy mineral oil; again the choice is mostly around where the exhaust ends up, i.e. you don't want emulsify-able oils anywhere near a steam engine where the condensate is returned to the boiler. They also don't work all that well with displacement lubricators.

Probably IMHO, as my old mentor was want to say, you can probably pee in it and it will run for years. We are talking 12" : 1ft here so a model is hardly likely to wear out or fail when one thinks how few hours most of them actually run.

For all the external parts SAE 30 straight oil will do the trick.

Bedding in is a matter of personal preference the so called running in compounds are aluminium oxide suspended in a carrier oil. If you choose to use a grinding compound from toothpaste on upwards in severity then thorough cleaning of the mating parts is essential after you are satisfied with the result, or they will keep on keeping on grinding.

Just my 1 Bob's worth and worth around what you paid for it.

Best Regards
Bob

 

[Florian]

Hey John

Oh well, that with the blocked pipe is of course not good and for shure the reason for that extraordinary wear of those parts.

Furthermore, I must admit that I hadn't written anything about checking all the parts.
Of course I dont' start turning any engine (or moving parts) before I am not absolutely sure that all the friction is just because of a tight fit and still in a "normal" range.
And I would also check the function of any soldered steam ports (and pipes) after silver soldering them. This usually happens when I wash the parts after pickling. Then I always check with water to see if all the ports and tubes are free...

Regards
Florian

 

[NickG]

Hi all,

I am not trying to be confrontational here but in all honesty I've never run an engine in yet, just taken care to build it with appropriate clearances, or in some cases larger than appropriate! :big:. Seriously though, I bet many people would be surprised how forgiving steam engines are. This is why I find it strange that people go to the nth degree trying to lap bores and pistons and running in tight big ends and main bearings when it's really not necessary unless you're competing in specific power output competition or something. However, most engines are either run on air a few times and put on a shelf or run at exhibitions a couple of times a year. An engine with a bit of clearance in its joints will run more smoothly and slowly and consume less air than a tight one.

I think sometimes the drawings and articles are partially to blame. Model Engineering drawings tend to give nominal sizes rather than anything toleranced which is ok as these things aren't intended for mass production and they assume the builder will machine parts in a logical order and machine them for fit rather than an actual size. Sometimes the build instructions just assume this though, they'll just tell you the method of manufacture and neglect to mention anything about fit or clearances on certain parts.

An example would be your crank webs between the bearings and the big end between the crank webs. You need a certain amount of end float in these as if your bore isn't perfectly square to the cylinder end face, piston rod perfectly square to piston, cross-head guide perfectly square to cylinder etc. it will cause a tight spot. If however, a small amount of clearance is built in, it can allow for the build up of the other geometric tolerances.

Attached is an extract from the an old British Standard BS4500 which gives a number of different types of fit and specifies the dimensions you would require to create that fit for your particular sizes. Well worth a look if you haven't before.

In my view, if an engine doesn't turn over freely by hand (and that doesn't mean there's excessive play anywhere) it's really too tight and has the wrong fit somewhere. That's not to say that running in with grinding paste and the like doesn't work, it may do if the right precautions are taken but it would just giving it the clearances that should have been there in the first place.

Looking at a car engine for example, if the correct clearances weren't there in the first place, the chances are it would quickly overheat and probably seize or destroy itself quickly. The only thing gets 'run in' is the piston rings, everywhere else there has to be room for a film of oil between the two parts otherwise it wouldn't do it's job.

It's a similar story when loctiting something ... it's no use trying to loctite something with a tight press fit and 2 smooth surfaces, there has to be somewhere for the loctite between the two surfaces otherwise how can it do anything? Another reason that a perfect mirror finish is not desirable on cylinder bores and pistons, better to have surfaces that can retain oil.

Just my 2p worth anyway.

Nick

 

[steamer]

Nick,

There's a difference between discussion and healthy debate and personal attacks. No one is doing the latter

Discuss!.....Debate....Show respect for each other....all is good!

Dave

 

[Tin Falcon]

I've never run an engine in yet, just taken care to build it with appropriate clearances.

You are very fortunate IIRC my first couple of engines ran ok without running in by an external motor my third did .

Thanks for the clearance chart I sure it will be helpful. Not enough clearance and the engine will not run too much and it will leak air or steam.
I must also add that some of the build books i have read ,recommend running in engines with some form of electric motor.
so if yo can build an engine that need no running in fantastic. if you build an engine and there are some minor rubs that need working out I see no shame in running it in and with a motor if needed.
And yes make sure there are no real issues before trying to run in an engine.
Tin

 

[Mosey]

There's an old story about the BMW boxer twin race bike being prepared for Daytona back in the late 60's early 70's. The engine was built by a gentleman named Udo Gietl, who tells how he ran in the new engine absolutely dry of oil for a very short time to seat all of the surfaces. I believe that that bike was a big winner in it's time. Nice story anyway.

 

[Tin Falcon]

I seem to remember the original VW beetle was run in on a light oil for the first couple hundred miles then the oil was changed out for the normal weight stuff.
Tin