Robinson Hot Air Engine.

[NickG]

Can't wait to see the results!

[Stilldrillin]

Well, I've finally got around to having a look at things, and making a few notes......




I've also ordered new 4 & 6BA screws.

Do I paint inside the castings? Inside engine and water jacket?

I will not use "water" in the future, only coolant, or top up antifreeze/ summer coolant.

I can make a new steel section for the broken foot. Do I silver solder it in place?

David D

[madjackghengis]

Stilldrillin', if I may humbly offer a suggestion, I would find some soft cast iron and use it to repair toes and feet, and silver solder it on, as it always looks better than steel on cast iron, and it matches the thermal expansion rate as well.  Try to ignore the drool I leave on this post, as I look at all your parts and imagine putting them together in my own shop for my own running pleasure.  You've got a real "peach" there, and it should be a real runner when you get it all done.  I'm looking forward to the finished machine, running in a video.    mad jack

[Dean W]

David, I shall jump in line behind Jack with drool apologies.  Maybe American are just a bit.. drooley.  I dunno.  Watching since the start, I'm still enjoying your restoration thread here.  Oh, and I still really like this Robinson.
Considering how much rust you found, I would paint it inside.  If you heat it without coolant, it is bound to condense some moisture
in there.  Don't you think?

Dean

[Stilldrillin]

Thanks for your replies Chaps! 


Jack,
Just remembered....... I bought 2 cast iron weights from a car boot sale some months ago, 2lb & 1kilo. Hacksaw time! 

I was unsure if cast iron could be silver soldered, by me. (Only done silver soldering once before). 


Dean,
Yes, I agree re-moisture. Common sense really...... 

The recent weather has reminded me, winter is coming, and my workshop becomes a very uncomfortable place......

I have improvement plans for this engine. Thermo syphon cooling. Ballrace bearings etc.
But, the sensible thing will be to rebuild, to get a reliable runner. Then improve as time & weather allow.

David D

[madjackghengis]

Hi David, high temp silver solder works well with cast iron, lots of flux, and cleaning with an etchant or the electrolosys with washing soda, although I prefer powdered draino to remove all traces of oil from the pores, sodium hypochloride I believe, although your vinegar seems to have done a fine job so far of cleaning it up.  Definitely paint the inside as it will improve the operation of the engine as well as reduce maintenance.  When you are up and running, and working on efficiency, try stainless steel for a displacer, you can often find cans or tubes that can be modified to fit, used fuel filters for fuel injected cars are good cans, and stainless is a bad heat conductor as you probably know.  If I didn't have so many projects already, I'd probably take a stab at mimicking your engine out of bar stock, it looks great, and does interesting things with the linkage, which always attracts the attention of bystanders.  We Americans don't always drool, sometimes it collects in our whiskers on our chin and we can wipe it off before it falls, particularly as fall approaches, and the whiskers are allowed to grow.  Thanks so much for showing a very interesting engine, an amazing engine, given it ran with everything wrong with it.  Looking forward to a video when it is up and running again. mad jack

[Stilldrillin]

Well.
Now got a little time to sort Mrs. Robinson...... 

Decided to rebuild to the "first run" stage, and get it right. Rather than try to complete in one go.....

Sorted a few problems along the way. Airway plug. Grooved piston. Added extra gasket to the base flange, for insulation.

1 piece of Esbit. Got a runner.......




After a few minutes warm up, she slowed. So, I added "water", (Bluecol top up coolant). Picked up! Ran faster! 

Until the boiling radiator noises started, along with the steam...... 

She's in disgrace, in pieces again!   

David D

[sbwhart]

Perhaps its needs a Dustin Hofman to sort her out like in the film

 

Good work Dave

Stew

[Stilldrillin]

Possibly, Stew! 

But, I certainly aint any Graduate........ 


Good work? Not sure about that, until she runs properly.

Thanks anyway! 

David D

[Stilldrillin]

I've got a bit of a conundrum...... 

Need to treat every part/ joint which might leak. Starting from here, underneath the top cover......




It might be leaking between the bronze ring and casting. Can't remove the 1/8 BSPT tube. So, can't remove the ring.

I've boiled it in washing powder to degrease, and intend to run a bead of Heldite jointing compound around inside & outside of the ring.

Anyone got a better idea?

David D

[Bluechip]

Nope, no idea, but ...

How does the 1/8" BSP tube rotate to screw into ... well, whatever it screws into ??

Dave BC

[Stilldrillin]

Nope, no idea, but ...

How does the 1/8" BSP tube rotate to screw into ... well, whatever it screws into ??

Dave BC

Dave.
There was a screwdriver slot spanning the outer end of the tube.

Only, the screw plug was jammed in so tight, it broke off!   

The only way out now, is to drill the whole tube away....... 

David D

[Bluechip]

Maybe that is the problem. I would guess that the screwed end is there to make a fluid-tight joint ??

When you first posted pics. I could not work out why the U-shaped slot was there.

Would not be too difficult to remove the tube on a lathe, strapped to the cross-slide?

Sez he, not having seen it ...  

Do you have a drawing of it? Is the tube supposed to be just a tightish fit in that cast rib?

Is it gobbed up with some sealant to stop any fluid going up between the tube and it's hole? ie Can it be driven out? A blast of heat often weakens any sealant.

EDIT

Crap, my brains stopped again .... remembered ..

Is it possible to tap the inside of the stuck tube, and draw it out with a 'studding/ washer/nut/tube' puller

Dave

As 1/8" BSP is .383" nominal, I bet a 3/8" drill will be OK. Maybe the bit of tube wall left would collapse?

Baffled .. again .. just getting over a lousy head cold ...  

Dave BC

[sbwhart]

Dave

How about putting a screwdriver slot across the bit of tube sticking out, then put a length of bar through the hole that has a cross hole in the end, then slip a bit of silver steel through the cross hole so that it engages with the slot, so it work like a backward, if you see what I mean 

Hope this helps

Stew

[shoey51]

Nice one David pity it wouldn't run for when we were in STLL
cheers Graham

[Stilldrillin]

Dave, Stew.
Thanks for the thoughts and ideas.......  

Wish I'd used your backward extractor before the slot broke up Stew!  

Anyroad. I'll post a caddycrappy sketch, when I get the chance. That might explain better than my words can

Can't strip any further, without needing to make replacement parts....... Does jointing compound around the ring make sense?

Or, Should I just bite the bullet, and rip it apart?  


Graham.
Didn't we have a great day at STL!  

She will be running for the next one! Hope you and Jilly are there to see it.....  

David D

[NickG]

David,

Do you think the leak is between base and bronze ring? It should be fairly easy to seal that with a fillet of sealer around the inside diameter, or even epoxy resin like araldite, just glue the thing in place. Maybe try PTFE tape wrapped around the tube, quite a few wraps if you can get underneath it?

Failing that, are you going to run it for prolonged periods of time? I know this isn't the point ... but you could just seal it up as best you can and leave it air cooled!

Nick

[Stilldrillin]

Nick.
This is this morning's condition.....




Sealed all round with Heldite. Curing gently on a radiator. Tomorrow, mebbe, I'll re assemble, again..... 

All I want it to do, is do what it does/ can, reliably....... Then, I'll do the mods over winter. 

I know they have trouble getting rid of the excess heat. Water jacket holds 30cc. only. A thermo syphon system seems the way to go. Also, a chimney from the top of the skirt. Mebbe ballrace crank bearings.

The possibilities are (almost) endless. Once I can get her running leak free...... 

David D

[NickG]

David,

Looks to me like that should work  - if that doesn't seal it up what will! Might be worth layering the ptfe tape over that threaded section when you build it back together? Might be worth a try.

I like the sound of your mods, do you think the quality of the castings look good? I'm considering it as it's reasonably priced from Bruce Engineering. You may have said before but what is the approx. dia. of the flywheel so I can get an idea of scale?

Cheers,

Nick

[Stilldrillin]

David,
I like the sound of your mods, do you think the quality of the castings look good? I'm considering it as it's reasonably priced from Bruce Engineering. You may have said before but what is the approx. dia. of the flywheel so I can get an idea of scale?
Cheers,
Nick

Nick.
If I had the confidence. The time. A better lathe etc, I would have a go at making one..... I could do a much better job than this one!  

Have a good look here. This is done with lots more forethought....   http://www.steves-workshop.co.uk/steammodels/robinson/robinsonindex.htm

The flywheel is 4.5" dia.

Running again, (dry), this afternoon...... 

David D

[Stilldrillin]

Well...... Am I thick, or what!? The reason for the bodge has just dawned on me.......

The builder has measured the depth of the top casting, to fit the cylinder spigot.... .. And forgotten to include the thickness of the steel cover plate! 

The spigot was then too short. Adding only a ring to make up the length puts the 1/16"BSPT thread through the joint.

I would have shortened the spigot by another 8mm or so, and grafted a piece back on, to give correct overall length. The taper thread would then have passed through a solid cylinder wall.

I think it is called hindsight....... 

Keep calm, and carry on.

David D

[madjackghengis]

Well David, it sounds like you've found the fix to make that a real runner, and you may well have gotten that engine because the previous owner didn't appreciate the performance it had, and didn't know what to do about it.  I was kind of hoping to hear you decide to pull, twist or drill out that pipe, and fix it in place as it was intended, so you can get the full pleasure out of your engine.  With the ideas of circulating coolant that you have expressed, and finding this glitch, and having a plan that will fix it, I think you'll find the engine will run much better, and far more reliably giving you time to take real pleasure in it.  I'm still pouting a bit for it being yours and not mine, but I've got enough hair on my chin by now, the drool no longer drips down noticably.  I think your running video, for the finish, will be substantially different, and more enthusiastic, now that you've got a cure for that leak.  That engine almost looks like a crowd, with all its parts moving when it's running full up, a real looker.  I would definitely paint the inside with a top quality paint, and you won't be tearing it down some time down the road because of rust and nastiness leaking out from the inside.  Fine work on chasing down the cause, and finding the missing distance. Now I'm really looking forward to a finished video mad jack

[Stilldrillin]

Thanks for your encouraging words Jack!  The fun (circus?) continues...... 

I had thought to make the most of what was provided by the builder. But, not any more!   

The lady's not well......   

[ Invalid YouTube link ]



But, after a steamy few minutes...... 


[ Invalid YouTube link ]



This was running "dry". Lasting about 15 minutes from cold, until the top end is too hot, for correct function.

Stripdown time ....... Again! 

Will try to correct the problems correctly, this time! 

David D

[Rob.Wilson]

Its a Sweet runner David 

I hope you get the leak sorted 


Rob

[NickG]

David,

It seems to run really well, if only the builder had paid as much attention to the sealing faces etc as he had to the fits of the piston it would have been great. I'm sure you will fettle it though.

 

Nick