Strictly.... “ Hot Air “

[Jasonb]

I got the burner and base for my wee Robbie finished off so thought a couple of pictures were in order, seems like blue is the popular choice for these engines. All fabricated or cut from solid except the flywheel which is off a Stuart 10 size engine.











I did try it with Mamod fuel tabs without the base and it ran OK on them going nearly the full 10min burn time before slowing as the engien got a bit hot, I was nor running any cooling water. However the style of base I made would not work with the tablets as there was not enough air and the flame soon went out.

So a change of firing method was needed, I settled on a modified camping gas stove as this draws it's air from outside or in this case up from under the raised display base and also offers more control over the flame not to mention less of a smell.





As seems to be the usual case the engine did not want to run once it was all back on the base, I eventually traces this to teh flywheel being a bit close to teh bearing and rubbing but not before I had tried it with a bit more heat than I should which resulted in a scorched base and one of the joints opening up

Anyway the base repairs can wait, here is the video. Ruler make sit look a bit shorter than it is but still only 4 1/2 " from back of cylinder to front of chimney, the consequence of a small lathe 

<a href="https://www.youtube.com/watch?v=oWf9DnTIIJI" target="_blank">http://www.youtube.com/watch?v=oWf9DnTIIJI</a>

J

[Alyn Foundry]

Hi Jason.

A very nice runner, well done!

I'm guessing that the " hot pot " is quite thin as the engine came to a halt very quickly after the flame was extinguished?

Have you thought about solid fuel? Obviously no good for indoor running but at a rally smoke issuing from the chimney would be quite eye catching.

Cheers Graham.

[Jasonb]

Thanks Graham.

I did thin the base of the pot but the engine was also starting to get a bit hot all over so expect that also contributed to it loosing speed.

Not sure if I would get a good draft for solid fuel, the Mamod tabs go out straight away as the chimney does not take the fumes out fast enough even with the firebox door open.

[Dave Otto]

Very nice Jason!
Are you going to offer plans?

Dave

[Jasonb]

Not Sure, I need to talk with Graham first as I based my design on his drawings but if I do they will be here and free.

[Alyn Foundry]

Not Sure, I need to talk with Graham first as I based my design on his drawings but if I do they will be here and free.

There's no need to ask, Jason.

The Robinson hot air engine would, in patent speak be considered " prior art " and " fair game " for copying. But thanks anyway.

Very few would know that I had to get written permission from Gardner's to be allowed to put the name on our half scale engine replica. I was also informed that if our standards dropped they reserved the right to revoke that permission at any time!

Cheers Graham.

[Jasonb]

Thanks graham, I did not want to tread on anyones toes particularly as your version of this engine is back in limited production.

I'll get the working 2D drawings tidied up and probably do a separate build thread here, as I said above drawings will be free as a way of saying thanks for the info and help through this thread.

j

[Roger B]

Looks good and runs well to me    I'm sure that plans will be appreciated 

[ShopShoe]

A very Nice Runner and Great Looking.

I like the colors you have chosen.

Thank You for posting.

--ShopShoe

[Chipmaster]

My Robinson running with a new platform casting and some pictures showing the old defective casting and one of the new platform.
<a href="https://www.youtube.com/watch?v=HJR9YdzE6RY" target="_blank">http://www.youtube.com/watch?v=HJR9YdzE6RY</a>

Now I have to decide on the colour scheme.

Andy

[Alyn Foundry]

Hi Andy.

Beautifully quiet and running slowly, excellent work!

I'm guessing you'd allready finished it before now, ready for the washed out event last weekend?

It's always hard to find a colour for an engine, Red's and Greens predominate.

Cheers Graham.

[Chipmaster]

Thanks Graham. Yes, I had machined the new platform over a week ago except for drilling and threading the holes for the cylinder and crank support studs but not in time for the Broomy Hill rally. However, I displayed and ran the engine ran all day with its old platform.
Did you find a new source for the large O ring seal between the displacer cylinder and platform? I noticed that mine had suffered slight damage inflicted by the edge of the groove it sits in so I will be looking for a spare.
Andy

[Alyn Foundry]

Hi Andy.

Despite several phone calls to my original supplier we've drawn a blank. They were made from Silicone, Orange in colour and were 4 inches ID with an approximate 1/4" thickness.

The firm are now saying that at that thickness the starting ID is 4,1/2 inches progressing upwards.

I don't know if they made me a batch specially at the time but it seems they don't have a record either. Not surprising I suppose as it was over 25 years ago!

Cheers Graham.

[Jo]

Fleabay have silicon O-rings of about 100 OD of various thicknesses:

https://www.ebay.co.uk/itm/VMQ-Silicone-O-Ring-OD-30mm-to-100mm-Select-Variations-5-7mm-Cross-Section/283144176410?hash=item41ecb5431a:m:mZacR6jypu31TFLVkTQUOGg:rk:30:pf:0

https://www.ebay.co.uk/itm/6mm-Section-Select-OD-from-30mm-to-300mm-VMQ-Silicone-O-Ring-gaskets/281766787443?hash=item419a9bf973:m:maqqO72A3H2jHWB1Kvllj8Q:rk:24:pf:0

https://www.ebay.co.uk/itm/7mm-Section-Select-ID-from-76mm-to-200mm-VMQ-Silicone-O-Ring-gaskets-DORL-A/112930746431?hash=item1a4b32703f:m:majvyf8caTGdvORQ2zbUZMw:rk:31:pf:0

Jo

[Chipmaster]

Thanks Jo, I’ll check those sources.
Have you started work on your platform casting?

Andy