Author Topic: A Robinson from rejects.  (Read 71979 times)

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #105 on: December 09, 2017, 05:02:04 PM »
I got the cylinder liner roughed out in the week and finished it off last night followed by honing and then stuck in in today with 648.

Thought I might as well do all the bits on that page of the drawing so made the chimney and cap too. Burner spigot is still overlength and under bore until I get the burner sorted.




Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #106 on: December 09, 2017, 05:28:22 PM »
Very nice work, both!

The Robinson is a fairly simple engine with few components, I'm wondering if we'll be seeing a runner before the year is out?   :)

Cheers Graham.

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #107 on: December 10, 2017, 04:56:11 PM »
I remembered that I had a spare iron piston casting that was in the box for another set of engine castings that had been through several peoples hands so someone must be missing a piston. It also happened to have "RO" cast on the outside so I thought it rather fitting that it would get used on a Robinson engine. While I was at it I also did the wrist pin and sq headed screws to retain it.



And just so Jo won't moan that I have been neglecting my other engine projects I made a start on the little between ctrs boring bar that I will need for the Otto's cylinder :)

[youtube1]https://www.youtube.com/watch?v=YwxXUqaWLlM&feature=youtu.be[/youtube1]

J

Offline Jo

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Re: A Robinson from rejects.
« Reply #108 on: December 10, 2017, 05:21:45 PM »
:headscratch: That's less than 40mm diameter why not put it through the nose of the lathe.

Looks like its quality steel by the haze coming off the tip. Have you thought about how easy it will be to machine for the tip?

Jo
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Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #109 on: December 10, 2017, 05:25:00 PM »
 :lolb:

You lucky, lucky  :censored:  " Life of Brian " quote.

That WAS a genuine Robinson piston casting, in fact the part number was RO 4 but the number fell off years ago.

Cheers Graham.

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #110 on: December 10, 2017, 05:44:49 PM »
:lolb:

You lucky, lucky  :censored:  " Life of Brian " quote.

Always seem to come up smelling of roses :LittleDevil: There was another casting in teh same box that look like it came from the same foundry as the piston, I'll take a photo and maybe you can identify that too.

Jo I can only pass 1" through my spindle, yes quality stuff with the green paint still on the end and none of that rusty brown coating as it came from a reputable steel stockists. It machines very nicely as I also used a bit for the X-types chimney top as 35mm is near to 1.375 as makes no difference and all the EN1A I have had from Ringwood Metals in the past has been easily worked. Smoke was more likely down to the crappy Bangood tip I was trying out though the finish was not too bad for the finish cut when I reduced the depth of cut


« Last Edit: December 10, 2017, 05:59:25 PM by Jasonb »

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #111 on: December 10, 2017, 06:03:32 PM »
just looked at the photos Jo posted of the castings and the other one I have is the disc of material for the gearbox but less rusty Double Lucky  :censored:

Offline RayW

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Re: A Robinson from rejects.
« Reply #112 on: December 13, 2017, 09:18:57 AM »
Still following on Jason! Got the hot tube and burner assembly finished yesterday. Have left the bore for the burner undersize for the time being until I get the burner itself, then will bore to suit.
Ray

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #113 on: December 13, 2017, 12:08:47 PM »
Good morning Ray.

She's coming along nicely!

With regard to the burner for the hot tube ignition it seems that Primus has become Sievert since I last purchased bulk orders. The 8842 is readily available at nearly £20.00 ( found on eBay) a far cry from the good old days!

The downside to this method is that it requires a high pressure gas supply wheras the engine only needs a few PSI at the inlet valve. A dual fuel line is the obvious approach but, to my mind, looks wrong.
My method was to bring a single line from an adjustable HP Propane regulator then split off just before the fuel control valve/tap.

Wade did a range of Brass compression fitting needle valves, I used the 3/16" version with the rather awful looking plastic knob removed. The beauty of this was the fact that the compression nuts and olives were at 1/8" BSP. My trick was to soft solder over the end of the Copper pipe that fed the fuel control and then with a sharp needle pierce through the solder to make a tiny hole so that a limited amount of gas was allowed to get to the control tap.

Here's some advice for all owners of " small power " LPG gas engines. The air/gas ratio is pretty narrow for the fuel wheras the old " Town gas " was far more forgiving. Having the control tap as close to the intake as possible makes getting that mix easier to achieve. If you have distance between the two the gas can build pressure between cycles and become too rich then a misfire occurs. Using this practice I always had a reliable engine start.

Cheers Graham.

Offline RayW

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Re: A Robinson from rejects.
« Reply #114 on: December 13, 2017, 08:24:08 PM »
Hi Graham,

Thanks for that advice. I know from experience both with my Otto and my Stuart half horsepower just how critical gas pressure is. Your trick with the soldered pipe end and needle piercing sounds a really neat way round the problem of the two different gas pressures that the engine needs. I have some minute drill bits which would probably serve the same purpose.
I have seen some videos of these engines with a dual fuel line set-up and it is definitely messy looking with pipes and valves everywhere. The single feed pipe will definitely look neater.

Regards

Ray
Ray

Offline RayW

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Re: A Robinson from rejects.
« Reply #115 on: December 17, 2017, 04:12:50 PM »
The liner and piston are now finished and I am really pleased with the fit. Even with no piston rings, there is quite a bit of compression if you hold the liner upright with the bottom end sealed against a flat surface and force the piston down. I have not yet fitted the liner into the cylinder casting as I want to grind out a bit of metal from inside the casting at the top as there only seems to be the thinnest of gaps, if any, for water to get round the top of the liner, and there is plenty of thickness of material there.

I also machined the main bearing caps today and fitted them to the main body casting, ready for line boring in due course.

P.S. The grooves seen at one end of the liner in the attached photos are for the Loctite adhesive with which the liner is held in place.
Ray

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #116 on: December 17, 2017, 04:18:05 PM »
I was actually wondering how much water the top of the cylinder liner is likely to see. Looks like it will just be an air pocket to me as there is no way to bleed off the trapped air when the base if filled with water.

J

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #117 on: December 18, 2017, 06:17:12 PM »
Hello All.

I'm quietly following along, been a little unwell recently and now have vertigo. Typical as the Christmas season is nearly upon us.

Regarding the air pocket, it's not too important as that's the cold end of the cylinder. However if you're worried about it my trick was to upend the engine before running, you'd hear a glug as the water displaces the trapped air.

Some lovely workmanship being presented, makes me proud to have been instrumental.

Cheers Graham.

Offline Jo

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Re: A Robinson from rejects.
« Reply #118 on: December 18, 2017, 06:27:28 PM »
I'm quietly following along, been a little unwell recently and now have vertigo. Typical as the Christmas season is nearly upon us.

I find trying to pretend I am the fairy standing on the top of the Xmas tree after the second bottle of slurp does that to me too.. now I have learnt that it is safer not to have Xmas trees in the house  ::)

Jo

P.S. Hope you feel better soon Graham. Maybe a quick fondle of a set of Sphinx castings would make you feel better, I know it would me  :naughty:
Enjoyment is more important than achievement.

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #119 on: December 18, 2017, 06:37:37 PM »


I find trying to pretend I am the fairy standing on the top of the Xmas tree after the second bottle of slurp does that to me too.. now I have learnt that it is safer not to have Xmas trees in the house  ::)

Does that mean to say you start shinning up the trees in the garden once the bottle of port is empty :LittleDevil:

 

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