An incomplete Grasshopper

[Jasonb]

The link rods are better screwed into position and then jig drill the pin holes from the ctr of the pivot rather than measuring.

[Sanjay F]

So good news on the pivot ctr section, the length is in 0.500" - 0.502" region and when tightened rotates freely.

@Jason - just to clarify, what do you mean by 'jig drill'? The brass pivot ends have both been drilled and tapped already and the A-frame swivels have been threaded (see pictures). Does this cause an issue or should I just go with the drawing measurements for now?

[Jasonb]

The problem is when the two parts hit the ends of the male threads on the link they may not line up as it would depend where the threads started radially. If you loosen them off so the clevis is lined up then the length changes.

So ideally you screw them together adjusting things so they are tight when the slot is vertical and the central pivot horizontal. You then drill the clevis hole the right distance from the middle of the pivot

[Sanjay F]

Spent the day doing reassembly and modifying the tight interfaces between parts. The engine now turns over quite smoothly by hand and after some fiddling around with the valve gland and rod, the valve it moves up & down as it should.

I didn't get as far as the link rods as I wanted to make sure the other parts of the engine are in reasonable order before making them. The beam has now been flipped over so should now accomodate a central oiler

<a href="https://www.youtube.com/watch?v=MQkOwU4SSpo" target="_blank">http://www.youtube.com/watch?v=MQkOwU4SSpo</a>

[Michael S.]

I think it looks good. Excellent movement! 👍

[Jasonb]

Thinking about those links some more there is a way you could get them the same length using the existing parts.

Drill out the threads in the ends of the forked clevises.

Turn the link rods with one end just a plain spigot to fit the drilled out clevis, thread the other end as drawing.

You can then screw the rod into the central pivot and loctite the clevis onto the plain spigot. This will allow the clevis to be rotated to the correct orientation without a threaded connection altering the ctr to ctr length.

Just check that the end of the clevis to it's pin hole are the same on both and adjust if not.

[Sanjay F]

You weren't kidding when you said this wasn't a great design! I've spent the whole morning on the 2 rods; the original measurements given on the drawing weren't even close, luckily too long than too short. I then discovered what happened to the original rods when I tried screwing the new ones into the clevises; they were clearly snapped off some time in the past 

Through trial and error, locking the brass pivot end, and as you say rotating the clevis end I've managed to get it operational; I'm very tempted to loctite the rod and clevises together now.

https://www.youtube.com/shorts/v2U8Om1OOug

Just need to try and get the engine to run and then I can pretty up the rods. Having a little trouble with the timing, the eccentric keeps coming loose on the shaft off of the valve assembly, the tiny Allen head grub can't be biting enough

[Jasonb]

Stick a big hex head or cap head in it while you get the timing set, much easier to get a grip of. Also worth putting a bit of lead or soft aluminium in thechole first so the screw bears on that rather than tearing up the shaft.

When it come sto timing forget what is usuallly said about the eccentric leading the crank by 90deg plus another 30 or so. The action of the bell  crank in the linkages reverses that.

[Sanjay F]

I got everything I could think of looking right, port openings equal either side, loosened the valve nut in the valve, got the timing worked out, no resistance anyway and guess what .......................dead as a Dodo. 2hrs later and having played about some more, still nothing until the airline popped off and nearly hit me in the face ....... again!

The air wasn't even getting into the cylinder so I started having a poke around and couldn't believe what came out.......black sand, the sand you get with new castings, both ports were blocked solid with it (see picture). This was definitely sand not the oily gunky residue you get with old engines (I know that too well). It took ages to get it out I had to clean everything as it was everywhere. I'm so confused how can both ports still be full of the original casting sand?

Anyway, here she is running, still needs the the link arms shaping and an oiler for the beam; I must admit its very hypnotic to watch and I've been doing that for quite a while!! 

<a href="https://www.youtube.com/watch?v=0-2rvdDk5v4" target="_blank">http://www.youtube.com/watch?v=0-2rvdDk5v4</a>

[Jasonb]

Quite common and I often mention it to people building from castings with cored passages. The core sand has stronger binding agents added so does not come out easily and not being seen has to be dug out. Falls out easier if it has not been soaked in oil and rust remover

[Michael S.]

Sand mixed with oil! So you can use it for sealing too...😆

Glad the engine's running.

Michael

[vtsteam]

So Sanjay, do you think the engine had been run before? 

[Sanjay F]

That's what crossed my mind too, I honestly don't know; it came in an odd condition with most of it machined and the rods missing having snapped off in the clevises. Maybe someone put it together and never got round to finishing it or running it, hence the ports still being full of sand?

Finished by fitting a little oiler to the beam and tapered the rods. The taper turning attachment and turning between centres didn't work, luckily I used a bit scrap to test it. Finally just went with the cross slide angled over a few degress and did it by eye.

Once Santa has been and I've stuffed my face I'll start painting and a maybe a new project (I can't be sitting around watching paint dry after all)

[crueby]

Running great!!  Good find on the sand, not something you'd expect!

[Jasonb]

The sand can help with running in as it helps get rid of any tight spots

I suspect the previous builder got it all made and then threw it across the workshop in frustration of not being able to get it running due to the blocked ports and that broke the links as it hit the workshop wall