Blockhead

[PaulR]

My next project is underway despite having only the outline of a plan. As usual it'll be a blocky bar stock build, a variation (refinement??) of the single-acting twin cylinder finished a few days ago. This time there will be a single inlet and no external pipework to the cylinders. I'll also use a scotch yoke to save a bit of space between the cylinders.

Here's all the progress I have made this evening - facing the valve block/bearing and the arms of the frame that the cylinders will be attached to. I planned on using some thinner brass for the frame but couldn't lay my hands on any so this will have to do.

P.S. Don't bother clicking the thumbnail unless you're really bored as there is nothing worth looking at 

[Sanjay F]

Is this going to called Ian after Ian Dury and the Blockheads? I instinctively clicked on the thumbnail ......... interesting! 

Looking forward to another build and you seem to be assimilating parts from your various other builds and bringing them together into this one? 

[55fairlane]

You said "blockhead" I thought we were see an "evo motor" from Harley Davidson

[crueby]

My first thought were the heads of the old Rockem Sockem Robots...

[PaulR]

  Sorry to disappoint you fellows, it won't have anything to do with robots or motorcycles (or hitting things with rhythm sticks).

As it'll be blocky in appearance and a follow on from Baldrick, in GB English a blockhead is a stupid person (bonehead, knucklehead).

[PaulR]

Not much time to get stuck in yesterday, just sawed and turned the two parts of the frame (with blue ink) down from 5/8" to 3/8" thick. I was planning on turning a spigot on the end of each of these where they enter the bearing/valve block (the bit with '19' on it) but in the middle of the night decided it would be easier to drill a hole in each and connect with a 'dowel' then solder together. That probably doesn't make much sense (!) so here's the plan which probably doesn't make things any clearer 

[PaulR]

After a day of digging with windchill bringing the air temp down to 2-3C I could only take an hour or so in the cold workshop. Managed to get the cylinders turned down to length and the bore sorted for the crankshaft. Not very exciting again but at least the shape of the engine is appearing. It's blocky. 

[Sanjay F]

That's great, I see it now - 'I love seeing a plan come together' to quote Hannibal from the A-team 

[PaulR]

Cheers Sanjay.

This morning I drilled the long passages through the two frame pieces and the short perpendicular passages to the cylinders. The ends nearest the shaft were then opened out and matching holes drilled into the valve block to meet the shaft. I made two short dowels with an air passage, these will be soldered into the frames/valve block after I've finished drilling and plugging the other five passages through the block. Here are the parts just placed together, the dowels will disappear inside when finished.

[PaulR]

Given the state of my pillar drill it's always pretty tense when trying to align small holes but fortunately all went well this morning when I drilled the 1.5mm air passages in the bearing/valve block. Now I just need to plug most of those holes! If anyone is interested, the arrows on the right image shown the route air will take to the valve flats then in and out of the cylinders (blue and red arrows) before being expelled via a hole in the shaft (red arrow). It means I'll have just a single inlet on top (which is the left side in the photo) and no external pipework.

[Sanjay F]

Given the state of my pillar drill it's always pretty tense when trying to align small holes but fortunately all went well this morning when I drilled the 1.5mm air passages in the bearing/valve block. Now I just need to plug most of those holes! If anyone is interested, the arrows on the right image shown the route air will take to the valve flats then in and out of t :popcorn:he cylinders (blue and red arrows) before being expelled via a hole in the shaft (red arrow). It means I'll have just a single inlet on top (which is the left side in the photo) and no external pipework.

That is interesting thanks for the explaination - annotated photos are better than text for sure!   

[PaulR]

Making it up as I go along and finding myself going off piste with this one...

First photo, all the bits before soldering.

Second, after silver soldering - there was some slight misalignment so some vigorous sanding was needed to get things nicely flat and square, fortunately there are no critical dimensions involved. I decided the passages that needed plugging were too close the the edges and the passages themselves so small that there was every chance of bu**ering things up so I decided to make some 'cladding' instead  This photo also shows the upper piece with the air inlet, which passes through a clearance hole and is threaded into the top of the block.

Third photo, shows one pair of holes on the side of the block which will also be covered by a small piece of brass.

Last photo, the parts in place ready for (soft) soldering tomorrow.

[PaulR]

Soldered the bits together, looks a bit rustic and still needs some cleaning up but it seems to have sealed things without blocking any passages.

[Roger B]

Another interesting design to follow along     

[PaulR]

Cheers Roger.

I've now got the cylinders mounted, with the final bit of air passage drilled in each one. Thankfully the alignment between the two bores seems good, testing here with a long piece of silver steel.

[PaulR]

Made the end caps from brass hex - because I've got some in the right size that never seems to get used so why not - and Loctite'd in place. Also made the pistons and rods, next will be the crankshaft/valve.

[Sanjay F]

Looking good and the build is motoring along! 

[PaulR]

Filed the flats on the shaft using my cross-drilling widget so it could be flipped 180 in the vice. I thought about milling the flats but realised I don't have an end mill small enough to do the exhaust flat; doing it the manual way was probably quicker anyway. Just need to drill the longitudinal hole and that part is finished.

[PaulR]

Finished drilling the valve and made the crank disk only to find I don't have an Allen key for the 2.5mm grub screw  so will need to sort that. Next will be the crank pin which will have a little step to keep the yoke away from the disk.

[PaulR]

Chucked the grubscrew idea and turned down the head of a stock stainless screw to make a slotted one instead. Also made the crank pin, just the yoke and flywheel to go.

[PaulR]

Mostly finished the yoke but have to give the fingers a rest! Made some filing buttons to do the ends, took care to get the holes at the end of each slot in the right place then eyeballed some smaller ones in the middle (my eyeballs must be wonky  ) and did more filing. Still need to tart up the ends and do some fine adjustment to the slot but it's mostly done. Should really have made a cross hole for the piston rods to screw into before I started but should be ok to do at the end.

[Michael S.]

Hi Paul, that must have been a lot of hard work with the file. It looks great though! 👍

(My fingers always hurt a little after filing like that. Must be getting old.)

Michael

[PaulR]

Hi Paul, that must have been a lot of hard work with the file. It looks great though! 👍

Thanks Michael. I couldn't resist finishing it off this evening so the fingers are really hurting now!

[Sanjay F]

Nice finish though given your manual labour and shortened fingers - well worth it!

[PaulR]

Nice finish though given your manual labour and shortened fingers - well worth it!

Cheers 

Made a simple flywheel and put the bits together but it was impossible to turn over by hand because the hex section of the crank pin was pushing the yoke away from the frame - some slight miscalculation or error in my partial plan. I took it out and put in a 3mm screw and the engine then turned over nicely by hand so I connected up the air supply and it went pretty well, even self-started at one point, reading 0 to 5 psi. That's with one screw instead of four holding each cylinder on (so pretty leaky) and almost no lubrication 

I'll make a new pin but put the hex section on the outside and sort out some sort of supports for the whole thing. This and the previous engine seem pretty solid designs but I don't like the construction method for either so I'll maybe try a third variant and somehow drill longer passages in a thicker frame... thinking.


<a href="https://www.youtube.com/watch?v=bsSHpd7aLUs" target="_blank">http://www.youtube.com/watch?v=bsSHpd7aLUs</a>

[Sanjay F]

Another runner ....... a round applause for that man! 

Well done Paul

[Michael S.]

Congratulations, well done 👍

[Roger B]

A runner     

[PaulR]

Roughed out some supports and a little base to do some running in. Probably need to fit some rubber feet to stop it going walkies when running at speed 

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

[vtsteam]

Runs great Paul!

[Michael S.]

A good runner!

Well done! 👍

Michael

[Sanjay F]

Yep that's good'un, well done Paul 

[55fairlane]

Love it

[Zephyrin]

clever engine and original project, congratulations !