Basher - A Super Simple Uniflow

[PaulR]

I've sketched out a design for a very simple horizontal uniflow engine and started cutting metal. With only about a dozen parts hopefully this one will be less likely to go wrong 

I like the sound my previous uniflow experiment makes, if this one works it could be easily doubled up to a twin version which would sound even better and might run a little more evenly.

Here it is in all its glory (except the flywheel and the bearing block on the back of the frame) along with a really exciting picture of the two parts so far 

[PaulR]

Made the little block for the bearing which will be soldered in place eventually, got the cylinder to length and made the M8 portion on the back end where the valve chamber screws on. Had to undercut the thread quite a bit to get the part to screw right the way up but it looks dandy. Didn't repeat a mistake from last year where I drilled through before trying to thread a similar part and snapped it clean off  I've now remounted the cylinder the other way around ready for making the bore. After that there will be the exhaust ports to drill and the threaded holes to screw it to the frame.

As usual, here are some photos of uninteresting blocks of metal 

[55fairlane]

Watching with great interest....can you give me some e idea of dimensions? 

[PaulR]

Watching with great interest....can you give me some e idea of dimensions?

Give me a few days and I'll tidy up and post the complete plan although you might want to wait to see if it works first  I was planning on a 10mm piston with a 12mm stroke but given its length/weight I think I'll reduce the bore to 8mm (which also suits some silver steel I can use  for the piston ). I'll probably put in two exhaust ports on each of the three exposed faces of the cylinder cuboid or if I'm feeling brave I might turn down a section so I can put in a ring of exhaust holes.

[PaulR]

Almost finished the piston this afternoon. Drilled one end for the 2mm dia activator rod/pin or prodder call it what you will which is also done but needs to be hardened then fixed in place with Loctite. Cross drilled and threaded the other end using my special widget (TM) then turned it down to make it look a bit less like a plain rod Just need to cut the slot in the end which I'll do in the vertical slide. I used some chopped up drinks can to protect it while in the lathe chuck but there are still a couple of marks which are preventing it from entering all the way into the cylinder so will need to sort that as well. Really need to sort some soft jaws...

[PaulR]

Made the inlet. Actually made it twice as the first time the through hole was off centre because I was trying to hold too little hex in the chuck to turn down the round part. For the second attempt I made the hex section much deeper - doesn't match the plan but what the... it looks ok to me. Also hardened the little rod ready to fix in place after cutting the clevis and checked that it was lifting the ball the right amount. I purposely left a little extra length in the rod so it can be shortened to improve running if necessary, it's lifting the 5.5mm ball about 2mm at present.

I'll probably do the exhaust holes and the threaded fixing holes on the cylinder next then shape the frame and make a simple flywheel. I can't solder and make the bearing yet as I'm waiting for a vermiculite pad to arrive - last time I tried soldering a piece of brass angle it became horribly distorted, partly I think because it was resting on a rough thermalite block rather than a nice flat surface. Minimal soft soldering is all that's needed this time so there shouldn't be any distortion.

[PaulR]

Drilled the six exhaust ports and holes in the frame ready for the cylinder to be mounted, here it is glued in position ready for spotting through from the back. Also made a start on sawing a 2" piece of steel for the flywheel.

[PaulR]

Got the cylinder fixed in place and deburred inside the bore after drilling the ports. Continued the tiresome task of sawing the 2" steel for the flywheel. While taking a break decided to clean up the chuck as it's been getting a little 'crunchy' with bits of swarf where it shouldn't be. Winner of that competition was this length of steel 'ribbon' wrapped around one of the key socket thingies (I don't know what they're called) - must have taken some doing to get in there!

[PaulR]

Roughed out the flywheel but was disappointed to find it a very loose fit on the 5mm shaft. I drilled 4.5mm, the 4.8 and used a 5mm reamer so no idea what went wrong there. It might be ok but I might end up plugging the centre and re-doing it - depends whether or not it has any wobble. Also drilled/filed a recess for the flywheel in the base. Here are those bits just placed together.

[PaulR]

Finished the piston and fixed the actuating rod in place with Loctite. Made most of the crank disc, just need to add a grubscrew and skim the outside. Might be a few days delay now while I wait for the post.

[PaulR]

Finished the crank disk and decided to put a sacrificial screw into the bearing block ready for soldering. Man drills hole, hardly a riveting photo (there's a pun in there)

[PaulR]

Soldered the block in place and made the hole for the crankshaft. Put it together with some temporary fasteners and gave it a spin.

At low pressure (5-10psi) it oscillates back and forth, at about 20 psi it seems to be running properly but it could still be oscillating at high speed. I'll get it going then gently put a marker pen against the flywheel and see if it describes a complete circle as I can't think of any other way to check...

It wasn't running regularly at first so I swapped out the 5.5mm ball for a 6mm and that seems to have smoothed it out a bit. There doesn't seem to be any consistency in where it comes to rest so I can't tell if it's a compression issue or something mechanical. I think I may need a little less valve lift as it's probably a bit more than the intended 2mm when assembled.

It's hard to tell in the videos but this is far and away the noisiest engine I've made so far, it makes a real racket!

<a href="https://www.youtube.com/watch?v=WsKVfVj6s9Y" target="_blank">http://www.youtube.com/watch?v=WsKVfVj6s9Y</a>

<a href="https://www.youtube.com/watch?v=vDuKcu2KzpI" target="_blank">http://www.youtube.com/watch?v=vDuKcu2KzpI</a>

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

[PaulR]

Just noticed that in all three videos it does stop at the same point ie where there would be most compression. Hopefully reducing lift and therefore amount of air in the cylinder per cycle will fix that.

[Sanjay F]

Nice one, it's running, but needs refining!

Another visual effect, it looks like there are 2 x connecting rod pins which are clapping together in unison 

[PaulR]

Nice one, it's running, but needs refining!

Another visual effect, it looks like there are 2 x connecting rod pins which are clapping together in unison 

A bit of running in and reducing the valve lift to about 1.5mm has made quite a difference. It needs about 6 or 7 psi to run but is still a bit intermittent, at 15 psi it runs like the clappers and is incredibly noisy: I can barely hear a radio station on my phone even when holding it close when it's running! That'll confuse the neighbours 

Think I'll put in an extra exhaust hole on the bottom (out of sight  ) to see if that makes a discernible difference, I guess slots might be even better....

About 7 psi:
<a href="https://www.youtube.com/watch?v=kmmYaIBLRkA" target="_blank">http://www.youtube.com/watch?v=kmmYaIBLRkA</a>

About 15psi:
<a href="https://www.youtube.com/watch?v=3L1fMsNPUM8" target="_blank">http://www.youtube.com/watch?v=3L1fMsNPUM8</a>