Slapper

[PaulR]

After disassembling yesterday I put some primer on the cylinder assembly. Today I made a slotted screw for the con rod, as the hex head screw would foul the crosshead supports, and filed away sharp edges before reassembly. Once reassembled I found the entire mechanism had become very tight so I spent ages making tiny tweaks to this and that. After running for a while without the crosshead guides in place I found that the piston rod was  rotating slightly causing the activator to get slightly under the valve stops and stop working. So, I put the lower guides in place with but didn't fasten them down, just gave the long hex screws a turn (hence the jaunty angle of the back left one in the photo!). This made a big difference, the engine will now run happily at 15-20psi, in the video I tried turning it lower and it stopped quite abruptly.

The gland nut is barely in place and there's no stuffing in there yet so there's a bit of blow through. Once it's run in a bit more I'm sure it'll run on less pressure and I can then fit the upper crosshead guides although they won't really be serving much purpose 

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

[dudeface]

Fun 

[PaulR]

Fun 

It is now it's moving, I was having doubts earlier 

Another brief run this morning and it's starting to go much better  I'll fit the upper guides later and give it a good blast. I also need to sort out the myriad screws on the underside, some of which are working loose from vibration; I've got some low strength 'screwlock' Loctite which will do the trick.

<a href="https://www.youtube.com/watch?v=Vqp662gqTZw" target="_blank">http://www.youtube.com/watch?v=Vqp662gqTZw</a>

[Sanjay F]

I like your noise and vibration dampening material - it's actually quite effective   

[PaulR]

I like your noise and vibration dampening material - it's actually quite effective   

Added some rubber feet and with lots of fettling it's quieter and much less inclined to run off!

There were a few problems which were causing the engine to randomly stop, I think the main one was the alignment of the valve guides/stops with the valve chest and the way I chose to fix them. I enlarged the holes so they no longer act as guides to keep the rod on course but merely as stops. The length of the valve itself does a good enough job of keeping the rod straight. Fixing them with a single screw through the base isn't a great design - if they work a little loose with vibration they can rotate and cause the rod to rub. That said, now that there's no contact between them and the rod the loosening seems to have gone.

I also thinned the crank by about 0.25mm as I think it was pushing the con rod outwards slightly. I decided to do away with the top bars of the cross-head as they were serving no useful purpose and creating more friction. You might see in the video that the gland nut is jiggling about as it has no packing yet.

I also think it could have done with a bigger flywheel: if I try to run it with the lowest pressure I can, the crank alternates in the same semicircle, there's not enough momentum to get it over the hump. Even so, it runs the same in each direction on very little pressure - in this video the compressor output is reading zero throughout and I turned it down until it stalled at the end.

I think that concludes this build (other than maybe applying a bit of Loctite to stop things working loose and filing down the screws at each corner).


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

[Sanjay F]

Well done Paul, another custom designed and built project to add to your collection - looking forward to seeing what you have up your sleeve next and if its the oscillator 

[PaulR]

Well done Paul, another custom designed and built project to add to your collection - looking forward to seeing what you have up your sleeve next and if its the oscillator 

Cheers! A plan for the oscillator hasn't quite clicked yet so maybe something else in the meantime. 

[Michael S.]

Hi Paul,

the motor is an excellent performer. You've implemented your idea well.

Michael

[vtsteam]

Great Job Paul! I really like your engines a lot, start to finish. 

[PaulR]

Thanks all. This one is finished now although I never got round to sorting out the screws holding the valve stops.