Dinkus - A Side-Crank Rotary Valve Engine

[PaulR]

Stock of some material is getting low so I had to rummage around to find some pieces for the bearings - if only I'd designed them to be of 5/8" x 1/4" steel instead of 16mm x 5mm, life would have been a lot easier! Never mind, I found just two remnants of 5mm thick bars from a suspension file drawer which were just long enough. After a bit of sawing, I glued them together and turned two sides to get the correct dimensions. I'll glue them back together and drill the oversize holes for the shaft then separate them and bore out to fit the ball races.

Also made a little lump to lift the engine and get enough clearance for the big end.

[PaulR]

Got the pair mounted and centred in the 4 jaw and drilled a 4.5mm through hole. As the shaft is 4mm I figured just a bit extra would do as the bearing race is only 3mm deep in a 5mm thick piece of steel. Used the tool I ground yesterday to counterbore the hole. It came out pretty good but the bearing projects very slightly (about 0.25mm) - I think some backlash came into play as I was constantly winding the tool around to measure the hole. Not a major problem anyway as I've allowed 0.5mm gap between the standard and the crank disk. The sealed bearing fits just right, no free play and no force needed to get it seated; I'll probably Loctite it in place in the end. Next to remount it and do the other side.

[Sanjay F]

Looks very neat and you've made lightening speed progress! 

[Michael S.]

Good progress Paul. 👍

[PaulR]

Thanks both 

Unfortunately bearing #2 didn't go to plan, the recess came out way too big, the ball race was jiggling about all over the place :'( Never mind, I've plugged the hole so I can face it flat and try again tomorrow!

[PaulR]

Things went much better after a good nights sleep. The second bearing fits snugly, both are now held in place with Loctite and I turned down the plug on the back. Everything looks nice and square but I might use a bit of JB Weld to fill that little hole and any other tiny gaps around the plug. No idea what sort of steel this is but it's pretty soft to machine although I need to remove the silvery coating.

[PaulR]

Milled the recesses for the standards and decided to modify the base and cylinder support block so the thing has a slightly less 'wall of metal' appearance' 

[PaulR]

That's about all the parts, just need to do the valve flats. I wanted to get the crank disks as near identical as I could so I made them from a single stub of steel, making the shaft hole and the crank pin holes in the lathe then sawing in two and turning each one after fitting the grub screws (I'm developing an aversion to 2.5mm socket grubscrews, as it's hard to exert enough force to properly tighten them and the key  ends up getting worn - I've shortened the one I have on the grinder about half a dozen times today!).

Waiting for some long screws to arrive in the next few days, should then be ready to assemble properly but I get the feeling this is going to be a fiddly little thing to get running....


 

[Sanjay F]

Looking like an engine! 

[PaulR]

Filed the flats and this time remembered to score a line on the end of the shaft to indicate the orientation of the flats to help when setting the timing. Filed some chamfers on top of the standards to make them a little less brutalist and made the four pins for the side rods. Oh, also made a top quality wooden base 

Just waiting on some long screws to fasten the valve block in place (as I don't fancy turning an inch length of hex down to 3mm dia!) and then it might just be ready for a spin.

[Michael S.]

The individual parts look good  , but when will the engine run?

[PaulR]

The individual parts look good  , but when will the engine run?

Maybe that should just be 'will the engine run?'  We should find out in a few days.

[PaulR]

I've had little time to devote to this over recent days but finally got all the pieces together. However, there's quite a bit of binding and it's really difficult to turn over by hand without a flywheel! I resorted to removing one crank disk at a time and replacing it with a temporary flywheel. It's possible to turn it over when one side or the other is connected but not both  I can see this is going to take some time to sort out let alone trying to get the timing right. Ho hum.

[Jasonb]

With this design any slight difference in link rod lengths or throw of the cranks at either end will likely lock things up. As a temporary measure, you could make a new rod end for one side that has a bit of an oversize hole. Not really the way to do it but it would show if the basic design is going to be a runner.

[PaulR]

With this design any slight difference in link rod lengths or throw of the cranks at either end will likely lock things up.

Yes, I thought that might be the case which is why I made the disks in pairs although the front and back pair could be slightly different. As far as I can see the rods are pretty much equal but there's bound to be some small difference. I'll persevere for a while