Dinkus - A Side-Crank Rotary Valve Engine

[Charles Lamont]

With the ends screwed onto the rods, you would be very lucky if they were the same length. Really they could do with a simple jig. Drill and ream one end of each, then locate them on a fixed pin to make the holes at other end. However it is no big deal to open the holes to give a bit of leeway. Locomotive coupling rods have to have a bit of clearance to allow for uneveness of the road. 

[PaulR]

With the ends screwed onto the rods, you would be very lucky if they were the same length. Really they could do with a simple jig. Drill and ream one end of each, then locate them on a fixed pin to make the holes at other end. However it is no big deal to open the holes to give a bit of leeway. Locomotive coupling rods have to have a bit of clearance to allow for uneveness of the road.

Thank you Charles, I appreciate that being threaded it's a bit hit and miss but they do look quite close. I'll see how it goes as is, I could always replace them with some basic strips of metal drilled/reamed as a pair to check that everything else is in order.

[Jasonb]

You could keep the same basic rod design, even one end could be screwed on and held with Loctite so it did not turn. Make the other end a push fit so it can be slid into place and again retained with Loctite as there is no thread you will not be spacing the ends to the nearest half a thread pitch.

Or you could just unscrew one end and turn down the male threaded end of the rod . make that the push fit end but use an epoxy like Araldite rather than Loctite so it fills the thread in the existing rod end.

Ideally when you assemble make a simple jig - just two pins sticking out of a piece of flat bar which will hold the two ends to a set distance while teh Loctite sets on the unthreaded end.

[PaulR]

You could keep the same basic rod design, even one end could be screwed on and held with Loctite so it did not turn. Make the other end a push fit so it can be slid into place and again retained with Loctite as there is no thread you will not be spacing the ends to the nearest half a thread pitch.

Or you could just unscrew one end and turn down the male threaded end of the rod . make that the push fit end but use an epoxy like Araldite rather than Loctite so it fills the thread in the existing rod end.

Ideally when you assemble make a simple jig - just two pins sticking out of a piece of flat bar which will hold the two ends to a set distance while teh Loctite sets on the unthreaded end.

Thanks Jason, all good ideas in case it doesn't come together 'as is'. 

[PaulR]

Still getting no joy with this one. The holes in the rods are spaced as equally as I can get them but the valve is still oscillating rather than rotating. I could try making a new pair of temporary rods from some flat bar using a jig but I can't see it being any more accurate as I'd be doing it in the drill press. Also, if the distance between the holes was identical but didn't exactly match distance between the two crank pins I might have the same problem. 

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

I'll give it another day or two before consigning it to my 'non runner' collection (that'll make two so not too bad!).

[Jasonb]

Clamp the two pices of flat bar together and drill through both then the hole ctrs can't be different.

[crueby]

Looks like you have the two rods/pins 180 degrees apart? If you make them 90 degrees apart, then they will not oscillate. Just like a two cylinder crankshaft - one is going past top/bottom center while the other is in the middle of the stroke. I'm assuming the two valve cranks are connected to a common shaft through the valve?

[PaulR]

Clamp the two pices of flat bar together and drill through both then the hole ctrs can't be different.

Yes that's the plan but I was thinking about the distance between the holes as well.

[PaulR]

Looks like you have the two rods/pins 180 degrees apart? If you make them 90 degrees apart, then they will not oscillate. Just like a two cylinder crankshaft - one is going past top/bottom center while the other is in the middle of the stroke. I'm assuming the two valve cranks are connected to a common shaft through the valve?

Yes there's a single shaft between the valve cranks and the pins are *about* 90 degrees apart. I'm not convinced the distance between the holes in the rods is correct - I need to get the crank pins on the jaw of a vice to check and at the same time measure the distance between them. The other variable is the throw of each pair of pins but they should be identical as I made the discs in pairs. Need to find a bit more 'shop time this week to try to sort it out.

[crueby]

Boy, looking at the video the pins sure look 180 out from each other, end to end on the same shaft. Hard to tell without a side/end view though! Another thing that HAS to be the same is the distance from the center of each disc out to the center of each pin, on all four pins.

[PaulR]

Boy, looking at the video the pins sure look 180 out from each other, end to end on the same shaft. Hard to tell without a side/end view though! Another thing that HAS to be the same is the distance from the center of each disc out to the center of each pin, on all four pins.

The throw looks good on all four. I was just disassembling while making the temporary side rods and the Loctite on the crankshaft decided to come apart    I'm not having much luck with this engine and my patience is wearing very thin - one more attempt before it ends up in the scrap!

[john mills]

what is the distance between the side rod hole they need to be the same as the two shafts   the crank pins at each end should be in the same position
 at each end
john

[PaulR]

Thanks John, I've made two temporary side rods from some scrap aluminium (drilled at the same time) and now that I've got the shaft back together I can turn the engine over and the valve rod is rotating properly instead of oscillating. The only problem I have now is that there's some horrible binding that I need to track down, once that's done we'll see if it will actually run.

[PaulR]

I'm afraid to say this one is getting shelved. In principle I think it should work ok but having four cranks disks held by screws was a bad design choice, trying to set them exactly in pairs with the big end in the right place and taking account of the valve timing is horrible. Not only that but I think there's too much lateral force being exerted on the piston and a slight difference in height of the centre line of the cylinder and the centre line of the crank. So that's bad workmanship as well as a bad design  Never mind, it's all grist to the mill of experience.

[Sanjay F]

Never mind, still good going - I think your record of successes vs failures stands up for itself! 

Onwards and upwards .........what's next?