Jake A
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James, Thanks for your reply. When I watched your video of the completed engine (at 25% speed), it's clear that the valve timing is all wrong. If you concentrate on any one cylinder, you can see that one valve opens each time TDC approaches, a different valve on alternate rotations. In each cylinder, the exhaust valve (i.e. the valve you choose to designate as exhaust) should open just after BDC, and close as TDC approaches. Straight after that, the inlet valve should open, and close as BDC approaches. Then a full rotation with neither valve open. This pattern should follow the firing order (1-4-2-5-3) around the cylinders. That's how a real engine works, and if you want to teach someone how they do, it's important that the model works in the same way. With the cam as supplied, this is not possible. The engineer at Teching is now back from vacation, and I'm awaiting his response. Jake.
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I bought this kit after reading a number of positive reviews such as this one. I have been interested in radial engines for many years, but one of the things I was hoping to learn from this build was how the cams work - my 3D visualization wasn't up to the task. I had got the build almost finished, when I realized that there had been no instructions on getting the valve timing right when installing the cam 'drum' - and this was clearly very important to making an educationally valid model (and not having the valves hitting the pistons at TDC). When I took the front and back crankcase covers off, I was very disappointed to see that cam lobes are equally spaced (at 90°), meaning than one or other valve would be open on each up-stroke (or each down-stroke), rather than a down-stroke with the inlet valve open, followed by compression and ignition strokes with no valves open, and then an up-stroke with the exhaust valve open. For me, this removes any educational value the completed model might have. What experiences have other builders had in this regard? Am I mistaken, or did other builders not find it a problem? I'm trying to have a WhatsApp conversation with the engineer responsible for the design at Teching, but he is on vacation at the moment.
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