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Author Topic: RC tiller arms?  (Read 7525 times)

TCC

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Re: RC tiller arms?
« Reply #25 on: January 01, 2009, 11:54:26 PM »


Why are model tiller shaped this way?



Isn't it so that the arms don't go past 'the point of no return'?

Or that point where instead of the servo pulling the arms the right way, it instead pulls it the other way. [it's the same principle as the timing of a spark plug on a piston/crank... it always fires just after top dead centre, never bang on dead centre as the combustion may send the piston down and force the crabkshaft the wrong way.]

No?

[LIONs rudders are a doosy... they are right up in a tight 'cruiser' stern and they incline in towards each other so that my tiller arms, less than an inch long, have had to have their collars filed down or they'd rub against each other. It's actually 17mm from the outer tip of the arm to the centre of the rudder post and I had to make 'em myself. mecano collars with a bit to ali/tin soldered on. They sound great but if you've seen my soldering, you'll know it's 'mass' that holds the tiller firm, not the sturdyness of the joint.

The story is actually far worse than that but that's all I'm prepared to share publicly. ;-) I'll give you a clue... I only had what looks like a 1/8th drill when I made them.... and the linkage is 1/16th? rod!!! LOL When I used to go test sail it, it would sail like this: --> ~~~~

90 turns ended up being 110!!!

My disgrace is not in doing the best I could do with what I had at the time, the disgrace is how I've fixed these oversize holes. LOL

Now you know why there's a big deck hatch above the rudders. :-)
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Marks Model Bits

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Re: RC tiller arms?
« Reply #26 on: January 02, 2009, 12:42:28 AM »

Actually you are incorrect there, ignition timing is always set a few degrees BEFORE top dead centre to allow the fuel/air mixture to fully burn just after the piston goes over top dead centre thus providing maximum force as the piston starts to decend ,  the piston is forced over TDC by its own momentum and momentum from the crank and fly wheel..

Mark.
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TCC

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Re: RC tiller arms?
« Reply #27 on: January 02, 2009, 01:28:39 AM »

Actually you are incorrect there, ignition timing is always set a few degrees BEFORE top dead centre to allow the fuel/air mixture to fully burn just after the piston goes over top dead centre thus providing maximum force as the piston starts to decend ,  the piston is forced over TDC by its own momentum and momentum from the crank and fly wheel..

Mark.

That must be why I could never adjust the points on that yamaha 100 I used to have. Does it make a difference if the engines 2 stroke or 4?

TCC... whose knowledge of mechanics matches his soldering abilities. ok2
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Circlip

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Re: RC tiller arms?
« Reply #28 on: January 02, 2009, 12:31:44 PM »

By fireing before TDC you're compressing the bang so you get more power, same with a steam engine. Fire it too early and the bang is the conrod. BTW, I think in Martin's picture the arm is the wrong way round, the lead should be the same way round as the A/C piccy.

   Regards  Ian
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