Starter for radial engine (Edwards 5)

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Bentwings

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No problem. I suspected as much so thought I should mention.
Thank you both for the inputs!! I think I'll visit my hobby store to buy a good starter based on Steve's advice. I thini I'm too lazy for designing and machining a new prop hub to use Cwelkie's approach, although I'll consider it seriously for my next project

There was a starter assemble buil by a guy named Miller this was based on the hobby starter with the large aluminum cup . It had a tooth or gear belt reduction drive . I don’t know what the ratio was I’d guess at least 4:1 it GSD end plates that carried the main drive shaft with the belt drive at the front. Some aluminum plates would work fine . I’ll look around for a picture it’s been years since I’ve seen one .
 

Bentwings

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Go to tower hobbies then Sullivan starters megatron you might have to search forvthe large cone cup one . I could not find it but it’s there some place
There was a starter assemble built
by a guy named Miller this was based on the hobby starter with the large aluminum cup . It had a tooth or gear belt reduction drive . I don’t know what the ratio was I’d guess at least 4:1 it Had end plates that carried the main drive shaft with the belt drive at the front. Some aluminum plates would work fine . I’ll look around for a picture it’s been years since I’ve seen one .
 

petertha

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I think the Miller units were an add-on accessory to a typical RC starter motors, more intended for the bigger gas engines. The belt & pulley system provided more output torque at reduced rpm. The idea is sound, but probably over the top for the Edwards or similar. The big rubber cone was for big spinners.
 

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Bentwings

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thatsvthebonevibwascthinkingbof . Originallyvtheyvwerebon the yellow starters I never saw a kit . I nearly purchased one but after unlearned how easy it was to start bigger gas motors ifvyou installed the prop at the correct angles I opted out. Even the zenoah Gt80 twin started easily by hand. Forvthe radial I think the belt drive might be better , at least at first there are still large and medium cone cups available.
I think the Miller units were an add-on accessory to a typical RC starter motors, more intended for the bigger gas engines. The belt & pulley system provided more output torque at reduced rpm. The idea is sound, but probably over the top for the Edwards or similar. The big rubber cone was for big spinners.
 

peterl95124

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IMHO and limited experience...

I had the same concerns with my RR Merlin V-12 model, but when the engine was complete except for lack of starter I got impatient and decided to try hand prop'ing it anyway (did put on leather gloves thou) and to my great surprise it was easy to start by hand.

in contrast to a single cylinder engine which needs to be going at a high RPM to get started because there's not much momentum in the prop and crankshaft (no flywheel), on a multi cylinder engine there's always a cylinder that's firing, at least if there are enough cylinders. With the geared Merlin V-12 a cylinder fires every 30-degrees of prop rotation, so if you push it by hand through 1/3 of a revolution you're pushing through 4 firings, any one of which will get the engine going on its own.

I'm guessing the 5 cylinder radial is going to be maybe tricky to hand start, its not geared, so the engine only fires every 144-degrees, so you can only hand push it through a single firing at a time. (a 9 cylinder fires every 80-deg, so you'll get 2 firings per hand push which should be almost as easy as the V-12)

would like to know what your experience is if/when you try it.
 

Bentwings

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IMHO and limited experience...
A popular 400cc mojo 5 cylinder radial is pretty easygoing start by hand these can run 5000 rpm snd make well over 15 hp most run 34” three bladed props it takes half a dozen flips usually
Guys do flip them pretty hard but they are a bit higher compression
I had the same concerns with my RR Merlin V-12 model, but when the engine was complete except for lack of starter I got impatient and decided to try hand prop'ing it anyway (did put on leather gloves thou) and to my great surprise it was easy to start by hand.

in contrast to a single cylinder engine which needs to be going at a high RPM to get started because there's not much momentum in the prop and crankshaft (no flywheel), on a multi cylinder engine there's always a cylinder that's firing, at least if there are enough cylinders. With the geared Merlin V-12 a cylinder fires every 30-degrees of prop rotation, so if you push it by hand through 1/3 of a revolution you're pushing through 4 firings, any one of which will get the engine going on its own.

I'm guessing the 5 cylinder radial is going to be maybe tricky to hand start, its not geared, so the engine only fires every 144-degrees, so you can only hand push it through a single firing at a time. (a 9 cylinder fires every 80-deg, so you'll get 2 firings per hand push which should be almost as easy as the V-12)

would like to know what your experience is if/when you try it.
 

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