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Author Topic: running two props off one motor ?  (Read 6718 times)

class37

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Re: running two props off one motor ?
« Reply #25 on: October 11, 2009, 12:13:12 AM »

hi all,

I'm a newbie to this, but just a thought ..

if you went to five cogs, with 1 - 2 - 4 - 5 in a row, but with 2 & 4 not touching, then fitted cog three to the motor, and positioned it above this row, and meshing with 2 & 4, you would get the two props, on cogs 1 & 5 counter rotating, and still be able to keep the motor on the centre line of the boat.

depending on how you lined up your shafts the motor could also be below the line of cogs, or in line with them.

on the plan for the psv I'm building, it shows the propshafts as parallel to the bottom of the hull, so getting the motor low enough to be in line may be a problem. the real engines obviously drive from the crankshaft at the bottom of the engine.

I assume cog 3 could be a different size to either slow down or speed up the props compared to the motor.

does this sound right, or have I made a mistake somewhere ?

having a great time reading all the posts, and learning loads !!

cheers

alan
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malcolmfrary

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Re: running two props off one motor ?
« Reply #26 on: October 11, 2009, 11:03:12 AM »

As you move out from the centre, the pairs of cogs rotate the same way, so no counter rotation.  2 and 5, and 1 and 4 will give counter rotation.  Usually this is good and noisy.
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class37

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Re: running two props off one motor ?
« Reply #27 on: October 11, 2009, 01:42:30 PM »

ho hum, back to the drawing board !
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HS93 (RIP)

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Re: running two props off one motor ?
« Reply #28 on: October 11, 2009, 02:01:01 PM »

if you fix the two pinions together or find a motor with a long output shaft this does away with having the extra idler as in bobs set up and is prob easyer if you have no facileties  as you can get different length belts and by positing the motor you should be able to get the right mesh and tension.

peter
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class37

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Re: running two props off one motor ?
« Reply #29 on: October 11, 2009, 04:40:55 PM »

OK, another question on this, if you used the gears, would you still need a uj in the system, and if so where ?

I presume that with a belt system, the belts would take care of any misalignment.

cheers

alan
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HS93 (RIP)

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Re: running two props off one motor ?
« Reply #30 on: October 11, 2009, 04:50:43 PM »

I did a couple of belt drive for one prop recently both motor facing and behind and did not use joints as thats the nice thing about doing it this way.this is a heavy duty set up so you would use lighter belts but a similar set up with a longer plate and gears on the other side of the motor.
Peter
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