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PostPosted: Fri Mar 21, 2008 12:19 pm
by huronflyer
If I add a set of redrives to my R 185s...

will I need leading edge doublers and other modes to the wing?

PostPosted: Fri Mar 21, 2008 1:17 pm
by JPXman
the consequences of adding a redrive:

1. thrustline is lower, so the distance between where the torque from the thrustline is applied to the wing goes from ~0 (bi-props centre is right in the middle of the Dcell vertically) to a distance of about 6" from the hung redrive prop (1/2 the diameter of small pulley + 1/2 diameter of large pulley + pulley gap)

2. overall thrust increase. due to the prop turning more slowly it is more efficient and so provides more thrust at all speeds provided the 185 can still churn away at hopefully 5800rpm (normal bi-prop rpm)

To add a redrive, at a minimum I would add the D-cell skin doubler (4' section) and convert to the long bolt modification. The skin doubler will help distribute the added torque of the offset thrust centreline which acts to twist the D-cell around the nacelle attach points. The longbolt mod will help distribute the now uneven shear forces on the attach bolts. This mod incorporates plates on the top and bottom of the wing which also helps distribute the load the nacelle puts on the wing - essentially making the nacelle wider.

that's my best guess!


PostPosted: Wed Mar 26, 2008 2:08 pm
by huronflyer
Thanks Tyler,

That is important stuff.


PostPosted: Fri Apr 25, 2008 12:29 pm
by huronflyer
And anyone else...

I was talking to a former redrive user (185s) and he mentioned they were HARD
to start, which caused him to go to another option.

Chappy says his redrives on Pioneers are easier to start...

So is it a rule that redrives on bigger engines are harder to start or is this an exception with the 185 and particular redrives?

Anyone out there know more about this...

Electric start is a possibility; WGT!!! Jim found a ring gear that fit his 185s, BTW has had a dead end on a small starter that fits gears AND turns the right direction.


PS Working on getting her back in the air ASAP

PostPosted: Fri Apr 25, 2008 3:25 pm
by JPXman
one person's passing comment does not make a fact. 1000's of lazairheads, all with their own opinion's on things.

did you ask him why they are harder to start? did he remove release valve and forget to tell you? :) that would make them harder to start. does he mean the engine doesn't fire as quickly, or is harder to physically pull?

The dirt is always in the details.

Edmonton, AB

PostPosted: Sat Apr 26, 2008 10:10 am
by huronflyer
He said they were one, harder to physically pull,
could that be because of the added pulley and belt?

He also has the enclosure like you, which he says added to
the challenge before he switched to different engines.

They have at least a half-dozen Lazairs and Lazairheads in their
group, his sonflies a Lazair and is a FI - so I doubt it is the
decompression valves.

I would still like to give them a go. (Start lifting weights - laugh).

TX for feedback.


PostPosted: Sun May 18, 2008 12:20 pm
by yankeflyer
More on re-drives, adapting some of the paraplane motors coming out of Europe.

PostPosted: Sun May 18, 2008 12:22 pm
by yankeflyer
Sweet looking re-drives-