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Home✈️Aircraft🚁HelicopterMiniature Aircraft Whiplash & Fury 55 › XCell SE 60, convert to 90. What ratio?
07-23-2006 11:11 PM  14 years ago
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kjkelly

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Austin, TX

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XCell SE 60, convert to 90. What ratio?
Considering converting my much loved XCell SE from .60 to .90 power. What I'm unsure of is what ratio to use and ideal main blade lenth. I have an OS61SXH WC in there now with a 90 tooth main and 10 tooth pinion. It has 690mm mains and the 31.5" boom with 105mm tails.

I will put in a YS91ST4. My ratio now is obviously 9.0:1. I've seen some excellent advice on this topic from DavidH in the past, but for the Fury. It does not appear that with a 31.5" boom I will have any trouble running 700's even with 105mm tails. Is my thinking correct there?

Appreciate the feedback, thank you

Kevin Kelly
"Great ideas will always encounter violent opposition from mediocre minds"
Einstein
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07-23-2006 11:47 PM  14 years ago
Jeff H

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Cincinnati, OH

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I will put in a YS91ST4. My ratio now is obviously 9.0:1
You want the 8.45 or the 8.36. Try either a 93 or 92 tooth main gear and an 11 tooth pinion.
It does not appear that with a 31.5" boom I will have any trouble running 700's even with 105mm tails. Is my thinking correct there?
100mm tails is about the longest you can get with 700s and a 31.5" boom. Get the speed up gear if your tail doesn't hold well enough but it should be fine
I've seen some excellent advice on this topic from DavidH in the past, but for the Fury.
You are oughfully new here to remember Dave's posts, unless you have been lurking for years. Dave left several years ago.

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07-24-2006 12:14 AM  14 years ago
kjkelly

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Austin, TX

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What are you targeting for ideal engine RPM with the YS91?
...and what head speed would you recommend? BTW, I met DavidH here not too long ago responding to a post here on RunRyder . . . so he apparently lurks in both

really appreciate the help Jeff. Thanks again
"Great ideas will always encounter violent opposition from mediocre minds"
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02-10-2007 08:06 PM  14 years ago
kjkelly

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Austin, TX

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Conversion Done, WOW!
Well, I've completed the converstion and all I can say is WOW! I have not yet leaned the YS91 completely yet (still running rich through the few tanks I've run in the winter) and it's already a rocket ship.

I put in the 93 tooth main and 11 tooth pinion for an 8.45 ratio. I also kept (for the time being) the 31.5 inch boom and 690mm blades. It is becoming painfully obvious that I should in the future migrate to 700 or 710's and the 32 or 33in tail boom. In it's present configuration I cannot bog the motor and I'm pulling 13 degrees at the top/bottom, and it's not fully leaned out yet!

I did have to slot the frames in order to get the motor to line up correctly. I found out that you can no longer get the required motor mount (that would have moved the motor forward the necessary 3mm) and a conversation with Tim at MA confirmed the slotting method as best.
"Great ideas will always encounter violent opposition from mediocre minds"
Einstein
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02-13-2007 06:06 AM  14 years ago
marc8090

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Long Island, N.Y.

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When I put a 91 in my SE I first ran it on 690's with the stock boom and it was better than the 61. But, putting on the 33" boom with 710's was a HUGE improvement. Just keep an eye on the head dampers, and the lower mainshaft bearing. Those two parts wore out very quickly with the 91 installed.
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02-24-2007 05:55 AM  14 years ago
kjkelly

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Austin, TX

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Describe the improvement
How so? Is it the auto's? forward speed? I'll probable do the same the next time I break the boom I have
"Great ideas will always encounter violent opposition from mediocre minds"
Einstein
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02-24-2007 03:27 PM  14 years ago
Dr.Ben

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Richmond, VA, USA

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Be careful.

Pulling that kind up pitch indiscriminantly with the stock SE clutch will eventually pull the liner out of the bell. If you feel the bell after a flight, I suspect you'll find it's pretty hot d/t the slippage that almost invariably occurs.

When we used to run 90's in our ProII's, Gordie and I both had to use the four cycle clutch to avoid repeated liner replacement.

I'm glad you're having fun, just be advised that the load on that clutch is far greater than what it was with the 60 sized engine. It is for this reason that MA had to released the H/D clutch for the Fury/Stratus/Tempest.

Ben Minor
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02-25-2007 04:59 AM  14 years ago
kjkelly

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Austin, TX

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What would you recommend?
Thanks Dr. Ben. I'm grateful that you chose to chime in on my thread. Can you recommend a solution? Can I still buy the 4 cycle clutch? ...or can the new HD clutch for the Fury/Tempest/Stratus be made to work?

Again, I'm gratful for the advice and heads up
"Great ideas will always encounter violent opposition from mediocre minds"
Einstein
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02-25-2007 05:46 PM  14 years ago
Dr.Ben

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Richmond, VA, USA

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You can call the shop and see if they have any leftover 4C bells and clutches. It's a solid clutch, so you'll need to dial indicate it. You'll also be limited to no shorter ratio than 7.9 (IE no 8.45) because the bell requires a 12 t pinion. They had tried to adapt the current pinions into that bell, but the threads are different, and they will let go in flight. Ask Gordie how we know this <g>.

The Fury/Stratus/Tempesy HD clutch will not work in an SE due to its design for a clutch driver.

You honestly do not have a perfect solution for this problem. MA never made a larger clutch for the model, since it was never marketed as a 90 sized model in its production lifetime. Gordie and I shoehorned the 90's in the Pro's b/c that was the FAI model we had at the time.

You'll just have to fly the model and see how your clutch holds up. Some do a lot better than others. All will slip, but in some the liner holds on better than others. When MA found an aerospace epoxy to bond the liners, they tended to stop coming loose, so you may need to have them redo your bell when and if it fails. The best way to manage the slipping is judicious use of large amount of collective. And the clutch gap should be TIGHT- no more than 6 thou per side.

Ben Minor
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