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vmenkal(at)mac.com
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 Posted: Mon May 31, 2010 1:44 pm Post subject: Prop reversal |
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Hi Dick. I think you may have identified one potential cause with your last line regarding prop weight.
I do recall the instructors at my iRMT course cautioning against using a prop with a high moment of inertia (as opposed to weight) as causing excessive wear on the gear box and kicking the engine backwards on stop - start.
I dont have my line maintenance manuals or prop specs with me but I believe the 3 bladed warp drive is approximately 10,000 kgm2 and Rotax specifies no more than 6,000 kg.cm2 for the current 912S (could be lower for your engine - gear box combination). Please confirm these values with Rotax and Warp Drive specifications.
I think a quick search of service bulletins would give you the correct data regarding mass moment of inertia. SB-912-042 R1 and SI-11-1991 is what I find on my computer.
Cheers Vic
iRMT
Whitehorse Yukon
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lucien
Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM
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| Posted: Tue Jun 01, 2010 8:45 am Post subject: Re: Prop reversal |
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| vmenkal(at)mac.com wrote: |
I dont have my line maintenance manuals or prop specs with me but I believe the 3 bladed warp drive is approximately 10,000 kgm2 and Rotax specifies no more than 6,000 kg.cm2 for the current 912S (could be lower for your engine - gear box combination). Please confirm these values with Rotax and Warp Drive specifications.
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I too don't have the data in front of me at the moment,  , but that figure for the Warp Drive MOI has floated around for years and is way off. One of the listers here actually performed an MOI measurement on a WD 3 blade and it was well within the 6000 kg/cm2 spec - does anyone remember who that was and what the measurement actually came out to?
I still have my WD and may do the measurement myself for grins one of these days. In any case, Daryl at WD says the prop is within the MOI limits for the 912 and C boxes and he should know .
LS
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LS
Titan II SS |
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Tue Jun 01, 2010 3:06 pm Post subject: Prop reversal |
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Lucien, It was me back in the winter of 2007. I'll have to look it up, I wrote up an article for our EAA chapter newsletter. As I recall the MOI of my 66" 3 blade with straight blades and the HP-L hub was 5800 kg cm sq.
Rick Girard
On Tue, Jun 1, 2010 at 11:45 AM, lucien <lstavenhagen(at)hotmail.com (lstavenhagen(at)hotmail.com)> wrote:
[quote] --> RotaxEngines-List message posted by: "lucien" <lstavenhagen(at)hotmail.com (lstavenhagen(at)hotmail.com)>
vmenkal(at)mac.com wrote:
>
>
> I dont have my line maintenance manuals or prop specs with me but I believe the 3 bladed warp drive is approximately 10,000 kgm2 and Rotax specifies no more than 6,000 kg.cm2 for the current 912S (could be lower for your engine - gear box combination). Please confirm these values with Rotax and Warp Drive specifications.
>
>
I too don't have the data in front of me at the moment, , but that figure for the Warp Drive MOI has floated around for years and is way off. One of the listers here actually performed an MOI measurement on a WD 3 blade and it was well within the 6000 kg/cm2 spec - does anyone remember who that was and what the measurement actually came out to?
I still have my WD and may do the measurement myself for grins one of these days. In any case, Daryl at WD says the prop is within the MOI limits for the 912 and C boxes and he should know .
LS
--------
LS
Titan II SS
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