REFLECTOR: Prop

[michalk]

Often time helicopter variants use the same internal mass components, 
but bump up the RPM by 400 or so.  That's how it is with the Franklin. 
Redline is 3200, but the internal components are identical.  I do not 
know if they modified the oil pump, which could be important.  Also the 
TBO is lower.

Scott Derrick wrote:
> Rene,
> 
> The redline limits can be a confusing issue.  There are airframe limits 
> and there are engine limits. 
> 
> Most folks are familiar with airframe limits, thats whats in the POH and 
> on the RPM gauge in a type certified airplane. This number is derived 
> from the airframe/engine/prop combination. Some combinations have limits 
> within the overall range, usually because of a harmonic issue between 
> the engine and prop.  These limits are conservative by nature.
> 
> The engine limitations by themselves are usually wider than airframe 
> limits. They are also debatable if you talk to the racing crowd.  I've 
> been told by many that I could operate my old IO360 up to 3,000 rpm 
> because I had a wood/composite prop on it. Most Catto props are rated to 
> +3000 RPM.  I did have the engine up to 1850 a few times during testing 
> but ran it below 2750 during cruise which was the Lycoming set limitation.
> 
> Wood tends to dampen vibrations vs a metal prop which tends to enhance 
> and make a vibration worse.  Thats a general rule and not inviolate.   
> Also some engine limitations are because of the type of counter weights 
> on the crank shaft, the theory being that higher rpm will wear them out 
> faster.
> 
> Since your engine is experimental and you own the airframe you can set 
> the RPM limits.  I would contact folks who race IO540's and see what 
> they say about your particular IO540 version, the D4A5. 
> 
> Scott
> 
> 
> 
> Rene Dugas wrote:
> 
>> /Mounted and flew AeroComposite prop 2.5 hrs of 5 hr fly off this 
>> weekend.  Gained 300 fmp climb at 25 squared and 8 knts in 23/23 
>> cruise from 172 knts indicated to 180 knots IAS without the spinner 
>> on.  Workmanship is beautiful but mounting hardware for spinner is now 
>> over a week late in delivery.  It was left out of the shipping 
>> container with the spinner.   Prop was two months later than promised 
>> but it does look and work very well.  /
>>
>> /Question:  The AeroComposite has a rpm limit of 3000 and an overspeed 
>> limit of about 4000.  I was thinking of increasing my engine rpms up 
>> from the 2700 of the MT to 2800 or even 3000.  That is still very low 
>> rpms and should get better climb out on take off.  Thoughts?/
>>
>> /Rene’/
>>
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