A Step in the Right Direction

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Hi Jim,

sailplane use the propeller only to reach high altitude then they switch of the drive. If the propeller is now ridge ,not folding the propellerdrag is very high. The folding propeller is folding the blade close to the fuselage so that the drag is very low. https://aero.shima.ch/raketenwurm/ .

Happy Amps Christian

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I guess I'm looking for a blade type for carbon fiber. I trimmed my cf mountain bike bars with a hacksaw. Didn't think anything of it. I was thinking of the table saw or the chop saw for the prop with a jig. I have an 80 tooth -10 degree hook blade on thechop saw. My neighbor thought an abrasion disk would be better. That got me thinking of a hand razor saw. Bench sander for rough balancing.

Jim's post was to start practice cutting way longer than needed and sneak up on it. Great woodworking advice too!
 
Hi Grayson,

i like you test stand also very much , as it give a real simulation of the whole setup with cuppling, flexcabeldrive and strut bearing. So you get all los producting part together and see real how it workes.

To cut the carbon propellerblade i use a dremel with a diamond cuttingwheel. This workes perfect . After cuting you can stickmthe propeller on a rod and lett it run with the rod on razorblades to fine balance the propeller with the diamond cuttingwheel just grind at the havier propellerblade.

Happy Amps Christian
 
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Hi Jim,

sailplane use the propeller only to reach high altitude then they switch of the drive. If the propeller is now ridge ,not folding the propellerdrag is very high. The folding propeller is folding the blade close to the fuselage so that the drag is very low. https://aero.shima.ch/raketenwurm/ .

Happy Amps Christian
Christian,

I would not use a fold down propeller for this purpose! One important feature of the Falcon carbon propellers is the great strength of the propellers hub at the blades root.

JA

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113 has been it so far. First runs without a prop did heat up the strut a bit more. More rpm will heat it up some more. I should have titled this Breakin Stand. It's a lined Aeromarine stuffing tube. Prather grease and something called Turbine Oil from Ace. Looks like castor. It's interesting to see how much grease comes out between the stuffing box and strut. Not tons, but more than I would have thought. Bigger prop will add more heat too. A second temp sensor would probably be a good idea. I think the radio will let you do that. Living and learning.
 
Grayson,

Mark Grim is correct about the heat generated by a 1/4" steel cable rotating in a brass housing at WOT, even when there is no thrust load in either direction! I proved this to myself by setting up typical cable drive shafts in various shaped brass housings. There was no thrust load in either direction. The power source was a 1/4 HP, 30,000 RPM jig grinder. In a boat, part of the housing is being cooled by water.

JA
 
I received my Falcon prop and it's beautiful! It also going back. The hub on that thing is large. Perfect for Jim's test stand but not for my breakin stand. I did find APC racing props. Not true carbon fiber but rated higher than glass nylon or wood. .9" hub and .4" thick fits my shaft setup perfectly. I believe that 20k rpm at 180 degrees sounds right to get a new motor seated and reliable. The last few tanks I ran were 170 to 180 degrees and no idea what the rpm were. My Hanger 9 tach didn't read the narrow blade I was running. Looking forward to trying it again!
 
Grayson,

I only use the Formeco TNC tach for measuring any width propeller blade. This tach is also preferred by many pylon racers for the final setting of the engines RPM at the start line.

Jim Allen


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TNC Tachometer
Regular price$150.00

Default Title - Sold out/Call for Availability SOLD OUT/CALL FOR AVAILABILITY

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In the mid-70's, an engineer named Tony Criscimagna invented a tachometer which still stands as one of the best in existence. Soon after, Tony started a business and sold thousands of these excellent tachometers under the trade name "TNC" (his initials).

Skyborn Electronics (Powerflite) acquired the TNC from Tony around 2003, and continued to build the original design. Faced with the obsolescence of some critical components, Skyborn started to work on updating the design, but never completed this process.

July 2005:
FROMECO Scale Avionics was presented with the welcome opportunity to acquire the TNC tachometer! We are exceptionally pleased to be able to reintroduce this outstanding product to the RC modeler community.

What we ChangedProcessing: The FROMECO TNC's "brain" has been totally revised, incorporating current microprocessor technology for 0.05% accuracy and improved functionality.

Durability: FROMECO has re-engineered the tachometer's packaging. The FROMECO TNC fully protects the sensor element, has an integrated battery compartment, and is more resistant to damage.

ON/OFF control: The FROMECO TNC uses slider switch to turn the tachometer. (Picture shows buttons, Now switches.)

High RPM hold: The revised tach displays both the current RPM and the highest RPM attained. There are 5 significant digits for each measurement, for easy reading.

Upgraded components: The new TNC uses an upgraded sensor element, easily capable of obtaining RPM measurements at 6 feet under most lighting conditions. The components have been upgraded to surface mount technology, for reduced size and better durability.

What we didn't ChangeRange: The new TNC uses the same optical front end (the part that detects the propeller blades) as the original, with only minor revision for modernization of the parts. A well-proven design!

Performance: The readings are just as solid as one could expect from a TNC, even though the processing method is different. The range is still excellent. The accuracy is still outstanding. We continually compared the revised design with about a half-dozen of the originals, to make sure the new one meets or exceeds the standard set by the original TNC tachometer.

"The Name": Thanks, Tony, for a great tachometer! Also thanks to Skyborn Electronics, for allowing us to bring this tool back to the RC community!
 
Nice that will keep the prop tip speed down. My Dad always used to tell me try to never stand in line with a propeller! If they ever do shed a blade they usually go off like a bullet in the rotational arc there spinning in. Same as be careful if you drop a carbon prop or excessively jar them (not saying you did?) But even the shock of sawing that prop on a chop saw with out bracing it near the sawing point may be just enough to have it shed a blade. your not silly! so safety first. As us men love to work on our own in the shed we have to remember that means help isn't standing next to us when the SH☆T hit's the fan. Don't ask how I know this
 
Grayson,

The safest way to use any propeller type or ducted fan type loading device is with the use of an "adequate thickness" shroud around the loading device in question. The shroud does not have to be made of metal & it does not need to be round in shape. A box shaped shroud, made of high strength multiple ply hardwood plywood or a linen based phenolic, approximately 3/4"+ thick, will provide the necessary margin of safety for the RPM of the propellers used. If a propeller type device fails, it will probably fail at the propellers hub, which means that piece not only moves outward but also forward! Building a shroud, even if it is never used, is worth the safety margin it can provide!

Jim Allen
 
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