Anyone interested in makeing a 3 bladed prop ?

[asra]

At the risk of Being told I'll Kill myself ONE MORE TIME ... I thought I'ed share how I have built up a 3 bladed prop for my gyro .. if your intrested say so if not ... i won't bother ! C ya !Bob....." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[asra]

Hang it on us Bob.Aussioe Paul.www.firebirdgyros.com

[asra]

Okie Dokie Paul !here are some pics of the proccess...Note that the prop blades are for a tractor not a pusher but besides that the proccess is the same... I need to make a new set of blades for my gyro I will use better wood and make the blades thinner and then fiberglass them...I have yet to spin them up to see if they'll withstand the 6500RPM If theydo then I'll adjust the pitch to them and call it good .... but like i said I need to make another set of blades first ....the idea here is a 3 bladed adjustable pitch prop the Blade clamps are of Flooring plywood and clamp extreamily well to the blade shafts.... infact you'ed tear the blade off trying to get it to slip....the Prop Hub is missing the spacers .... their in use at the moment ! here's the pix...Image Insert: 43.44

[asra]

Bob, you are a guy of many talents!!! BUT remember flying is not one of them yet!!!I would have done the blade root a slightly different way. Now see if I can attach a pick. Then attach the alloy bits.Regards, Aussie Paul.[]Image Insert: 23.95 KBwww.firebirdgyros.com

[NiqueNaque]

Bob,Scarey...Have you load tested it with a dead weight in the hub equal to at least the weight of your gyro? There are large centrifugal forces on the blade in motion, in addition to the bending moments applied by the thrust of the blade and shock factors from the blades passing through turbulence off the gyro body, especially on a pusher. Wood is a good choice for vibration proofing but the shanks on those are a weak point. If you can put the prop up on sand bags at 2/3'ds the diameter out and drive your car over the hub without it breaking, it should be ok, but if you hear any splintering or cracking noises, I'd beef it up some.Are the shanks of the blades tapered at all? If not the plate and screw you have fastened into the end grain will stay and the rest of the blade will go walkies on you.How have you balanced it?Take care.Cheers,Nick.

[asra]

Aussie Paul ! good to see ya here again buddy ! ...who said anything about flying ? hehehehehhehehehe your right I ain't a pilot yet but I will be .as far as the blade Root goes ... You hit the Nail on the head Paul... that is what the blad root will look like when their done ... the alum cap on the end ( held in by a single screw for looks at the moment ..) will be fiberglassed in as well as multable screws to hold it on .... I realise the blade has alot of centrifical force on it guys My warp drive prop is made the same way but with carbon fiber and alum tubeing at the root ... the important thing here is the clamping action of the plywood clamps after their glassed they will be more than plunty strong to withstan the forces handed to them .... at least I think so ( grin) As with anything i make up I make it stronger than it needs to be ... then test it .... if it fails in testing then it wasn't strong enough ! hehehehehehhewhat I'll do is make up a set of PUSHER blases ,,, because for the 2nd time now i made props in the wrong direction ! the blades have the flat side to the front ...and it should be on the back .... No doubt they would still push air but not as effeciant as they could be ....I still have a long way to go on this thing ... I have to ballance the thing perfectly.... as well as get all the fiberglassing done on it ... then I'll mount it on the Rotex and set the pitch to zero degrees.... and spin it up to 6500 RPM ....and try to sustain the spin as long as I dare without hurting the engine .once thats done then I can set the max amount of pitch my Rotex can push .... and put it into use ! ....I wanted to show you guys the EARLY stages of the work, because that usually gets overlooked or lost ..... as you can see the thing is NOT that complicatedto be totally honnest I think I would change the blade clamps to solid alumimum if i were to do it over again ... infact i still might ........ the hardest part of working with the alum hub plates is cutting them out ... I don't have a ban saw ! the hardest part on makeing the blades is the hours of grinding /sanding down the wood on the airfoil shape I just did it by eyeball and got them all very close to being the same .... they should be exactly the same ... but the prop will still funtion even if their not . the Hub plates are out of 3/16" thick alum plate , the hub plates on my warpdrive prop are only 1/8" so I have beefed it up alot ...the 1- 1/2" blade shafts at the root of the blades are indeed a weak point ! infact if the props ever hit anything i ecpect them to snap off there , if they don't survive the spin-up test and explode on me then I'll have to laminate an alum tube and fiberglass/wood blade of some sort .... but thats down the road a piece !.....it should be interesting to see the results between this prop and the warp drive prop at the least ! once i am totally done and all that with the prop I will give ya all an update on what else I had to do to make it work ! take care youz guys !Bob......." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[asra]

Bob, Free advice, Dont zero pitch your prop when testing.The EGT's on your "Rotex" will go thru the roof if its not loaded down sufficiently.pitch your prop enough to get around 6500,and then stand well back.M Barker

[asra]

Ahhh thanks Murray ! i didn't know that .... I'll keep it in mind ! .... I alwayse watch the temp anyway .... ...... and beleve me I will be standing well back with my hand on the kill switch ! Thank you for the info !Bob....." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[NiqueNaque]

Murray,Good thinking, would it be a good idea to overpitch it, eg, 20 degrees to make sure it was stalled but still pulling air through for cooling?Nick.

[mrford61]

quote:Originally posted by Bob K.At the risk of Being told I'll Kill myself ONE MORE TIME.You can only kill yourself once Bob.Just out of curiosity, what is wrong with the prop you have. Is that why your gyro wont leave the ground ??

[Tim]

Standing by the kill switch probably will not help much Bob - If it throws a blade you will not be able to operate the switch until it has torn the gearbox off the engine and settled down. If then the engine is at full noise with no load then you may not be able to shut it down because they have been known to self ignite like a glow plug engine and keep running with the ignition off. Sort of like "self destruct" mode. Cheerful bugger arn't I.If you are serious about trying this prop then you could bolt it to some old heavy car style engine and put it through its paces that way. Most prop makers had failures (some times many) before they got it right.Tim McClure

[asra]

I am aware of that Tim ... if it does let go its too late .... but thats how to test it for failure spin it faster than it needs to be used at .... i don't know of any other merhod of practically testing a wood blade for failure ... other than that ... an extra car engine isn't something i have laying arround hehehehe....the prop I am useing on my gyro is a warp drive adjustsable pitch prop ... If nothing else it may inspire someone to try and build their own prop so they can get into the air if your carefull it can be done ... after all the wright brothers made their own props why can't we !? Use common sense and be carefull . it can be done !C ya !Bob....." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[asra]

As a side note tonight I whipped out 2 blades to fit in my warp drive hub in about 2 hours all they need is fiberglassed and ballanced and the bladeshaft caps glassed in real good .... I was supprized at how fast it went when I just changed the shape of the blades a bit and did more free hand cutting with the table saw ... remember all I'm useing is a large sanding disk a table saw and a hand plane .... oh and a orbital sander ... if I can do it anyone can ! C ya !Bob......." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[asra]

If you have a warp drive why for the love of god would you **** about with wood its for cooking steak when your camping & look at all wood props the hub/center is the bigest section as this is where forces are at there greatest, carbon fiber is layed in continuous fibers you have cut/sanded through at the base this is where you have lost strength & this IS where they WILL break off sorry mate but please stop the madness & put your blades to good use to cook your steak

[asra]

I know that Butch S. I broke a Carbon fiber blade , I can't aford to go buy a replacement even if its only $150 bucks ..... so I need a replacement prop ... so ....I'm makeing one ... or two as the case may be ... 2 blades to replace the carbon fiber ones in the Warp drive prop, and 3 for the 3 bladed prop I made from scratch ...... I still maintain that the wood and fiberglass combonation will be strong enough to hold the prop togather at a reasonable RPM ...say under 4000 RPMwhich with my Rotex and its 2.58 :1 gear box will be more than enough the wood is 1.5" thick at the root end in the form of a large dowel its stronger than the wood further out on the blade by a long shot ... .... anyway ... thought you guys might be interested ... I'll let ya know how they work when I spin them up .... one way ot the other ! See ya !Bob.....P.s. I'm not asking for your opinion here guys ! I already made them ... just thought I'ed tell ya how I did it , I've already made one prop that spun up fine and have had no problems with it at all , just thought you might be in the need for a prop and short on cash .... make your own .... I have ! " Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "