Balancing a Warp dive Prop?

[asra]

Can anyone let me know the best method to get a warp drive prop into balance? Having been told everything from lead shot drilled into the ends to lots of hairspay on the lightest blade...your experience would be very much appreciated.The chips have just been filled and its now a fair way out as you can see.DaveImage Insert: 32.85

[NiqueNaque]

Ooooo...It is a two blade? Can't see from this angle.My cure for a timber prop:1. Base plate - 200 x 200 x 10 steel plate2. Spindle - M 10 x 150 bolt, nut and washer3. Centre plate - 150 x 150 x 2 alloy plate4. bag full of 1/8 ball bearings.5. Bullseye levelMethodrill and tap the 200 base plate at its centre to take the M10 bolt.Screw the nut onto the shank of the bolt, put a washer between it and the base plate, screw the bolt into the base plate and tighten it to snug, cut the head off the bolt and then cetre pop the cut end, drill it with a 1/4 drill so a rebate exists in the top for a ball bearing to sit in.Mark out the alloy plate on the centre [from diagonals] with the PCD for the prop and centre pop the middle and drill to 2mm deep with a 1/4" drill, mark two bolt holes diametrically opposite and drill to take the propeller mounting boltsBolt the alloy plate to the propPut a bearing on top of the bolt and base plate in the drilled recessPut the prop on the spindle and make sure it engages the bearing at centre, it will click as you roll the prop over the engagement points.Place the bulls eye level on the plate at it centre and see how far out of level you areGet some 'known' weights and add them to the weight of the highest blade, note the weight and the centre required to being the prop into balance.Modify your blades to suit, with my timber two blade prop I had to shave about 10 g off the leading edge of one blade and same for the tail edge of the other, I also had to take about 60 g off one blade all over, result was a very smooth prop.Here's a sketch:Image Insert: 3.02

[asra]

Thanks for all the detail Nic. Sorry if I wasn't clear as I thought Warp Drive props were all Carbon fibre. Mine is a three blade ...here's a better pic. Image Insert: 62.18

[NiqueNaque]

Dave,It is equally as applicable, the bullsewy permits you to see how you're progressing if you add wieghts, initially by using coins at various centres to balance it up.With carbon fibre it is probably not a good idea to remove material, so adding it is better, in which case you will want to add weight to the lightest blades, you can do this by adding coats of resin or paint, even lead shot if you can find a place to poke it. I strongly advocate that you try weigh each blade, and each end of each blade and try make them all the same before you try them in the hub on the balancing jig suggested. If the hub is balanced and the blades weigh the same and have the same COG, the prop should be close to balance.Cheers,Nicholas TomlinAlarmist - www.alarmist.com.au - we scare for you

[asra]

I have to Agree with Nique Naque here,ballance each blade at the exact same point in each blade 1/16" makes a big diference ! so be exact !then when adding weight later add it at the same ballance point you used previously, ...not at the end of the blade or this will throw off the individual blade ballance,.... this is the same method you use to ballance a rotor blade, and it had worked extreamily well for me !C ya !Bob......ps. I painted my 2 blade warpdrive prop with reson to ballance it and it worked well after repairing it , and it was out alot further than your blades. but I found I had to individually ballance them over again till all worked fine." Momm'a alwayse told me , Son the impossable is only a little bit Harder... and ya know I do believe She was RIGHT ! "

[Brian]

A tin of spray paint is what Rosco uses to balance a prop except he balances the prop upright using a shaft in a vice and gives the lighter blade an extra squirt of paint to balance it, looks simple watching Rosco!Should not be necessary to use any weights other than layers of paint !BrianPooncarie NSW

[asra]

thank you Brian ! I ment to mention that usually just a few layers of paint will ballance the blade...it doesn't have to be reson ! good point !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]

By the way, I broke one of my Carbon fiber blades when I ever so lightly flopped my gyro over the first time and the engine was still running and it snapped off a prop blade almost in the middle of the blade...I was going to send for another blade but desided to try and repare it first...to my supprise regular fiberglass repaired it just fine and after many hours of grinding and laying glass and grinding again i finally got it back up to shape again...but it was a bit heavier than the other blade.... so I sanded the other blade and then added a coat or two of reson on it and got it to the same weight as the newly repaired blade.... i went through the tedious steps that Nic pointed out already and put it all back togather on the gyro with zero pitch and after warming up the engine took it to 6500 rpm for about 45seconds or so .... having survived that ok with no signs of letting go I set the pitch to max pitch that i could get and still reach 6500rpm though for a while I ran it a bit too steep and couls only achieve 6400rpm... but later changed it .I don't recomend repairing a carbon fiber prop blade like this , after all the replacement blade is $150.00 and will be matched by serial numbers to get you the proper weight blade... but if your short on funds like I was then it is an option.......incidently this last crash broke the same blade at or near the same place.... I am debateing repairing it again.... but I don't think I will, as I am makeing a solid woden prop now for it .... I'll replace the crbon fiber blade at some later date when i have the funds.....just so you know you can repair a carbon fiber blade with fiberglass reson and cloth ...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 ! "

[Mark Horan]

dear bob,Ill give you a tip, dont try to repair carbon fibre prop blades. ever had one fly to pieces at max grunt? first thing that happens is the stick tries to go backward and forward really, really, hard.This almost makes poo come out of your bottom.next thing that happens is you pull power off really quickly so that your now unbalanced gyro doesnt shake itself into all of its individual component pieces.Poo goes back in, where it belongsif you are really unlucky, the bit that departed your propellor doesnt flutter harmlessly toward mother earth, but instead has attached itself to your beloved rotorblades (the bit that holds you up with the birds). This is the point that the tricky bit of propellor has turned itself into an airbrake and your gyro starts to fly? sideways toward the hard bit beneath the sky.Poo comes out again with little chance of retreat.Luckily, Marky boy had some good training,and remembered the old adage "airspeed is good" When one is at 300 ft and approaching the ground in an unconventional way it is really difficult to push the stick in the direction that your brain tells you is going to really, really hurt. But the increase of rotorspeed flung the offending member off the rotors and I got control with about thirty feet to go.Although not enough control, the rotorblades struck the ground on the lefthand side, the mast snapped and gravity did the rest (with a little help from his friend momentum)I think it was a 9 second crashall this from a prop that didnt even have any visible damage, however, was parked in a carport for several years before I bought itDONT fix broken carbon fibre props. If the strands inside them are broken, they WILL fly to peices....throw them away, new ones are cheap. When a crash costs around a thousand dollars per second....they are real cheap.(so is training)Regards, Mark.

[Mark Horan]

For those of you who were wondering?.....The poo went back into hiding when it saw the ground comming on the second sommersault.Mark

[NiqueNaque]

Markus Horribulus,Most amusingly presented, sounds like one of the best saves ever and well done..can we please have this in the what [not] to do thread? I'm sure you can add the right invective.Was the prop directly exposed to sunlight for all the years it was in the carport? I recall a fellow telling me that epoxy breaks down with UV light.Cheers,Nicholas TomlinAlarmist - www.alarmist.com.au - we scare for you

[mrford61]

What makes the stick go forward really hard from a prop blade breaking?

[asra]

Advice taken Mark Thank you MrFord61... another Mark I would amagon the sivire shakeing of the entire frame when the prop departed rotateing the frame back and forth about a foot each waywould account for the stick shake , Definately a scary sinerio, though I did repair the carbon fiber prop and it did hold untill it struck mother earth once again , there is little sense in having your Aircraft self-distruct in flight . I expect Marks engine on his gyro is a direct drive, just suspect it ,as they turn alot faster than one with redrive/reduction units.turning a prop slower has many advantages the least of which is prop survivability. I remember reading years ago about a good high quality wooden props hooked directly to a large Volkswagon powered Gyro in Las vagas the man was testing his NEW prop, and it came appart while still on the trailer... luckily nobody was hurtbut I think property dammage was insued, as the blade went through the kitchen door . anytime you spin something realy fast its down right dangerous ! Most props now days have a limit to which they should be spun at . the max RPM at which they have been tested at ... exceed it at your own perral ! I think with Marks Hands on experience though , I will definately replace the old twice broken blade now..(.Grin) its paid for itself already ! hehehehe Thanks Mark for your relateing the experience ! i can see why you are so adimate about prop repair now ! , i think I would be too ! 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]

quote:Originally posted by Bob K.Advice taken Mark Thank you Most props now days have a limit to which they should be spun at . the max RPM at which they have been tested at ... exceed it at your own perral ! 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 ! "Bob, for your home grown solid timber prop, may I suggest 150 rpm!!![]Just joking. I think you should limit that prop to 500 rpm. That way it won't fly apart, you won't get off the ground, and you won't crash!![^]Remember that gliding it first is your only chance of success.Aussie Paul.[]www.firebirdgyros.com

[asra]

Howdy Paul ! Well , I understand your reluctance to trust a home made prop, even though its made of wood like so many others.... if my first prop is any example , and i believe it is .... it will do fine even at 2,519rpm max ( thats the prop RPM at max engine RPM of 6500 with the 2.58:1 gearbox)this prop I am makeing now is laminated(2 layers) if that makes you feel any better actually it makes me worry a bit more I don't trust laminations very muchbut I plan to hedge all my bets with a coat of fiberglass cloth/reson just to be on the safe side.... to be quite Honnest with ya I am looseing intrest in the darn thing.... but I will perservier .!if this darn snow would melt maybe I could get something done ! anyway my first 2x6 prop worked out fine .... ran it at max throttle for quite some time testing it , and props are not that hard to make so i will make more when and if I need them ..... I don't want to hijack this thred so I'll start another one on that subject 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 ! "