Structural integrity of the RAF.

[birdy]

Just wunder'n wot the RAF frame/rotor head can handle.[]I recon i know now wot a Rosco can handle [][ anything but rotor strikes], but i wunder if theres a limit to the flog'n you can dish out to a RAF.I'v used it a few times to work critters and tho its alot slower to manouver, it can still do the same stunts as the little ferel, but for how long???[B)]The head for instance. On the ferel[ a Rosco] it's alot beefier than the RAF and its usual opperating weight wouldn't be half that of the RAF.My Raf could be thrown bout a bit harder than the average one coz its lighter [ -70 odd kg with the 914 and i'm only 75kg wring'n wet[].] and theres less artificial weight from the lowered TL[ only under power obviosly].I know they were'nt desigened to do anythn but putt round on cross countrys but even then you can get caught in some frame/ component stressing air[ especialy if there was a couple o fatys sitn init[xx(]]. Would the engineers have factered this in to the build strenght?, or did they think that noone would ever get caught in crappy air?[V]I'v never heard of anyone who 'throws his RAF about like a heavy feather'.Is there anything else i should consider, should i get the urge to wring its neck[}] besides structural integrity??Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Good question Birdy I have been involved in many discussions that end up asking how we got from Benson/Rosco light weight gyros to these 500kg monsters which have Double the thrust & weight without double everything ells eg. mast,rotor head,mast to keel attachment,BTW Dave Stubberfield & Rob Patroni have a rotor head designed for flying tanks

[Scott Hogan]

Hi Birdy, Bob,Well, Birdy, as you know I´m no light weight.The interesting thing about my RAF is that when I was doing a thrust test with a new prop, I didn´t notice any flexing in the airframe like I did with my single seater. It was very solid when tethered, even with 130 HP pushing the airframe through the keel.I found that I can crank it around like my single seater but not as radical of course. I don´t reckon you´re going to have any probs chasin those cows around the paddock.You can always get the ´bolt book´ out and look at the load you´d need to snap the Jesus bolt. Last time I checked, for a 5/8 AN bolt, it was about 18 tonnes, so a 1/2 AN would probably be......?a bl*??dy lot as well!Hoges

[Tim]

quote:Originally posted by birdyWould the engineers have factered this in to the build strenght?, or did they think that noone would ever get caught in crappy air?[V]What engineers?I am not overly familiar with a RAF rotor head but in most cases, rotor heads are way over designed. This is also what I thought of hub bars.Tim McClure

[asra]

Birdy, actually, apart from the Hub Bar, the Raf is well over built. That is why a Raf is so much heavier than it really needs to be, but it does make you feel good when doing rough strip operations.Ground wise you can use them on rough ground and things don't fall to bits. I always liked the solid feel of the Raf.I don't like the control rods being in compression when appying heavy amounts of "G" loading back stick. Raf had a good nose wheel arrangement and then changes it to a poorly designed nose wheel vertical. Several broke, but then Raf improved it to be bullet proof. Raf do have a habit of fixing things that ain't broke and failing to address things that are a problem!!!The one thing that really is a pain but not dangerous are the pivot points at both ends of the control gear that goes under the seat. Raf slide a 1/4" bolt through the 1/8" thick steel tang, then through a nylon scrub washer, then the 1" alloy and out through the secon nylon scrub washer and the second 1/8" thick steel tang. The steel tang holes wera elongated because they are left loose enough to allow stick pitch movement. You end up with a lot of stick slop that you have no choice over.What I have done to improve this situation is machined the 1/4" hole in the alloy out enough to fit DU bushed with an ID of approx 10 mm. I them make a sleeve with a 1/4" hole and the OD the fit the approx 10mm ID DU bush. This sleeve has to be a few thou wider than the 1" alloy and the nylon scrub washers. The scrub washers have to have the 1/4" hole drill out to the approx 10mm ID ofd the DU bush.This 1/4" bolt can then tightened like the teeter bolt and the sleeve wears on the DU bushes. No more slop.Hoges you are right. That lower mast with the timber in the top half of it is solid, and is a great roll cage arangement.I have seen the 2" X 2.5" tall masted gyros flex more than I would be prepared to put up with when taxiing on rough ground.[:0]Birdy, I reckon with the AK blades you could pull a lot of Gs for a lot of hours and not have much wear and tear, other than the above mentioned control slop scenario. If I remember I think you have done something simlar but I might be wrong.I have conducted over a 1000 hours on the same head bearing and it was still had the same clearance specs as a new one.Raf airframes are bloody strong BUT heavy.Aussie Paul.[]Aussie Paul.www.firebirdgyros.com

[birdy]

This is all good to hear[], next post you'll get from me will be skyt'n bout be'n the first to loop a RAF.[}] apart from the Hub Bar, the Raf is well over built.Thats why I don't fly them anymore Paul.[]And I agree, the RAF control setup is a c0ckrag sorta setup.Ground wise you can use them on rough ground and things don't fall to bits.Bloody ell Paul, the ridgid mains was the worst part of the standard RAF[!], have you ever tryed to TO from a corrigated road?[xx(]? [bloody thing woulda shook the **** outa a rock'n orse.]catchya after the loop.[]Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Birdy, Make sure you have a mate there with a video camera and a beer. The beer's for if you do it,the camera's for if you don't.Daryl Patterson

[birdy]

Wot, you don't recon it'll make it Daryl??Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Hello Birdy,Johnny Miller was doing it on a regular basis back in the 30's so you should have no trouble. When you succeed the video will enhance your reputation. If you fail and live we sell it to funniest home videos. If you die we use it in a training video in the "don't try this at home" section.Either way you'll earn the beer.Daryl Patterson

[asra]

quote:Originally posted by birdyThis is all good to hear[], next post you'll get from me will be skyt'n bout be'n the first to loop a RAF.[}] apart from the Hub Bar, the Raf is well over built.Thats why I don't fly them anymore Paul.[]And I agree, the RAF control setup is a c0ckrag sorta setup.Ground wise you can use them on rough ground and things don't fall to bits.Bloody ell Paul, the ridgid mains was the worst part of the standard RAF[!], have you ever tryed to TO from a corrigated road?[xx(]? [bloody thing woulda shook the **** outa a rock'n orse.]catchya after the loop.[]Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.Bloody ell Birdy, obviously you had too much air in the tyres!![] You are right though, suspesion on the Raf would be nice, BUT most people do not fly from corrigated roads. I got booked for using the road!!!Large tyres run half flat do well on most rough strips.A Raf is far from perfect BUT they are sturdy.Aussie Paul.[]www.firebirdgyros.com

[birdy]

"obviously you had too much air in the tyres!!"The front one's been dead flat for bout 3 years an the mains only had bout 5psi in um, and it was still rough.Am in the prosess of reconfigur'n the mains suspension ........ again.The setup i got onit now works perfectly, but its apperance may lead to confrontations.[ can't think who'd get upset by it tho.]The loop didn't work Darryl, I chickened out. 100' isn't a good starting hight.[ so you can keep ya beer]Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Birdy,The one thing that I have heard that would really concern me is the RAF rotor blades and hub bar. There have been several posts about cracks in the hub bar and the aluminum blades near the hub. Perhaps a "search" or question on the US Rotary Forum would help answer your question.The Sport Rotor blades and hub used on the Sparrow Hawk are strong as hell, but I would think they would not allow the fast flight path changes you need for your work - they are very heavy.Ken Rehler, New Braunfels, Texas USA - www.rvk-architects.com/ken/gyro/

[birdy]

The RAF blades were the first part o the machine i ditched Ken, I"v had Ozzy AK blades onit for years now.AK's are heavy, strong, fully extruded alu blades, and made by an Ozzy.Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.