Heavy AP helis [Archive]

GJestico

11-07-2006, 10:43 PM

Was the 6mm spindle a Raptor component? Did it bend just trying to lift a 12lb load? My interest is becuase my Raptor is currently flying at 14lb 4oz, 1.75lbs heavier than DJ's.

I know the Raptor spindle's are succeptible to bending during a hard landing, I've bent them myself, but I have a hard time believing you'll bend one flying AP maneuvers at 12lbs gross.

If you figure an 8lb Raptor flying 3D is capable of pulling 10g's, that's 80lbs of lift across the disc. That would equal over 5.5 g's on a 14 lb bird. I would be surprised if my normal style of AP flying exceeded 3 g's, and it's more likely in the 2g range.

Discussion started in this thread:
http://www.helifreak.com/viewtopic.php?t=23225

Continues here.

GJestico

11-07-2006, 11:03 PM

Not a Raptor part, the spindle I bent was a Century Raven spindle, from my first cam heli, an Electric converted Raven with camera mount.
The Raven And Raptor head components are very similar in size/strength, Both having 6mm spindles and same size bearings etc.

I am sure the spindle didnt bend from lifting alone. Some transient load from manuevering bent it most likely. The point is that load was easily encountered in very sedate AP flying . I dont 3d the thing !. Its never been upside down LOL.
I bent one spindle, then raplaced it thinking it was just a quirk. A few flights later I found it bent again, so I redesigned the head with a larger spindle. At 12 lbs and 700 blades at 1550r's I had found the limit of one part.

The key issue I believe here is head speed. I had my Raven geared for a ~1550 headspeed on 700 blades. I had done calcs that showed these blades presented less tension load to the head than the average 600 blades (as used in the 3d Raven) at 1900 rpm.
What I had not counted on and later determined was that all that tension load from small blades at high rpm helps to keep the spindle straight.
Think of the blades/spindle as a tightrope. Held tight at each end it can hold a certain weight in the middle and deflect a certain amount. Reduce the tension on the ends and add weight in the middle and it droops(bends) a lot more. I belive this is what happened.
This agrees with the experience of bending spindles during hard autos. Headspeed is at its lowest, so tension load is low. whats a pair of blades weigh? 13 oz. If those can bend it think of what a 11 lb wight can do at lower (relatively) headspeed
Full-size helis' blades will fold up in flight if headspeed is allowed to decay below a certain point.
I am often skeptical of how many G's can be pulled with a heli. its a different machine aero wise than a fixed wing, I bet the loads are under 5g for even hard core 3d flying. once again a guess that should be measured in real life.
So at what combination of high/low RPM, High gross weight and safety factor for emergency does it become dangerous ? that is the question I ask.

Greg

AZ ChopperCam

11-07-2006, 11:04 PM

I've thoguht about this alot in recent months. I see guys flying 620 sized Raptors so agressively it seems as if for sure the machine is going to self destruct. Maneuvers in excess of 10 G's I'd guess.

and they do this over and over again. It's these load/unload cycles that will fail metal parts. The centrifugal forces on a main rotor system swinging 710's at 1600 RPM is definatley not any more that 620's at 2200RPM.

I feel that a 6mm feathering spindle can handle 12 or 13lb all day long with AP style flying. 14-15lb is probably ok as well but at those weights I think metal grips and headblock is mandatory.

As was stated earlier.. yes a 600mm or 620mm blade heli can lift 12lb but auto ability is almost non-existant and if you're flying video there's another reason to not fly a 600 class heli... stability.

I'm going to sidestep the topic just a tad...I'm not saying 600 class heli's aren't smooth and stable, but the difference in the stability of a video shot between a 600mm and 680mm blade heli is huge. I've been there and done it and with nearly half my life as a videographer/editor I like to think that I'm qualified to make that statement. I now fly 710's and the difference between 680's and 710's is noticeable and makes a 600 class heli look like a small Trex shot it (not really but almost)

I would not do a true "professional" video job on anything less than 680's.

It's my opinion that you do not need a gasser to shoot most professional video jobs but rather a 600 class heli modified and stretched to at least 680 will do the job just fine.

as far as 6mm spindles go... for AP flying, you can load them up with 12lb every day all day and not experience any issues at all. I've been doing just that for the last 6 months with AP and years ago I was doing the same with scale heli's.

of course more flight time is needed for a definative answer and now that flying season is here I plan to do just that

GJestico

11-07-2006, 11:14 PM

BTW Im wearing 720's now on my "little" heli. Why are mine bigger than yours ? Genetics you know. :wink:

GGoodrum

11-08-2006, 12:49 AM

Oooh, you braggart! lol. :D

One point I didn't make earlier is that I like to run a bit higher headspeed in AP/AV setups. For the Raptor, with 620s, running it at around 1800 is still nice and smooth, but it gives a bit more lift, and has some "extra" power reserve in the kinetic energy from the higher h/s.

Same thing with the Logo 10. I run it at around 2000. It is smooth as silk at that speed, and as I said in the other thread, it has plenty of reserve power. It had no problem with the 9-1/2 pounds. We ran the a123 pack all the way down, forcing an auto, which was successful.

-- Gary

AZ ChopperCam

11-08-2006, 12:57 AM

wow! 9.5lb! :shock: I need to weigh my Logo 10 again. I've forgotten what it weighs but something tells me I was near 7lb.

If I start shooting with my Nikon 4500 and the fisheye I'm going to be close to 8.50-9.0lb on my Logo and I'm wondering if a 5s setup swinging 500's with the A30 is going to "hack" it.

rroback

11-08-2006, 01:54 AM

I can't understand all the forces involved in heli flight. I'd love to take my maxi joker to the next level, get the 800's up to maybe 1500rpm, or go for 900's at like 1300, and be able to carry weight no problem, but I'm worrying about the spindle. I can't figure out the sheer forces, which seem to bend the spindle, no problems with tension, although the bolts must be working hard.

rhett

MLaBoyteaux

11-08-2006, 09:27 AM

Greg,

Excellent reply. Very well spoken. It's obvious there are more forces involved than simple flight loads.

Having a group of pilots on this forum who take a step by step, cautious approach to "pushing the envelope" helps all of us fly safe.

Nitrospazzz

11-08-2006, 11:10 AM

It had no problem with the 9-1/2 pounds. We ran the a123 pack all the way down, forcing an auto, which was successful.-- Gary

9.5 lb and it still autos...WOW thats a lot better than I would have expected it to handle. I'm sure it wasn't an easy auto but it didn't drop out of the sky. Now I'm not so worried about it lifting my XT

askman

11-09-2006, 12:17 AM

biggest issue with large blade turning at high rpm is centrifugal load. bigger blade, more mass and radial velocity all contribute to it. I believe maxi is rated at 1300 or so rpm with 800? with 10mm main and 8mm feather.

lets look at vario benzine. Vario has whole table of recommended rotor blade/rpm combo in their manual. they use diameter, but I changed it to blade length. 600-620mm at 1700rpm, 660mm at 1600rpm, 700mm at 1500rpm, 760 at 1350rpm, 800nn at 1270rpm, 880mm at 1000rpm , 950mm at 900rpm and 1120mm at 850rpm. it runs 12mm main and 8mm feather. I've been told that these numbers are very conservative, by about 20% margin. looking at their 600mm spec at 1700rpm, I can see why.

looks like maxi at 1300rpm/800mm has similiar spec as vario, so I would think 880 at 1000-1100rpm would be possible. for going higher rpm, I think feather can handle it, but main shaft won't have lot of margin. I think you can run 830 at 1200, which may be pretty good setup. frankly, going really low headspeed on joker2 is tough due to gearing and motor combo.

MLaBoyteaux

11-09-2006, 08:29 AM

On my Vario, I use 1300 as a max on my 810's, but normally shoot for around 1250~1275. On my Condor with 810's I run it at 1300.

I think the Vario limits are due to the plastic grips. The Condor also uses plastic grips. The Condor and even the Bergen Observer uses a 10mm main. With the Kasama metal head, I think the weakest piece on the Raptor head is going to be the feathering shaft. Not that it's going to fail, but that it will be easier to bend during a hard landing with low headspeed or in some of the scenario's GJestico has suggested at the top of this thread.

With the 660's on my E-Raptor, there seems to be a sweet spot for the whole heli at around 1650. Below or above 1650 and it seems to excite other parts of the airframe/mount into resonance.

I just ordered a pair of the 680 semi-syms with 3° of washout to try out. I'm comfortable putting these blades on the Kasama head.

I see there is a MD-500 Scale fuselage kit for the Raptor 50. I think DJ was interested in getting one. What would an electric Titan Raptor with one of these scale kits weigh, AUW ready to fly?

I'm trying to get the AUW on my Raptor under 14lbs with the Rebel XT camera. I think I can do it, I'm within 4 ounces right now.

AZ ChopperCam

11-09-2006, 09:00 AM

I see there is a MD-500 Scale fuselage kit for the Raptor 50. I think DJ was interested in getting one. What would an electric Titan Raptor with one of these scale kits weigh, AUW ready to fly?

yup... it's an MD530 (pointed nose) I ordered one and am putting a converted E-power Titan in it. They are supposed to be about 8.5lb with electric power.

when mine is done I'll weigh it.

askman

11-09-2006, 10:57 AM

you are probably right Mark. I was told by ASI, who makes vario copies that they are running 1100-1200rpm with 1120mm. with their aluminum grip. I was also told that NRI was using vario head on their test heli at higher headspeed.

GGoodrum

11-09-2006, 11:56 AM

I have always used the metal hub and hardened main shafts on my 3D Raptors, but haven't bothered using the metal grips until recently, when we started running headspeeds up around 2250-2300. A 620-bladed Raptor with +/-13 degrees+ of pitch has some an ungodly amount of power (with a Z50-600 and a 12s-3300 FP Evo 20 setup we were getting 3900W+/97A peaks...) at that rpm. After playing with that much power, I just can't see how ANY AP/AV setup I can come up with is going to put anywhere near the same sort of loads on the head/.grips/spindle. I can definitely see, however, how a lower headspeed, with a heavy load, can be hard on spindles.

I'm still liking my 620-bladed eTitan at 1800. It is VERY smooth, has plenty of power/reserve and autos just fine. This weekend Andrey is going to make the first of the larger 360 Pan-LG mounts. I plan on testing it with a Sony a100 and a super wide-angel lens. With a 10s2p setup of a123 cells the AUW should be around 13 pounds, or so. I don't expect to have any problems. :)

-- Gary

askman

11-09-2006, 01:27 PM

I think heavy slow blade effect on spindle is greatest at landing. obviously it can handle the weight of heli at high G maneuver. hmm, hardened spindle should help a lot for this type of load.

I am trying to catch up with all my outstanding orders, and do the raptor. I am going to finish coding it up this week, and cut this weekend. may not get it finished until monday/tuesday though. just too busy. I really need to improve my process flow. I just ordered several hundred bucks worth of pulleys and belt though. final assembly is what kills me, but in many ways, the pancam design is simpler to assemble compared to my other designs.

AZ ChopperCam

11-09-2006, 01:29 PM

final assembly is what kills me

I hear ya there! That's the part I hated most about selling RaptorCam mounts.

askman

11-12-2006, 01:31 PM

fitenfyr

11-12-2006, 06:02 PM

Somebody once posted something (I know I am so helpful...:D ) about hardening making spindles/mainshafts brittle.
So instead of bending you get breaking.
Anybody a metal expert out there? :D

I think I would rather have the bending than breaking myself.

askman

11-12-2006, 06:58 PM

heat treating can make it brittle, if done improperly or with wrong metal. with correct heat treat and tempering, it will be ok. look at spring steel or piano wire, very hard surface with soft inside. of course it needs to be done after machining. if you purchase hardened spindle from the manufacturer, you should be pretty safe.

AZ ChopperCam

11-12-2006, 07:30 PM

askman

11-13-2006, 12:03 AM

longer shaft should be easy. precision ground drill rod is easy to get in 10mm. since they are not heat treated, it is actually pretty good main shafting. just have to drill the two holes. it could even be heat treated. (but cheaper to heat treat in batches, rather than few)

GGoodrum

11-13-2006, 01:08 PM

one thing not being discussed here which deserves more discussion than spindles or main shafts is Jesus bolts and clamp rings.

One of the things I hate about loading a Raptor 50 up to 13lb is the fact that if the lower Jesus bolt shears the head departs the aircraft rather quickly. I'd like to see a longer main shaft that has a clamp ring below the auto hub so that if the Jesus bolt did shear it would result in a controlled auto and not parts falling from the sky.

A buddy of mine has a CNC lathe that he makes trumpet mouthpieces on and I've been begging him to make me a longer shaft for a while.... I need to beg him some more.

DJ --

Are you using the metal hub, shown below? It comes with a clamped collar that goes on the bottom of the hub, below the "Jesus" bolt:

http://www.tppacks.com/photos/PV0484.jpg

http://www.tppacks.com/photos/PVO492.jpg

As I've said many times, I think for hard 3D and for heavy AP/AV use, this upgrade (PV0484) should be in the "must have" category.

-- Gary

AZ ChopperCam

11-13-2006, 01:24 PM

No I am using a Kasama head which has 2 clamping screws. It's not the head Jesus bolt that concerns me it's the lower Jesus bolt. I pulled mine last night to have a peek and the holes in the auto hub sleeve are elongated. Time for a new auto hub sleeve.

I'd like to see a 3.5mm Jesus bolt and clamp ring below the hub. That'd make a great, strong and safe configuration.

dreslism

11-13-2006, 01:27 PM

Gary,

I think DJ was refering to the bottom Jesus bolt for the main gear, not the one up top.

Up top, DJ, Mark, and myself are running Kasama heads with clamp the head to the shaft, so we are OK up there.

Talking about the bottom one, so that is where the reference to the longer shaft is from as you could put a clamp on the bottom then.

GGoodrum

11-13-2006, 05:17 PM

How about a stronger steel screw, or a hardned pin with cotter pins?

In all the 3500W-4000W Raptor setups I've ever done, I have never had a Jesus bolt shear. Not once in four years. Maybe the slower speed you guys are running is as hard on the Jesus bolts as it is on the splindles. :)