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Old 12-09-2008, 09:55 AM   #41
Matt Jenner
 

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It all depends on your head, and size of the bolt in featherin spindle as it is this that keeps it all together..

There is a formula that Bell bloke taught me and i have forgotten some of it, where you can work out your disc area, take into account the weight of your blades and the head speed you want to run, it will give you the pulling weight of the blades at a certain RPM.. it is a technical way of doing things.. and wont be everyones cup of tea ( to use a british saying)

But if you are into camera work where you have thousands of pounds worht of equipment hovering around then these figures are what some do to ensure they are flying safely and within the limits of the machine..

For example, a predator head may be tested to say 400kilo...
well i know spinng 810 at 1550 i am pulling 300kilo, so i am in the safe zone...


most would run between 1450 and 1580, of course you can run slower..

Matt
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Old 12-09-2008, 10:05 AM   #42
Peter Wales
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OK, Ross beats me again, but I dont really believe him cos he says he doesn't have to start the engine but it uses a little fuel. Whats that for Ross?

On a more serious note, for simply hovering and cruising around I use 1350 rpm. For a little more adventurous flight, but nothing inverted like a loop or roll, I'll go upto 1450. For basic aeros like loops rolls and simple flips I'll go to 1550 or 1600. If you only want one headspeed then generally 1450 - 1500 IMHO will cover everything but you may need height and speed if you try a loop.

Just for the record, I have my pitch setup at -3,5,12 for normal at 1350 and idle up 1 at 1550 and -12+12 at 1750 in idle up 2.

I have been flying turbine pod and booms longer than just about anyone else in the world, and have probably done LESS total flying time with them than Ross does in a month. I'm kinda set in my ways, know what works for me and cant be bothered to try anything new. My first turbine came with NHPs and my first 2 stage had them and I was advised by the manufacturer not to go as daft as the other person who had them who was flying at 1900-2000 rpm. This was using a Wren and of course the headspeed was totally out of control

Anyway, they ran fine at 1750 and I've stuck with them ever since, and I either put orange tape on the tips so I can see them or BUY THE WHITE ONES
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Old 12-09-2008, 10:10 AM   #43
Matt Jenner
 

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Anyway, they ran fine at 1750 and I've stuck with them ever since, and I either put orange tape on the tips so I can see them or BUY THE WHITE ONES

Interesting info Peter, i did not know they did white NHP's, i have only ever seen black... but then i havent bought blades from US...

Matt
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Old 12-09-2008, 10:59 AM   #44
Skiddz
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Quote:
Originally Posted by Bell Bloke View Post
Stacks of 'hang time on the MAH G2 blades, infact you can land and take off again. :-)
haha.. Reminds me of my 1st flight in an R44.. Did a full down, picked back up and did a 180 pedal turn and set it back down again - all on inertia. Can't do that with an R22.

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Lord it's getting a bit deep in here, I need my wellies.

I can do an auto with my NHP's, land and leave it for 10 minutes with the engine off and then still have enough energy to take off, do 3 1/2 flips and land inverted
Time to break out the flag! Like Chris said, I'd like to see video of that!
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Old 12-09-2008, 11:21 AM   #45
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They are black with a white vinyl covering on them. In the early days thay all came with the vinyl but no one could get it on nicely without air bubbles or lumps in it so they offered to do it for you.

It's not a nice gel coat tho'
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Old 12-09-2008, 12:03 PM   #46
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Matt, the Century head fails at over 650kg with the help of a heafty yank on the controls.
Thats pretty mental and frightening when you think about it. :-)
The highest recorded load that I found in my straw poll on the Century forum was 319kg.
Don't want to start anything, but just thought the figures were interesting.
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Old 12-09-2008, 12:20 PM   #47
Matt Jenner
 

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Interesting Bell,

I did not know the max weight, i was using 400k as an example, 600kilo plus, WOW,
when you say the head is rated, at x amount, do you mean the M4 bolts on the spindle or the actual head itself

Matt
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Old 12-09-2008, 12:50 PM   #48
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The feathering shaft is the weakest point, it's the cap screws that fail at that point.
I think we are sending folks to sleep now...... :-)
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Old 12-10-2008, 07:10 AM   #49
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Quote:
i had a choice of either the V blades or the MAH 810 and decided to go with MAH they came very well balanced and with matching c.o.g. infact i didnt have to alter anything except the tracking. one point i will make is im glad i didnt go with the V blades because an all black blade is harder to see than a white one. luckily the MAH have white tips.
Vblades are also balanced and have the same COG. They also have reflective tips and you can see the rotor disk pretty good. They aren't all white so there is a difference, but they are definitely better then all black. I run the Vblades 810 at 1,680 doing aerobatics with no problem. There isn't really anything wrong with NHP, but as noted they seem a bit softer and don't have the pop of a Vblade (not that I'm looking for a pop in the turbine).

Lou
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Old 12-12-2008, 02:50 PM   #50
helibeli
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If you're going to fly the Predator with 850+ mm blades, should'nt you be dropping the number of teeth on the primary pinion gear or is this no big deal for the Wren?What is the turbine RPM in the hover with 710 and 850 blades?
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Old 12-12-2008, 05:05 PM   #51
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Quote:
haha.. Reminds me of my 1st flight in an R44.. Did a full down, picked back up and did a 180 pedal turn and set it back down again - all on inertia. Can't do that with an R22.
Out of interest, was that with the torque or against?
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Old 12-12-2008, 05:25 PM   #52
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I guess "lack of pedal" turn would be more apt as I went "with" the torque. The flare brought the RPM to just a hair under the red line on the tach and the skids JUST touched before I pulled pitch and turned around with the low RPM horn blaring away. Second setdown was right at +/- 80% on the tach with the collective in my armpit.
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Old 12-12-2008, 07:33 PM   #53
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Having never auto'd a 44 I was just curious as to how it would go against the torque on a relift. 47 takes some beating.
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Old 12-12-2008, 10:34 PM   #54
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I didn't even want to try to the left. Autos in the 44 are almost a non-event. A 90knot, 90% auto has a glide ratio extremely close to a heavily loaded Cessna 172 and there's quite a bit of hang time at the end for set down. I just wish I could afford to fly one more.

I'd love to get some time in a 47, but I don't know of anyone around here operating one...
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Old 12-13-2008, 04:43 AM   #55
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'Good Hang Time' on the 44? Are you useing V blades on that?
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Old 12-13-2008, 12:12 PM   #56
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Quote:
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'Good Hang Time' on the 44? Are you useing V blades on that?
hehe, I'm not sure. I'll ask Frank Robinson when I see him at Heli Expo in February.
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