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HomeScaleAircraftHelicopterScale Model RC Helicopters › Gazelle - Blue Thunder scale rotor head
03-06-2012 02:16 AM  6 years agoPost 1
heliadictaholic

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Hobart, Tasmania - Australia

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Hey guys.

I have been drawing in 3D, a scale rotor head for the 700 BlueThunder and Gazelle helicopters (will also suit 800). Hope to have some CNC machined.... Have a look at the attached 3D image to see where I am with the drawing......
....But...., I have a problem... The rotor head will look scale but obviously will not operate as the full size version..... The Gazelle/BT rotor head has a lead lag damper - the scale model has a fitting that looks like the lead lag damper.. The full size rotor blades have 2 mounting pins and a separate main mounting pivot pin, the scale head has only one main pin - the blades are fixed differently to the full size version. My problem is, I need to be careful that the blade does not hit the "look alike" lead lag damper main mounting pin during blade lag. Can anyone tell me if they have any idea on how much a blade will "lag" under normal operation. The setup that I have will allow about 120mm lag movement at the tip of a 700 blade, before the blade will contact the lead-lag "damper" main pin. I have never observed blade lag - start up could be a problem if starting too fast....

There is another issue, if the heli is involved in an accident, the blade will be forced back into the damper main mounting. I think I could use aluminium tube for the lead-lag mounting pin. This pin should deform and release allowing the blade to move back in an accident and hopefully minimise damage to the head.

I have printed in 3D, some test pieces to check the fit - see pics...

Does anyone have any advice they can provide?

IF ANYONE KNOWS OF A SCALE GAZELLE HEAD ALREADY AVAILABLE FOR 700-800 - CAN YOU PLEASE LET ME KNOW... I FOUND A LARGER ONE - FANTASTIC LOOKING HEAD, BUT WAY TOO BIG FOR MY 700 BLUE THUNDER. I AM STILL DEVELOPING THE 3D MODEL - HAVE NOT PRODUCED DETAIL DRAWINGS YET...
H

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03-22-2012 01:19 PM  6 years agoPost 2
heli-nut50

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Oil Springs, ON, Canada

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You could try Peter Whales if anyone would know he is the guy. His web site is http://scalehelicopters.org/ hope that helps.

Clayton Brown
MAAC#49470
IMAC#6464

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03-22-2012 03:49 PM  6 years agoPost 3
coptercptn

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Mesa AZ. USA

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how about, build the scale head for display, and fly it with a more conventional (read; commercial) one?
Also, if you are worried about the integrity of the head after a crash..? I think that would be the least of your worries

Home of the "Sea Cobra".....

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03-22-2012 06:25 PM  6 years agoPost 4
R.J.

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SF bay area, CA USA

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I don't know how much the blade will lead-lag. Probably will be largely dependent on how tight you mount the blades.

I like the idea of the aluminum tube to shear, or a nylon bolt to shear, but what about either not putting in a pin or using Neodymium magnets to hold the damper in place so it could easily swing out of the way if the blade lags too much.

Nice work on the head! Don't know if it's necessary to beef things up a little over true scale for strength. I guess you have to run one of those finite element analysis programs that I know nothing about.

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03-23-2012 10:48 PM  6 years agoPost 5
heliayto

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solihull, uk

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From a full size perspective which also equates to our models to a point, it depends on the loading of the head, this will vary on the all up mass, head speed, manoeuvre being executed and a few more aerodynamic factors.

Generally it is measured in degrees rather than a linear range as per 1inch/25mm. It is rather small. The thing to be careful of is the initial spool-up when the head speed is low. Additionally be careful not to over tighten the lead lag hinges/bolts or have them to loose.

Hope this helps.

Regards.

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03-24-2012 03:37 PM  6 years agoPost 6
Mojave

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Palos Verdes, Ca. USA

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I have been following this thread, you have a very nice piece in the works! By doing the rapid prototype parts you'll be able to overcome a lot of the obstacles and fitment issues. As far as the lead/lag issue is concerned, all you can do is set the ESC on soft start and give it a try. In the event of a crash, you are flat out screwed no matter what you do. So I wouldn't approach this from a crash standpoint, but from more of a functional angle.

I hope you have a machinist buddy that can do this head for you, because it's extremely time consuming/expensive to program and fixture this job for a run of only a few parts. I would plan on a production run of at least 100 units (after the prototype design is proven)or the job shops won't even touch it. Good luck and keep us posted!
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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03-24-2012 03:57 PM  6 years agoPost 7
coptercptn

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Mesa AZ. USA

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Barry , I thought you had your own CNC shop in your basement..?.. No?

Doesn't everyone..?

Home of the "Sea Cobra".....

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03-24-2012 05:07 PM  6 years agoPost 8
Mojave

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Palos Verdes, Ca. USA

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LOL, nope I don't have a basement My bud has a 3 axis CNC in his garage and I use the machines at work when the boss isn't looking...
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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03-25-2012 01:28 AM  6 years agoPost 9
heliadictaholic

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Hobart, Tasmania - Australia

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G'day guys, I am converting my mill to 4 axis CNC - I have the drives, electronics and waiting for the anti backlash ball screws to arrive.... But my major problem is that I am not a machinist - I am a 3D draftsman. I think I would need a lot more machining knowledge before I could attempt this project on my mill..... I will be able to make my 2.5mm aluminium side frames that I use in my scale helis.

I have been in contact with a guy on CNCzone.com who is going to give me a price to manufacture the parts.

I have also been talking to justscale.co.nz. "Justscale" has a contact also who may be able to help. If their contact is interested, we should be able to get some production happening.

If any of you guys know someone who has hobby CNC gear, can you let us know. It would be good to get as many feelers out there as possible.

I have 3D printed all of the plastic test pieces see pics... Some parts do not scale down too well - I am using 2mm I.D. ball races in the swash lock hinge and they are still too big to look scale. Something we have to live with I think. The swash lock hub also has a thickened section at the back so to allow us to balance the head. I have also designed the swash to match.

I will be testing the movement in the next couple of days. I will let you know how it goes.

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03-27-2012 05:34 AM  6 years agoPost 10
El Bucho

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VA

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Where did you get the rod end bearing for main rotor pitch arm?? Been looking for something that size for a while. Not the the bearing, but the whole rod-end. Thanks!

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03-27-2012 05:40 AM  6 years agoPost 11
heliadictaholic

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Hobart, Tasmania - Australia

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Spare part for the Super Scale rotor head... Have a look here:
http://www.justscale.co.nz/catalog/...products_id=380

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01-21-2013 11:50 AM  5 years agoPost 12
heliadictaholic

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Hobart, Tasmania - Australia

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This post copied (with edits) from another on of mine on RR.....

I have been looking for someone to make a BT/Gazelle scale rotor head. Some of the prices were coming in at around the $3000 mark... Forget that - way to high....
Anyway I decided to modify the hub part of the head - converted from 1 piece hub to 15 separate parts to make machining easier and found a company that could produce the head for around $1000 for 1 head (does not include shafts). This is still extremely high cost and I don't think there would be enough of a market to "mass produce" the head.
So far I have had the hub, hub side plates and 3 grips CNC machined. These few parts cost $429. I will order more parts soon...
Here is a picture of the CNC parts so far.
I will buy parts for 2 heads - may have to spread the cost over a couple of months to sneak past the "fun Police"

I will post more pics when I can....

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04-02-2013 11:05 AM  5 years agoPost 13
heliadictaholic

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Hobart, Tasmania - Australia

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CNC Gazelle/Blue Thunder rotor head
G'day guys,
Finally, I have all CNC parts for my Blue Thunder CNC head.... The cost is a bit high but I think the result is worth it. For example, the blade grips cost $64 each, grip brackets $46 each...
I had the complicated parts made in China and I made the simple parts on my lathe and mill.
The feathering shafts are cut down Trex700 feathering shafts.
I bought the parts a few at a time, this way, it is not so much a hit on the back pocket....

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04-02-2013 11:29 AM  5 years agoPost 14
hootowl

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Garnet Valley, Pa.

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That is super cheap for machine work if you asked me. And why this country has lost it's machining industry.

Nice job on the design and outsource collaboration.

Wolves don't lose sleep over the opinions of sheep

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04-02-2013 11:51 AM  5 years agoPost 15
slickporsche

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American/Philippines

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Gazelle - Blue Thunder scale rotor head
heliadictaholic Vario has a couple of multi blade heads that use no lead/lag. They use two bolts per blade. They claim it works great. So your idea of dampers should be really good. Outstanding job by the way! Years ago, I used to spin up my rotor head slowly at first, and then slowly let it slow to a stop. Then, I would lock the blades in that position. That also worked great.

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04-02-2013 09:17 PM  5 years agoPost 16
R.J.

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SF bay area, CA USA

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Looks really nice. Let us know how it flies.

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04-03-2013 04:24 AM  5 years agoPost 17
teamdavey2001

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Sunnyvale, California, USA

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Oh man

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05-11-2013 08:46 AM  5 years agoPost 18
heliadictaholic

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Hobart, Tasmania - Australia

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G'day guys,

Head now painted. Pretty happy with the result...

I eliminated the normal bolt through the head and shaft. My setup has a hardened pin light press fit through the head and shaft - this fit is covered by the swash follower base which slips on, then tightens onto the bottom of the rotor hub.

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05-11-2013 01:23 PM  5 years agoPost 19
Mojave

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Palos Verdes, Ca. USA

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That looks great! All it's missing is the grease streaks Where did you get the cool little rod ends from the swash to the grips?
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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05-12-2013 12:38 AM  5 years agoPost 20
R.J.

rrVeteran

SF bay area, CA USA

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Looks fantastic! Well done.

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HomeScaleAircraftHelicopterScale Model RC Helicopters › Gazelle - Blue Thunder scale rotor head
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