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HomeScale✈️AircraftScale HeliScale Helicopter Main Discussion › Help on custom main shaft for trex 700
05-30-2011 07:41 AM  8 years ago
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vinceisip

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Fairfield, CA. - USA

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Help on custom main shaft for trex 700
I have a Huey UH1-C with Trex 700 mechanics. Anyone owns or work in a machine shop that understands our hobby? I'm wondering if someone can help fabricate a 12mm main shaft for the trex 700 that is about 40mm longer than the stock ones. Attached is a stock picture of the main shaft. In other words, the top section of the main shaft that I'm trying to achieve is 40mm longer. So it will be 138.8mm for the top section instead of 91.8mm and the bottom section will remain the same at 111.2mm. The overall finish total length should be be 250mm. I'm willing to send payment thru paypal if the cost will be reasonable enough for the fabrication/modification. Please let me know and many thanks to everyone's time.

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05-30-2011 04:08 PM  8 years ago
OTCP64

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Balto Md

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It looks like the only thing "special"about that shaft is the shoulder to eliminate a top collar.That is a lot of turning just to eliminate it.I would go with one of the many Vario choices and use a top collar.It was probably done to gain negative pitch for 3d purposes.If you can find the correct Vario shaft,you won't need a special shaft for future replacement.
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05-30-2011 04:47 PM  8 years ago
Mojave

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Palos Verdes, Ca. USA

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Only one issue here: Anyone can machine a mainshaft for you, but unless they have stainless stock that is very true, you could end up with a shaft that doesn't run true. These mainshafts are typically centerless ground (because of the length), to keep the runout to a minimum. I would agree, check out the 12mm shafts from vario and if need be, have a machinist relocate the jesus bolt and maingear holes. That's my .02
Barry
All helis and planes have an expiration date stamped on them...you only find it after you crash!!
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05-30-2011 05:35 PM  8 years ago
payne1967

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uk

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the shoulder won't be a problem
just get the machineshop to run a grove around the shaft at the correct location and fit a circlip and then shim to suit

the other thing i would do is to fit a third mainshaft bearing
the lower sceadu bearing housing will fit into the trex 700's frames
all you need is a bearing and to have the lower section of the mainshaft extended at the correct dia for the bearing
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05-30-2011 09:40 PM  8 years ago
OTCP64

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Balto Md

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Like the idea of the bottom bearing block.I don't know about grooving the shaft above the top bearing block,a collar is simpler.
You can get the bottom block here.
http://www.kdedirect.com/TREX700TBB.html
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05-30-2011 10:05 PM  8 years ago
Kona Chopper

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Kailua-Kona, Hawaii USA

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You can get some additional blade height by installing a Long FB style mainshaft and installing a Flybar sytle main rotor head which is considerably taller than the FBL head. You can still use align FBL washout base, probably all you have to do is remove the pins at the bottom of the FB head block. I measured the ADK FBL conversion on my 700N and from the top bearing block to the top of the head stopper its a little of 6" in height.

Why buy?? when you can borrow and no return
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05-31-2011 01:49 AM  8 years ago
vinceisip

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Fairfield, CA. - USA

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I will take everyone's opinion into consideration and see the best way to do the modification. If i have no luck, i will just have to stay with what i have and move on to another Huey project same size fuse but with 600 mechanics but use a 700 motor to run 12S 5000MAH. BTW, the torque tube conversion from skyhunterhobbys is holding up pretty good after 50+ flights. It flies smooth and the sounds of the 813mm edge blades are awesome. Thanks for all the response.
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