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Racing Video - 5/26/2005 6:19:47 AM   
SSAN



Posts: 446
Joined: 1/19/2002
From: Queen Creek, AZ, USA
Status: offline 		Check it out! There are some interesting videos from the web site below...
http://homepage.ntlworld.com/robert.ashley/teambananaracing/gallery.htm

Enjoy!

_____________________________

SAM-RAI... The Ultimate WOOD Q-500!
www.Sam-RaiRacing.com
       Post #: 1

RE: Racing Video - 5/26/2005 2:02:52 PM   
splatt



Posts: 651
Joined: 1/30/2002
From: splattsville, MN,
Status: offline 		I had my nose up against the screen trying to catch the smell !

One question to all, this is the second time I've seen where the helper holds the model until the moment before launch.

Are they kepping the engine from sucking dirt or trying to keep them cool on the line ?


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race, race, race. Racing toward my grave

(in reply to SSAN)
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RE: Racing Video - 5/26/2005 2:30:47 PM   
SSAN



Posts: 446
Joined: 1/19/2002
From: Queen Creek, AZ, USA
Status: offline 		Splatt,

It can be both ways, but mainly to keep dirt out due to the open venturi. To keep the engine cool, one would have to hold the plane of the ground with the nose pointing down instead of up. Pointing the nose up would go leaner, down would go richer etc.

Hope this helps.

_____________________________

SAM-RAI... The Ultimate WOOD Q-500!
www.Sam-RaiRacing.com

(in reply to splatt)
       Post #: 3

RE: Racing Video - 5/26/2005 2:34:50 PM   
splatt



Posts: 651
Joined: 1/30/2002
From: splattsville, MN,
Status: offline 		Cool, just trying to think if that would work to keep a Q40 cool enough on the line or having your partner risk his finger.

Stupid video, now I gotta try and work now, grrrrrr. I need to go buy a lottery ticket

< Message edited by splatt -- 5/26/2005 2:40:19 PM >


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race, race, race. Racing toward my grave

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RE: Racing Video - 5/26/2005 4:27:47 PM   
DHG


 

Posts: 896
Joined: 4/24/2002
From: Arvada, CO, USA
Status: offline 		Splatt,

By trial and error (mainly error), I have found that the Jett Q40 will be fine if needled for flight, then held off the ground with the nose down. Using the carb cools it too much, and it will run rich in the air.

The Nelson really likes to be throttled back until launch. I have the throttle and use it. My racing partner doesn't have a throttle so he wants me to use the finger method. So far, so good. I consist mainly of scar tissue and replacement parts at this point anyway, so I have less to lose!

Duane Gall
RCPRO

(in reply to splatt)
       Post #: 5

RE: Racing Video - 5/26/2005 5:27:03 PM   
garys


 

Posts: 782
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		Another thing with FAI is that usually the caller sets the needle at the last second before launching. Then engine is kept fairly rich until the last few seconds, then the needle is set. Some of them are just more comfortable holding the airplane off the ground, as it's sometimes aukward for a right handed launching caller to get to the needle when the plane is on the ground, because the needle is on the right side of the airplane.
GS

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GS

(in reply to DHG)
       Post #: 6

RE: Racing Video - 5/26/2005 5:34:25 PM   
splatt



Posts: 651
Joined: 1/30/2002
From: splattsville, MN,
Status: offline 		Thanks for the answer, how much work do you do to a Q500 "carb" and still stay legal for a Nelson Q40, gotta stay under 9mm for the bore, right ?

Can you dremel the top of it like a big open bell ?


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race, race, race. Racing toward my grave

(in reply to DHG)
       Post #: 7

RE: Racing Video - 5/26/2005 6:27:22 PM   
DHG


 

Posts: 896
Joined: 4/24/2002
From: Arvada, CO, USA
Status: offline 		Splatt,

Yes, you've got it. The rules for QM40 say it can be a carb or venturi, may be modified, doesn't have to be commercially available. I'd use a Jett one for the Nelson if I could, since it has an aluminum body and finishes up really nice, but the plastic Nelson one works fine.

First thing I do is drill and tap a #4 x 40 hole through the throttle arm and into a meaty place in the body, so I can insert a #4 x 40 x 3/8" steel bolt and pin the throttle arm in the full open position. (This is also helpful later, if I want to do a test run between heats and the throttle servo won't keep it open with the radio off.)

Next, I open up the top of the intake into a bell mouth, using a Vermont American router bit from the hardware store. I think I saved the packaging at home, so if you have any trouble finding the right thing, I can get the part number off that.

Third thing is to use a tapered reamer and work toward the midpoint of the throat (somewhere close to the axis of rotation of the barrel). I use a 9mm drill bit as a gauge and work slowly. If the drill bit squeezes through, I'm done. If it's close but not quite there, I use the drill bit to open up the hole to exactly 9mm. The plastic will stretch and deform slightly around the drill bit, so it won't open up past the 9mm limit unless you really ream it.

Finally, get a Dremel Moto-Tool with the tapered felt cone and polishing compound to smooth out the tool marks and rough spots. (Wear safety goggles, of course.) If there are any burrs or flash left on the barrel, take the barrel out and trim them off with a #11 X-Acto blade.

I even flare the bottom end a little to try and match the crankshaft opening ... I'm told that it makes no difference, but I figure it can't hurt. (If anybody asks, I tell them that it adds about 200 rpm. )

Repeated tach tests show no difference between a carb modified this way and the stock venturi. And there shouldn't be, since the shape of the channel the air "sees" is basically identical.

Put one together, we can do some formation 3D akro with 'em at the Nats!

Jack Stack

(in reply to splatt)
       Post #: 8

RE: Racing Video - 5/26/2005 9:04:32 PM   
luv to race


 

Posts: 490
Joined: 12/10/2002
From: Liquored, FL,
Status: offline 		Way too much work! I could drink a 6er', while you do all that for 200rpm....

smoke

(in reply to DHG)
       Post #: 9

RE: Racing Video - 5/26/2005 9:35:01 PM   
DHG


 

Posts: 896
Joined: 4/24/2002
From: Arvada, CO, USA
Status: offline 		That's my secret plan, to get you all relaxed & overconfident.

You are growing sleepy ... sleeeeepy ...

(in reply to luv to race)
       Post #: 10

RE: Racing Video - 5/26/2005 11:25:34 PM   
garys


 

Posts: 782
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		No kidding RB. Besides, if it's my airplane, I don't have to worry about MY finger over the venturi...and I'd rather drink the 6er' than risk slicing my fingers open while grinding on a carb...
GS

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GS

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       Post #: 11

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