.25FX Viper mount  
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All Forums >> RC Airplanes >> Pylon Universe - RC Pylon Racing >> General Racing Discussion >> .25FX Viper mount
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.25FX Viper mount - 12/21/2007 11:45:00 PM   
Duane-RCU



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Probably has already been done, but I wanted a different way to mount the .25FX on the back plate. Because of the remote needle, you grind or space it. Some use spacers or washers, the first one I used a nylon mount. Then I found plate aluminum, and a hole saw...


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RE: .25FX Viper mount - 12/22/2007 2:01:38 AM   
gunfighter


 

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From: Canyon Lake, TX, USA
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Nice job Duane!
Since the viper / Predator always comes out tail heavy with the OS and similar .25 engines, I have always used the Dave Brown 202L glass mount and bolt it to the backplate mount. Saves adding weight.
Are you going to fly with the Thunderbirds / TX Wings group this year? If so, I will see you there!
Chuck

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RE: .25FX Viper mount - 12/22/2007 2:25:43 AM   
vicman



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I did mine out of wood to use the engine as a counterweight without adding lead or other heavy material. This set-up also allows me to swap out the engine (plate and all) to the TT.40 so I can race Q.25 or 424 in a matter of minutes and keep the same CG.

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RE: .25FX Viper mount - 12/22/2007 5:38:31 AM   
Duane-RCU



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Yes Chuck, that's why I'm setting it up this way, I raced Oct/Nov with them this year. What a blast! The new one is going to be .25 only, the battery will be up front, and a few other things changed, and I'm hoping it will balance. My other Viper has the Dave Brown mount screwed to the back plate, and I can change out to the ST .45 by sliding the battery back a little. Now if I could just figure out what is a good RPM number for these FX's, and the best prop/fuel, I'll be good to go!

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RE: .25FX Viper mount - 12/22/2007 9:25:20 PM   
vicman



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8X6 APC @ 16.6K
With my set-up the only adjustment I make is to the throttle cable. Everything else stays put.


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RE: .25FX Viper mount - 12/23/2007 2:26:45 AM   
Duane-RCU



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I only wish I could get that rpm. After break-in, it was close to 16,000, then I used 15% and it went closer to 16,300 Now it's down to 15,500 on 10%, and about 15,800 on the 15%
I use the 8x6 APC. It seems to still have good compression, and when cold it will stick around TDC, so it seems to have plenty of pinch. Maybe I just got a lemon.
Thanks for the rpm figures Vicman.

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RE: .25FX Viper mount - 12/23/2007 2:54:18 PM   
Dan Vincent


 

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K&B used to make ring mounts for their old greenhead engine series back in the fifties.

I have .09, .15, and .19 rings around here someplace. They look just like the one in the first picture.

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RE: .25FX Viper mount - 12/23/2007 3:50:07 PM   
DonStegall


 

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The Hayes AL-25 Long Mount 1.19 .21-.25 is the perfect mount for the .25 engines on Quickies. The 4 bolt pattern is exactly the same as the backplate mount. Plus you can move the engine forward for balancing purposes. And at $4 is it very cost effective. I drill and tap the engine mounting holes. Some use the self=tapping screws, but I like tapped holes.

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RE: .25FX Viper mount - 12/24/2007 3:29:36 PM   
jstaff


 

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Duane do you have a gallon of fuel through your FX yet? Your numbers sound about were my numbers were, but got better with time, Mid 16's. Just keep running it. See you at the races!

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RE: .25FX Viper mount - 12/24/2007 4:13:06 PM   
fizzwater2


 

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Speed wise, how does a .25FX powered Q500 fly compared to a TTpro.40?

Just wondering, I've never seen a .25 powered quickee fly.

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RE: .25FX Viper mount - 12/24/2007 4:29:08 PM   
gunfighter


 

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Q-25 is about 100 mph, 424 is about 120 mph. + or -

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RE: .25FX Viper mount - 12/24/2007 4:33:11 PM   
vicman



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Don,
Did you need to add weight to get yours to balance? I know several others did, thats why I stuck my engine out there to get the balance without a weight penalty.

Flight wise it's a tad faster than Club 40. Not a lot...just a tad .

It looks like we are shifting to this format from SAT T-6 Texan racing this year. I like mine so far.


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RE: .25FX Viper mount - 12/24/2007 5:55:12 PM   
DonStegall


 

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Vic,

I use a 700 mAh NiMH battery in my Quickies. With the .25 FX mounted as shown, I put the battery in front of the tank in the tank compartment. I move it to the radio area when I have a TT Pro 40 on the front. It does require shifting the battery, so it is not a heat of the contest day conversion. But I don't have to add any weight. I use a JETT CG tank against the former at the front of the wing.

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RE: .25FX Viper mount - 12/24/2007 8:06:49 PM   
Electric Delta



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We used WaveOsScope to clock the Predator II and GP Viper with OS .25FX's, and the Club 40 SRM2 with the TT Pro .40BB. The Q25's were in the 91-94 mph range, and the Club 40 was in the 93-97 range, all of this measured on multiple passes. The two classes are very comparable on speed. For some reason, the Q25's look faster, even though the measurement says they are not.

On my Q25 I used a long Hayes mount, similar to what Don did, but added a Higley Heavy Hub and bolted some lead onto the mount, tucked in behind the engine. My tank is up in the front of the airplane, butted up to the firewall, and the battery on the CG, Rx at the back of the radio compartment. I have it set up so I can swap engines quickly, TT .40 vs OS .25 FX or vice versa, without the CG changing. just four bolts and the throttle linkage. I don't even need to take the wing off to do it. My Predator II ends up 2 oz lighter overall with the 25, vs. with the .40.

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RE: .25FX Viper mount - 12/24/2007 9:42:11 PM   
skull1971