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...

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

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.

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!

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

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.

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.

The [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXK805&P=7]Hayes AL-25 Long Mount 1.19 .21-.25[/link] 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.

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!

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.

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

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.

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.

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.

Delta, which was faster the PredII or the Viper with the 25fx??

Chuck and or Duane can ya'll point us in a direction as far as race dates, locations, and rules. I'm from the DFW area and it'd be fun to "Go home" and play.

So far, with the battery in the tank area, it looks like the balance will be ok. I'm not quite finished. I thought having the shorter nose was a better thing, that's why I mounted it like this. Plus the firmer an engine is mounted, the better for rpm. This is just stuff I've heard, no data to back it up. As Electric Delta pointed out, our speeds seem close, we clocked my other one at around 90, Joe's was faster, I think 95-96?
I'd like to know more about the Pred II also, like tank area, and how hard the rear linkage is to do.
Skull, here is a couple of links... There are two that do this so far, Benbrook, and Tx Wings.. http://www.fwthunderbirds.org/ http://www.txwings.com/
Rules are there too. About 15 pilots are showing up, and this is getting better!

Thanks Duane, I have a Pred I with a Rossi 40 on it, flies on rails and it's just a bit faster that a TT40, (A small bit). I've heard that the Pred II is not as good, I DON"T KNOW, would someone please chime in on that. I also fly Vipers, and they are a handfull till you learn the tricks and get the trim right.

I've flown both the Pred II and the Viper with the TT Pro 40 and there seemed to be little difference in speed. I did not fly any heats nor put it on a radar gun. Just casual observation.
I feel the Pred II is easier to set up than the Viper and I really like the internal linkages.
I have a Pred II with the OS 25 I am just about to maiden. Will let you know how it does after the first race at Thunderbirds.
As soon as I hear from a couple more clubs, I will post a schedule for sport racing for all of Texas. At this point it looks like we will have in excess of 40 races between D/FW, San antonio and Houston. This includes Q-25, Club 40 and 2 pole 424.
If any of you are planning races at your club this year, PLEASE send me an e-mail so I can get your group on the schedule!
[email protected]
Chuck

With the OS .25FX's, there was no discernible difference in speed between the Predator II and the Viper. I've only owned and extensively flown the P-II, but have flown a few other folks' Vipers as well. My personal experience was that the P-II flies and handles steadier, and that the Vipers all tended to hunt around on elevator some. That may be due in part to set-up, and personal preference, the quality of the ruddervator servos, etc. so take these comments with a grain of salt. I haven't yet had the opportunity to set-up a Viper of my own, but it's definitely still on my list of planes I want to put in my hangar.

Regarding the enclosed ruddervator linkages on the P-II, this was pretty easy to do and works well. Absolutely no complaints. Also the tail incidence on the P-II was right-on, out of the box; I have heard the Viper tail needs to be shimmed to get the incidence right.

Not much to say about the tank area on the P-II. The space is adequate, as long as you plan on a rectangular tank, 6 oz or less. I am using the Tettra bubbleless tanks, the 4 oz the 5-1/4 oz or the 6 oz will all fit fine, not sure about the new 5-1/2 oz "fat tank". The front end could be sturdier. I believe the P-II has been lightened up vs the P-I, and that this was a mistake up front. I would recommend a little beef-up in the tank area, add 1/4" triangle stock in all the corners and glue the hatch on permanently, rather than screwing it on (you can install or remove the tank from the rear). This will strengthen and stiffen up the front end, without adding too much weight. Maybe not really necessary for Q25, but you might as well, since otherwise the plane will most likely end up tail-heavy with just a .25 up front anyway, and if you anticipate putting a .40 on it, the extra strength will be welcome.