Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Really want to go fast??

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Old 02-19-2007, 02:41 AM
  #1  
garys
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Default Really want to go fast??

Nelson Competition Engines has released a new Q40 racing engine. As such, there are several of the current models on Ebay going for great deals. Just think what one could do in your latest speed machine...just do a search for "nelson" under Toys and Hobbies to find them.
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Old 02-19-2007, 04:57 PM
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Default RE: Really want to go fast??

Dont tell me, you have one for sale on the big E auction site!!!!!
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Old 02-19-2007, 05:03 PM
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Default RE: Really want to go fast??

http://www.rcuniverse.com/forum/m_5418326/tm.htm
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Old 02-19-2007, 06:36 PM
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Default RE: Really want to go fast??

Hey...can you put the Q500 air valve on the Q40 engine so it wouldn't have to be WFO or nuthin'?

Or isn't that how the Q500 air valve works? Doesn't it act like (or kind of like) a throttle?

I'm not talking about trying to make a Q40 Nelson idle...just knock the R.P.M. down to say 6-8,000 perhaps if you wanted / needed to throttle back a bit.

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Old 02-19-2007, 06:56 PM
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Default RE: Really want to go fast??

Yes, you can put a Nelson Quickie airvalve on it. It obviously won't idle, or transition well, but you could use it to tame it down a bit if needed.

You could also convert these motors to a Quickie motor with a new piston / sleeve / and airvalve for under $100.
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Old 02-19-2007, 08:10 PM
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Default RE: Really want to go fast??

Uh, if the Q40 flight isn't going as planned, just use a servo to pinch off the feed line. The airvalve will compromise the engines' output. If Henry saw you running a Q40 with an air valve, you would probably get black listed
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Old 02-19-2007, 08:23 PM
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Default RE: Really want to go fast??

That's what I was thinking I wouldn't want to restrict the power output...

Can't have your cake and eat it too...

I was just thinking that it would be an easily reversable change...or temporary "modification".
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Old 02-19-2007, 11:25 PM
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Default RE: Really want to go fast??


ORIGINAL: combatpigg

Uh, if the Q40 flight isn't going as planned, just use a servo to pinch off the feed line. The airvalve will compromise the engines' output. If Henry saw you running a Q40 with an air valve, you would probably get black listed

If you pinch the fuel line, restricting flow, and the air valve is still wide open...
you will soon burn the engine with a very lean run.


I just bought a Jett Q40 with BLACK carb/air valve, and will put a Jett RED twin needle carb on it. Sure I will loose 500-800 RPM off the top end. But I will have a true carburator and throttle control.
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Old 02-19-2007, 11:44 PM
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Default RE: Really want to go fast??

I think he means completely cutting off the fuel supply by means of a line pinch... not just slightly pinching it to restrict the fuel flow. And anyway, if your needle setting is correct, then even the slightest restriction in the fuel flow will most likely lead to a shut off.
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Old 02-19-2007, 11:52 PM
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Default RE: Really want to go fast??

Yep, a fuel shut off is mandatory if you want to run one of these engines responsibly. Just rig up a wire to pull the fuel line through a hole in the firewall, causing the tubing to fold in half. Rudeboy is right, it only takes a split second of fuel interruption to kill the engine
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Old 02-20-2007, 08:52 AM
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Default RE: Really want to go fast??

The quickee airvalve is 9mm, the q40 venturi is 9mm. The only thing limiting the airflow is the shape. I doubt Henry would care less if you put a $15 airvalve on one of these motors, they work fine. For sport use, I would recommend the airvalve over the line pinch method.

There is at least on q40 competitor that uses the airvalve in competition and says that there is no difference in performance. I believe he shaped the airvalve in more of a cone like shape, similar to a venturi. As long as you don't make the hole over 9mm, it is still legal in Q40.

His RCU name is DHG, you can look him up.
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Old 02-20-2007, 08:52 AM
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Default RE: Really want to go fast??

Wow, there was like 10 Nelsons on the auction site (None are mine), and quite a few top ends.
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Old 02-20-2007, 10:47 AM
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Default RE: Really want to go fast??

Thanks for that air valve info Dave...I've been thinking about a Zoomer and either a K&B 6.5, ST X40, or the ^ [8D]

I'm not concerned about taming it down...don't want to do that...just perhaps give myself a lap or so around the field at reduced power (let's say about half?) to get set-up for the approach before cutting it.

We fly from an 800' X 100' grass strip...so landing area is adequate (?) but not abundant. The approaches at both ends are clear, and open so ya don't have to worry about trees (not much anyway) but there is tall grass at each end of the runway, and I was thinking that it sure would be nice to have a lap or two around the field to get 'er slowed down some before committing to a dead stick landing.

Edit: O.K. guys...go ahead and tell me I'm putting training wheels on a Harley or sumpthing like that

The other half of me just sez "let 'er rip" WFO and go for it...but the thought of over-shooting and sailing through that tall grass at the end like a scythe (sickle?) does not appeal to me.

Like I said earlier though, it's a reversable change, so it would then theoretically be possable to get used to the engine's operating characteristics (while using the air valve ) and the airplanes handling characteristics before going to the straight venturi.
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Old 02-20-2007, 11:48 AM
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Default RE: Really want to go fast??

I would say more damage is done to q40 type planes by landing, than any other reason. They do glide quite a while and it takes a little practice in learning how far to go out before making your turn to final.

Trying to make an approach at 1/2 throttle is still going to be too much. You will be surprised at how long, even a zoomer, will glide without power after going 160 mph+.

With the availability of the Nelsons, I'd skip the K&B and the ST X40's. I doubt the Nelsons will stay above $200 in the near future.
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Old 02-20-2007, 12:10 PM
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Default RE: Really want to go fast??

Thanks Dave...
Actually, I wasn't thinking of the approach at half...just perhaps a lap around the field at reduced power to scrub off some speed before cutting it on the start of the down wind leg?

A Zoomer would zoom quite well with a Nelson wouldn't it!? [8D] Bob (High Plains) and I have been talking about it...making a good "trainer" for a Q40...(someday )
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Old 02-20-2007, 12:28 PM
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Default RE: Really want to go fast??


ORIGINAL: proptop

Hey...can you put the Q500 air valve on the Q40 engine so it wouldn't have to be WFO or nuthin'?

Or isn't that how the Q500 air valve works? Doesn't it act like (or kind of like) a throttle?

I'm not talking about trying to make a Q40 Nelson idle...just knock the R.P.M. down to say 6-8,000 perhaps if you wanted / needed to throttle back a bit.

Dub actually sells some of the "practice" QM40 and FAI engines with a fully functional carb. Its not going to idle at 2000 rpm (more like 5000), but it gives pretty good throttle control

A few years back, a bunch of us actually prefered using the airvalve on the QM40 engines - gave that 'enriching' capability on the start line, and also allow for flood-off at the end of the flight. RPM drop is negligable with respect to sport/speed use... maybe 1000 total (since it is a smaller bore than the QM40 venturi).

Bob
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Old 02-20-2007, 01:39 PM
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Default RE: Really want to go fast??

Those engines on ebay are starting at $170. Isn't that kind of ridiculous for used engines that are being dumped?
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Old 02-20-2007, 02:02 PM
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Default RE: Really want to go fast??

Nope, just spoke with Henry and he assured me that any Revvers caught running an air valve will be ex-communicated. Also, the 9 mm venturi is restrictive, the engine will handle 11 mm with ease.
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Old 02-20-2007, 03:15 PM
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Default RE: Really want to go fast??

The 11mm venturis are typically used at high elevation (Mexico City) or Overseas where Nitro is not used.

$170 is a very fair price for a $400 engine in my opinion. Most of the motors listed have very little time on them, but I would definately watch what you are buying, as that may not always be the case. Just because they are roughly 2% off the newer version, doesn't mean they aren't stump pullers.
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Old 02-20-2007, 04:10 PM
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Default RE: Really want to go fast??

[8D] Bob and Dave...thanks

Hey Chuck...telling a non-conformist that he would be ex-communicated is like waving a red flag in front of a bull...

Besides...it ain't like one would be doing an irreversable change to anything. It would be more like half a dozen flights or so, to get used to the airplane, engines, etc.

Would you like to land a Q40 on an 800' grass strip? Don't think it'd be easy...but do-able (?)
I have a feeling that if you didn't get your approach just riiight, it would be real easy to over-shoot.

Don't forget, we're not talking (at least I'm not ) about any kind of actual racing, or rule book, etc. so it would just be flying a fast airplane, with a bit of a "peace of mind" factor or option when it comes time to think about landing.

(CP, you kind of make it sound like I wanna draw a mustache on the Mona Lisa )
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Old 02-20-2007, 05:34 PM
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Default RE: Really want to go fast??


ORIGINAL: Kmot

Those engines on ebay are starting at $170. Isn't that kind of ridiculous for used engines that are being dumped?
Nelson engines are about 400.00 new so at less than 50% of new for a motor with 20 or 40 runs is not bad.

There are two different sellers each with several engines on that auction site BOTH with ZERO on feedback. Zero feedback to me is a big red flag.

I do not know either one of them so I cannot comment on thier engines.

In a phone conversation with Dub Jett somebody possibly in Florida was selling used Jett engines on Ebarf. The condition of those "used" engines was less than stated...more like battle tested/ready for rebuild.
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Old 02-20-2007, 06:10 PM
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Default RE: Really want to go fast??


ORIGINAL: daven

There is at least one q40 competitor that uses the airvalve in competition and says that there is no difference in performance. I believe he shaped the airvalve in more of a cone like shape, similar to a venturi. As long as you don't make the hole over 9mm, it is still legal in Q40.

His RCU name is DHG, you can look him up.
Yep, it works great. The "idle" is actually a very rich half-throttle setting, but it will come back up. That's handy for flight trimming, or keeping the engine cool on the runway before launch ... or let's say you're racing at the Nats and your caller tells you "up & out" because you've double-cut, but then he realizes he was watching the wrong light and you dive back in to grab a 2nd place instead of a zero. That's sweet.

I think I know who those two sellers on ebay right now are, and if it's who I'm thinking of, you have nothing to worry about. $170 is a steal. Imagine if you looked through the local want ads and found a nearly new Ferrari for $2,000. Yes, you could buy two used Ford Mavericks for the same price, but why?
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Old 02-20-2007, 06:26 PM
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Default RE: Really want to go fast??

The three sellers on there are all very well known in the pylon world, not that that means anything, but I wouldn't hesitate buying anything from them. They are obviously upgrading their equptment.

The user "snoogi" or something like that is the wife of a 6 time National Champion, and his engines are very well taken care of and serviced by Dave Shadel.

I know I would have absolutely no hesitations in buying from any of them.

I'm keeping my 3 paper weights for practice
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Old 02-20-2007, 07:16 PM
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Default RE: Really want to go fast??

Proptop wrote

Would you like to land a Q40 on an 800' grass strip? Don't think it'd be easy...but do-able (?)
800' is very do-able. Do not be intimidated by top speed numbers. The grass field I practice on is 500' long. In the summer I have to come in over corn, I have not overshot yet. I lose height with a couple of circles and then run straight in. A Q40 will slow down to a comfortable landing speed.

I have to practice by myself. Launching from grass can be a bit of an adventure but one gets the hang of it. I have to get up and away quickly to miss the bushes. See picture.

Coming in over the corn can be fun as well. See picture.

Ed S

P.S. I did not take the pictures!!

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Old 02-20-2007, 08:04 PM
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Default RE: Really want to go fast??

More left aileron Ed.

Q40's are very easy to land. Just slow down at altitude then glide down at constant speed. Do you understand the "J" curve, and flying on the backside?
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