Let's see how good you engine guys are

[Preston_Hall]

I am interested in chopping up an engine for a delta wing or quickie 500 plane. Yes, Jett and Nelson are already there but this is purely a play thing for me and I do not have the interest to spend the Jett and Nelson money. I also would just like to "know". I visited the Extreme Speed Prop Planes section of RCUniverse and asked the same question and the answer boiled down to either "I don't know" or "i'm not telling". Some said the engine would just blow up but we all know that is not true. And as far as they are concerned 30% nitro is to high and boat engines are not anywhere near the performance of airplane engines. I had to correct them on that. If I can go 125mph with a plane then a boat should go 150mph.

The planes are a delta wing Diamond Dust and a quickie is a quickie for the most part. Both planes are speed freaks capable of 200mph in extreme cases. At this time my quickie is doing 125mph with a Jett 40 and 8.8 x 8 APC prop turning 18,000 on the ground. I would think I could take another brand, O.S., Thunder Tiger, or Supre Tiger, and do near the same if not better. I say better because Dub Jett is obviously modifing engines for people.

So, any guess on what timing numbers would be? I guess I could tear down the Jett to get a baseline but I have not. A tuned pipe or Nelson style tuned muffler will be used.

 

[Terry Keeley]

Add a good tuned pipe, bump the exhaust to 190*, put on a 12mm carb and run 70% nitro - for starters! :lol:

 

[El Zorro]

Hey, a Quickie with a hot .40 size engine will get your attention more than a 100 MPH hydro! It's still a bunch of fun to hang onto one of those, though, isn't it? I reworked some Super Tigre X-40's back in the early 1980's for Formula 1 pylon and I have a notebook somewhere in the shop on the timing numbers. These were done when they were using the mini pipes. I don't remember exactly what the numbers were but the exhaust was probably in the low 170's. The top end for non- piped engines ( exhaust timing ) was about 165 degrees. This is where I timed my C/L Combat engines. My guess on numbers for timing would be to keep your numbers similar to the boat stuff ( exhaust in the 180's, boost and intake the usual ), just don't take the crank timing more than around 214 total..............they start spitting fuel out of the carb sometimes unless you REALLY wind them up. Remember that the engine will unload a lot more in an airplane than it will in a boat.

This is only my personal opinion from past experience. I know others will chime in on this and disagree, so please be nice about it, okay?

Glad to hear that you're still tinkering with this stuff, Preston.

**** Tyndall

 

[Preston_Hall]

****,

I haven't quit, just cut back in a big way. I definitely do not have the time to spend building and setting up boats at home and trips to the lake would be very limited as well. The price of this boat stuff these days rubs me a little wrong too. I have enjoyed the gas class since I do not have to do anything to keep the boat going. Right now I am fighting the urge to get a Seaducer cat and hardware at my door for the tune of $600. I am into the planes now because I can build the arf at home and tune it at the field in a matter of minutes. Much more relaxing. But to get the heart racing something fast must be had. Apparently it is no problem to hit around 120mph. The fastest seem to go 200mph. I would be happy with 150-175mph.

The plane guys I have talked with usually suggest bigger props. But as you and only one other have pointed out, the motor must turn the rpm so probably a smaller prop. To get the rpm you need the numbers. I was kind of thinking along your suggestions. I just needed a little reassurance.

I hope things are coming along to where you can start turning a wheel or pulling a stick.

 

[Thom]

Hey Preston. I would say that you are in the ballpark prop-wise (for the quickie). My Nelson Quickie motor (long-stroke) runs an 8.75 x 8.75NN and turns around 20,000 on the ground.

If you can tweak the timing and get a motor to act more like a Nelson Q40 motor, it's a different game. The Q40 motor (on a Q40 airframe - which is much more aerodynamic - therefore less load in the air) will usually be set up with a carbon fiber prop that is more like 7.8 x 7.5. Go find APC Props' web site and look for Quarter 40 props. These props - on a Q40 - really rev in flight. Might work the same way on your Diamond Dust.

>T

 

[Rudy Formanek]

A Diamond Dust would be a good place for some of those now cheap E-bay K&B 40 or 45's. You could start with a marine/ductedfan sleeve, air cooled head, rear drum rotor and front prop drive front end. The later model conrods (I-beam or tubular) could and would hold up to high RPM and high nitro. Rear exhaust headers can be found on E-bay or MACS Products. I would recommend MACS 8.5 cc airplane pipe, but a cheap low taper E-bay pipe would probably put just as big a smile on your face. K&B's go for so little on E-bay, you surely won't be crying too much if you explode a few. Rudy

 

[eagletwin90]

my bad

 

[bl10]

Preston:

The current crop of AMA pylon engines fall into three categories. The first and slowest is the 424 class Q500 that uses a standard Q500 (can’t have composite wing or tail) airframe with sport 40, usually Thunder Tiger Pro 40 available for around 80 bucks. Engines must be stock with exception of head shims (no sleeve shims permitted), bearings and plug. Class rules call for 9x6 APC prop and 15%. A good Thunder Tiger will turn 17200 plus. Plane speeds are slightly above 120. Don’t know what the timing is but replacing stock muffler with a Performance Specialties tuned muffler will pick up about 1K rpm. A full pipe will pick up about 1500 rpm. Muffler / pipe alone should move you into the 130 mph range.

The 2nd class is AMA 428 where everyone used Nelson, Jett or the new Profi Q500 engines. In this class a good composite engined plane will run about 165mph. We use 8.8 dia props with pitches anywhere from 8.25 to 9.25. Generally turn engines above 19k on the ground. The exhaust timing on these engines is about 168 degrees. Intake is about 126 (I think). With the high drag Q500 of DD for that matter we are not able to run any more timing because it requires a small prop, which will not pull the plane. (See below)

The 3rd class is AMA 422 (Q40), which use much slippery airframes. These things will break 200 mph on long level pass and are about 190 on the pylon course. The engines are timed about 198 exhaust and 126 (I think) boost/transfer degrees and we run a 7.4 x 8.0-5 prop. Generally we look for 25K on the ground. If you put one of these engines in a Q500 it goes slower than the same plane with a Q500 engine. Prop is just two small.

The Nelson, Jett and Profi engines are purpose built racing engines and will last forever if treated right. Even though they are 40 displacement they use a 60-size crankcase thereby permitting larger ports, bearings and a thicker sleeve.

Just a note on the Thunder Tiger. It does not hold up very well, the hard runners break cranks, bearings (if not changed), rods and pistons. I would not use it as a basis for hopping up.

Good Luck

Barry

 

[Preston_Hall]

GREAT INFORMATION!

From this I see that my Jett sport 40 does fairly well so I think I will just keep with that engine. I really can't use anything without a throttle because I can't think that fast for a tank of fuel. I paided good money for a Diamond Dust that some get to go close to 200mph but they must be doing some work to get there. Oh well.

Barry,

I guess I should check the timing on my Jett 40 or give Jett a call to see where I am. Any ideas on where to look for a used Q40? The new ones seem to be $500-$600. A kit from Stegall Hobby or Matney Models is not bad but I know there will be a fair amount of work involved. The biggest issue may be glassing the wings as I have never done this and would hate to pratice on a project like this. Does the glass need to be vaccumed or just laid?

 

[bl10]

Preston:

There have been lots of SS Nelsons, both Q500 and Q40, on EBAY. Nelson and Jett released a Long Stroke version and effectively obsoleted the old engines. They have been selling for anywhere from $150 to 250 on EBAY. Ask on the NMPRA.org web site you might get some direct help. You want to be careful when buying a used engine. I would want one from a name racer, as you probably will get a good engine that is only one version old. Nelson does not have a carb on any recent engine as far as I know but all Jett engines can be fitted with a Jett carb. (The Jett carb will not fit a nelson). I have heard there was a Super Tiger carb that Shadel (Performance Specialties) adapted but have never seen one. Perry may also offer one for a Nelson. As far a planes go the ARF Viper Q500 will hold up under the stress of any Q500 engine with minimum mods. There are threads on RCU pylon racing and NMPRA.org, which detail the mods. I would stay away from the Predator, as the wings are problematic.

Call Dub (Jett) and he can give will tell you what your Sport Jett is, what prop to run and any additional parts needed to turn it into a true Q500 engine if you so desire. Probably P/S, Head button for nelson plug and Q500 muffler.

I would guess the Sport Jett, if it’s the same one they used to run in SEMPRA (Florida racing circuit) will pull a Q500 faster than a Thunder Tiger but slower than a Q500 engine. Probably 130+

Hope This Helps

Barry

 

[Preston_Hall]

Barry,

Right now I have a Revolution Q500 with the sport Jett and it is hitting 125mph consistantly. I just need to get a Q40 airframe to go the speed I am looking for.