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Jim Allen

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About Jim Allen

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    National Racer
  • Birthday 01/30/1941

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    Graham, NC

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  1. Good job guys. Looks like all the photos & posts are back up. JA
  2. Jim Allen

    Worn out P/S?

    Bob, In the very early days of ABC & AAC engine building, a tight fit between the piston & sleeve, plus a course crosshatch honing pattern was used to compensate for the "out of round" (+ or - .0002") condition of the piston & sleeve. A roundness (+ or - .00005") of both parts is absolutely essential before anything works properly! We eventually discovered that the tight fit method does not correct "out of round" problems & it does not extend high RPM engine life! Some engine builders thought that higher amounts of silicon in aluminum alloys used for pistons would prevent piston scuffing or engine seizing. This is also untrue, as the answer to this problem involves the cylinder taper amount & the piston top taper amount. You are correct about what cold fit can & should be used with the many possible piston, cylinder alloy combinations that can be used. We have tested & used in production miniature racing engines the following piston alloys; A-390, Dispal 250, Mahle-138, RSA-431-T6 & RSA-444-T6. We have tested & used in production racing engines the following cylinder alloys; C 36000 brass, C 54400 phosphor bronze & 4032-T6 aluminum. All of these alloys require different cold fits! However, Nothing works properly until the involved parts, the piston & the sleeve, are properly machined & finished! The correct mechanical design of these parts is also absolutely necessary! Jim Allen
  3. Jim Allen

    Are radar guns accurate for boat speed?

    Stephen, I use a Stalker PRO radar gun. To get the most accurate reading possible the radar gun must be placed directly in line from the front or rear of the boat. We use a dedicated person stationed at the end of the lake with a TRC-236 transceiver which allows communication as each pass is made. Standing on the shore always produces a tangent error that is hard to calculate! We have also used this gun to check radar speed readings when compared to data logger speeds derived from a pylon racing plane. As long as the radar gun is in line with the object being tested, it will read correctly! The gun comes with a tuning fork for onsite calibration. Jim Allen
  4. Jim Allen

    Worn out P/S?

    "What are the symptoms of a worn out piston/sleeve? I have a 21 Nova DD with absolutely no pinch left at the top." Bob, A loose fitting ABC or AAC piston & sleeve, in a tuned piped engine, doesn't necessarily mean the engine in question is worn out! ABC or AAC tuned pipe engines can still run strong even when the piston has lost most of its "pinch" at the top of the stroke. It is a proven fact that a looser fitting ABC or AAC tuned pipe engine will run faster, but will not produce high torque amounts at low & mid-range RPM's. The lower torque amounts can easily be seen when attempting to pipe up a looser fitting engine that is under load. A much more important factor for ABC or AAC tuned piped engines is how round the piston, sleeve (within .0001" works best) combination are, as well as how round they remain at WOT temperatures & RPM's. Sound mechanical design of the piston, sleeve combination make this possible! Jim Allen
  5. Jim Allen

    new gas pipes under construction

    This information comes from Les Smith of Performance Unlimited. It speaks about the progress of the 32 cc to 35 cc Pipe R&D work. This tuned pipe's design follows from the research developed over the last year. "The R&D design and the testing of our new Stainless Steel Pipe is finally being finished....below is a synopsis of the R&D testing ... The final results are more than impressive to say the least. Ray's 20 lb 53'' Delta Force Annihilator Mono started out with a top speed of 51 mph with a modified 30.5 cc engine using a QD Hot Pipe. He upgraded the displacement to a 35 cc engine and tried the following pipes from QD, Insane and Zipp Kits with no better performance than the 30.5 cc using a QD Hot Pipe, the JB pipe gave a little improvement over the others and all running in the 17k-18,600 rpms, however...the Pro-Modified 35 cc engine was producing the same power as the 30.5 cc, since the same prop was turning the same rpm as the 30.5 cc and the 35 cc was also showing a lot of increasing engine heat from the CHT sensor readings were going above 205° and then the performance of the engine was sluggish and the top end power dropped off. We went through 7 different designs of the pipe as well as several different shapes, angles to mention a few and the performance of the 35 cc engine came alive and we kept testing in the direction of the performance increases and the CHT temps were monitored closely to insure no melt down will occur at WOT for an extended period of time that was way beyond any heat racing or marathon running time frame. The air temps in the 3 digits and altitude changes from sea level to Las Vegas did not hinder the performance gains with the new pipe. Rays heavy mono now has a speed of 65.6 turning a prop with more pitch and rpms around 20k-21,400 with no over-heating and plenty of bottom end to more the heavy hull. This pipe is not a spin off of a QD Pipe, Zipp Kits Pipe, Insane Pipe or a modified pipe from those on ebay as some have done to sell pipes by modifying them and claim this is the pipe for the 32-35 cc or to claim their pipe works on this size of engine. In the R/C hobby most pipes will work across several different engine displacements, however only a pipe that is specifically designed for the engine and its displacement will work even better. There are several guys that have been there when Ray first started the testing and have witnessed the performance improvements during the R&D testing and have visually seen the results of the pipes performance even during NAMBA District 9 races. We are pursuing to have this 4 stage pipe stamped out of Stainless Steel and we decided on this method, since the inside of the pipe is smoother than a bunch of welded stages and the angles are radius to the other areas along the pipes length, so the pipe will have the welds similar to a QD Hot Pipe and have the flared diffuser that you can see without the welded stages and of course be lighter in weight too. The 32-35 cc Pipe uses a 1" header All clamps are Stainless Steel Muffler on our pipe has an integral stinger Weight of the pipe with stinger & muffler is 17 ozs JB Pipe is 18.8 ozs and QD is 15.4 ozs Below are photos of the visual differences between the tuned length and / or the pipes shape and length of the QD, JB and our pipe. Top Pipe is Our Stainless Steel Pipe, Middle Pipe is a JB Pipe and the Bottom Pipe is a QD Hot Pipe."
  6. Jim Allen

    Glow plug torque specs?

    Hi John, I use 1/4" drive, 0 to 60 in/lb, Armstrong beam type torque wrenches for tightening plugs & head bolts. Standard 1/4-32 plug threads are tightened to 45 in/lbs & 11/32-32 tapered seat plugs are tightened to 48 in/lbs. #8 SHCS head bolts are tightened to 20 in/lbs & #4 SHCS are tightened to 10 in/lbs. No loosening or thread stripping problems of any kind found thus far. Jim Allen
  7. Jim Allen

    Charlotte, NC area?

    Thanks Much Don! JA
  8. Jim Allen

    Exhaust Gas Pressure inside Tuned Pipe?

    Okay Mike, Let us know what you find out. Keep in mind that any tuned pipe or magic muffler type device that has insufficient volume compared to the engine's displacement will "NOT" allow large changes to a stingers ID or length. JA
  9. Jim Allen

    Exhaust Gas Pressure inside Tuned Pipe?

    Mike, I haven't measured the pressure in a tuned pipe or magic muffler type pipe of a .21 cuin size engine. However, I have measured the pressure in various types of magic mufflers & tuned pipes used on .40 cuin to 2.0 cuin racing two stroke engines. The measured pressure always varies directly with the engines RPM. In this respect it is different from crankcase pressure which remains almost constant over the engines operating RPM range. Measuring the pressure, at various points in piped systems of either type, has very little effect on the amount measured. I use a zero to 200 inches of water type gage to measure pressures from 2.9 to 3.9 psi at WOT. The reason that a water gage is used is to enable accurate readings of the small amounts & differences in pressure readings that are possible. For example, 2.9 psi = 80 inches of water & 3.9 psi = 110 inches of water. The gage in the photo measures 100 inches of water at its midpoint. I'm presently using tuned pipe pressure with large bore diaphragm type carburetors. This pressurized fuel system works extremely well over the engines operating range. Jim Allen
  10. Jim Allen

    Charlotte, NC area?

    Do you have any more information concerning address or who to contact? JA
  11. Jim Allen

    new gas pipes under construction

    Rudy, We presently have a functioning chamber that will be tested further on the water. The Performance Unlimited 35 cc engine has the necessary timing numbers, raised compression & tuned pipe design to move the peak HP point from 18,500 to 20,100. Doing this allows the same 20 lb Delta Force mono, with the same 7016 3 blade 395 propeller to increase its speed to 65 MPH. The boats speed, engine RPM & engine temperature at WOT are being measured real time. Further testing will be done in an attempt to raise the peak HP, at the same RPM number, but keep the engines operating temperature at WOT below 200* F. This will be attempted with a small reduction in the pipes total volume from 1010 cc to 952 cc. Jim Allen
  12. Jim Allen

    new gas pipes under construction

    Definite progress is being made on a suitable tuned pipe for 32 to 35 cc engines. These chambers should be ready for sale in October or November of 2018, through Performance Unlimited. We have found that a 7/8" header causes high heat problems at WOT. This happens even when the chamber has an adequate volume, an adequate stinger ID & length, an adequate cooling system & a tapered header. Therefore, only a 1.000" header will be used on the 32 to35 cc size engines. The 7/8" header is still used on the 26 to 28 cc engines without any WOT high heat problems. Jim Allen
  13. Jim Allen

    Testing for a possible new World Record today

    I met Ken Warby when he visited Huntington, Long Island many years ago. I remember the video of the original boat hitting a bird during one of the speed runs. I also remember the video of how the boat moves from side to side which was taken from the rear during a speed run. Good luck to a gentleman & a very knowledgeable engineer. Jim Allen
  14. Jim Allen

    Spreading the word

    Good heads up Grayson. At Aero Precision Machine, Inc. located in Liberty, NC we build the Nelson Q-40 & Q-500 pylon racing engines. Also, one of the best flying fields in the USA is located in Liberty. The field has a paved runway 500 ft long X 75 ft wide & is level within 5/8" from end to end. A three pylon measured course is permanently set up & electronic timing is used for the world class events held there. It would be a shame to lose a flying site such as this. Jim Allen
  15. Jim Allen

    Charlotte, NC area?

    This is a satellite view of the running site at Falls Lake State Recreation Area located at the end of Baptist Road. There is no swimming allowed, but this is not enforced because there are so many people breaking the posted rule. Therefore, during the summer months, we run on Mondays & Tuesdays only. Once the water temperature drops the other days in the week are available. The launch area is 500+ ft long & you can walk out into the water 80+ ft, with the water depth still at 3+ ft. Notice the paved parking area & the short distance to the water's edge. The useable straight away is 7,500+ ft long with the back side of the running site 5,600+ ft away. Note: A good gas powered retrieving boat is allowed & required on a running site of this size!! Jim Allen