Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 94758 times)

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #420 on: September 12, 2019, 04:23:36 PM »
With lower performance engines running pumper carbs, an IV bag works fine.  However, we had lots of problems getting a modified Walbro WYK carb to pump enough fuel in an engine like Jim's.  Lower pop off pressure and a Perry pump got us by.  Pipe pressure systems on nitro engines act like a simple throttle body fuel injector.  As the power goes up, the pipe pressure increases, increasing the fuel flow.  The double tank system helps maintain a consistent fuel flow at the carb like Jim explained.   

Jim, are you running a pumper carb?  Does the pressure regulator still handle the increased pressure and meter fuel well?

Lohring Miller

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #421 on: September 12, 2019, 05:48:23 PM »
Petertha,

Sorry about the confusion caused when I used the word "bladder". I was not referring to the rubber bladder type fuel systems used in the  past on some speed planes. I was referring to the hospital type IV bags adapted by many model boaters to replace metal or blow molded seamless type tanks. The blow molded, heavy duty type, tanks can be used for continuous pressurized fuel systems above 5 psi. The engine RPM's, tuned pipe total volumes, stinger ID's & lengths are some key factors that will determine how much pressure can be developed at any throttle setting. I am running a pumper type carb with the tuned pipe pressure. The maximum measured pressures generated with my tuned pipe designs are approximately 4 psi (110 ounces of water) at WOT.

Lohring,

Extensive dyno testing of my gas engines operating at RPM's above 21,000, with an "adequate" tuned pipe pressure, showed me that no change was necessary to the pop off pressure. In fact the tuned pipe pressurized system works in a similar manner on both gas & nitro engines, providing the tuned pipes design is "CORRECT". I can assure you that tuned pipe volumes that are to small combined with stinger diameters that are to short & to large WILL NOT WORK!!

Note: Present day pylon racing planes also use the pressure generated from a tuned muffler to provide an adequate fuel flow at RPM's of approximately 30,000. The measured pressure for a .45 cu in engine is approximately 90 inches of water at WOT.

Jim Allen
« Last Edit: September 12, 2019, 07:13:47 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #422 on: September 17, 2019, 04:19:57 AM »
3" OD pool noodles are used for flotation after their ends were sealed with Goop. I used Nokorode Black Silver Soldering Flux & Aufhauser Silver Alloy 45 (1370* F - 1550* F) for the tuned pipe pressure fittings, any tuned pipe joints & 1/8" of the cable's end that goes into the collet. The aluminum heat sink fixture prevents any heat from traveling past its end point. Silver soldering the cables end eliminates uwinding problems. This same heat sink will be clamped approximately 1.250" from the cables end. Lucas-Milhaupt 400* F solder with Lucas-Milhaupt Tec Flux is used to make the entire 1.250" end of the cable a solid.

Jim Allen

Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #423 on: September 20, 2019, 12:01:33 PM »
Going back to the Piano wire drive shaft: As your engine appears to reach higher rpms that the one you are basing your design on have you considered the need to move the support bearings closer together to reduce the risk of whirling?
Best regards

Roger

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #424 on: September 20, 2019, 03:52:24 PM »
I would be interested in a comparison between the cable versus the wire drive.  It looks like you are planning to be able to run both.

Lohring Miller

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #425 on: September 20, 2019, 07:17:12 PM »
Roger & Lohring,

There are many unsubstantiated & unproven claims about the advantages of wire type drives. Claims of a 5 MPH increase in the maximum speed of a boat may be very possible because of the inherent drag of a "longer length", 1/4" OD, flexible, cable type system. The original purpose of using a wire drive was to allow the propeller's strut to be adjusted in depth & angle. As boats became larger & longer, wire type drives were replaced with solid shaft (3/16" OD) drives with ball & pin universals. Kalfus developed precision, very high quality, ball (.2812" OD) & pin (.1250" OD) type universals which I adapted to .65 cu in engines. Next came solid shaft (1/4" OD) drives with ball (.3125" OD) & pin (.1562" OD) type universals which I use for the .90 cu in geared twin setups. All of the solid shaft setups have very low friction amounts. There is no "shaft whirling or sine wave" activity to be concerned about if the shafts used are straight & they are "moderately supported". This is true at tested RPM's of 30,000+! Keep in mind that very few people have the expertise, knowledge or equipment to manufacture what would be necessary to build even a simple system!!

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #426 on: December 08, 2019, 11:43:41 PM »
This will be my last post until things are set in the new shop in Suffolk, VA. The last thing done for the 19 HE carburetors was to machine some custom needle valve clamping devices.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #427 on: February 07, 2020, 09:46:53 PM »
Hi Guys,

I'm in the process of getting the shop set up in Suffolk, Va. Many valuable items such as various materials, fixtures, jigs & boat hulls had to be thrown out because the shop had to be downsized & I was unable to sell or give the stuff away. I gave away a new retrieving boat, new motor & new trailer to the real estate agent. It cost $3,500.00 to move the shop equipment 214 miles. Another $5,500.00 for the mini-split & $3000.00 for lights & electric. Now that the move is completed, I wonder if model boating will be in my future.

Jim allen

Offline Jo

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #428 on: February 08, 2020, 08:10:59 AM »
I hate having to move a workshop: I did it once and will not do it again  :hellno: The worst is now over Jim, hopefully it will seem like home again then you can look to find a new boating lake to play on  :)

Jo
Enjoyment is more important than achievement.

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #429 on: February 12, 2020, 03:01:37 AM »
Hopefully you will feel settled in soon, Jim & we can see some more of your marvelous works again. Moves are no fun at the best of time & metalworking machinery add extra challenge.

Offline Ramon

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #430 on: February 12, 2020, 09:00:34 AM »
Jim - I can empathise with the situation so here's to you getting set back up and 'firing on all six' before too long. Finance aside it's never easy breaking down something that's become so familiar and having to rebuild it. Looking at those superb examples in those images however I very much hope that model boating still finds a place for you.

Good luck for the future however it may pan out :ThumbsUp: :ThumbsUp:

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #431 on: February 13, 2020, 09:46:10 PM »

Rm .oo5 ohms
Kv 824
Io 3.27 amps @22.5 volts including radial fan load.
Weight 448.8 grams

Here it is on 12s in the FE boat cal.

ABC 1818 calculated as most efficient prop in its database for performance hydro @ 12s lipo 9800 mah

33,940 rpm
153 amps
Pin 6.394 kilowatts
Pout 6.125 kilowatts
Run time 3.85 minutes
Est speed 90.12 mph or 145.03408 km/h
Eff. 95.80 %
Hi James,
Glad to know you are still here. Any good racing in suffolk? Are you rubbing shoulders with Ferrette? Im going to take his scale record soon enuf. Have you seen my new APD drive? It the most power dense esc on the market and it cost like a quick draw.  Is your email working I have a lot of  wonderful things to show you . This is an old motor. You could use this and some large load resistors and have a very nice brake for the nitro and gas engines. This was old this is where im at now. Winds that remove ripple and unwanted harmonics. I have well over 20 Kw of braking resistance. This is fully variable with fets and duty cycle.

 

TTYL
Hubert
« Last Edit: February 13, 2020, 09:56:12 PM by DRT »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #432 on: February 13, 2020, 09:52:53 PM »
These motors have a preece value of over 400 amperes. The Onderdonk rating is ridiculous.


« Last Edit: February 13, 2020, 10:03:33 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #433 on: February 14, 2020, 06:16:42 PM »
Looks like you have continued with your work Hugh. Keep up the effort, it will pay off one day! I haven't made contact with any one as yet because I'm setting up the new house & shop. There are still many things to be done.

JA

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #434 on: February 17, 2020, 09:15:26 PM »
Thanks,
I see you are still perfecting the craft. Let me see the hardware u created for the boat. Rudder strut etc. And how are you securing the wire drives to the motors. Some of the Guys in Germany are actually modifying mill collets. Please excuse me if you posted this already and I just haven't seen it. With the job and projects its difficult to track threads daily though I try. The cat looks really good btw.