Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 88105 times)

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #360 on: March 06, 2019, 11:16:45 PM »
Good Guess, but no cigar. There is a part I failed to show which is used to lock up the drive shaft for tightening the 5/16-24 propeller lock nut.

JA
« Last Edit: March 06, 2019, 11:31:40 PM by strictlybusiness1 »

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #361 on: March 07, 2019, 11:17:16 AM »
Drilling holes in order to lock the wristpin …?... but wouldn't that weaken it ?

Smart feature, as it will be used every time you need a different prop as load  :ThumbsUp:
« Last Edit: March 07, 2019, 11:21:08 AM by Admiral_dk »

Offline Niels Abildgaard

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #362 on: March 07, 2019, 08:04:37 PM »
The simple fixture shown allows the stock piston bosses to be re-machined to a particular dimension & square to the stock wrist pin axis. What could be the reason that this is being done?

Jim Allen

To put piston on a stub in lathe for turning piston top to suit  some far fetched torodial cylinder head

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #363 on: March 07, 2019, 09:14:04 PM »
Drilling holes in order to lock the wristpin …?... but wouldn't that weaken it ?

Smart feature, as it will be used every time you need a different prop as load  :ThumbsUp:

No. Wrist pins are a press fit in the piston bosses.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #364 on: March 07, 2019, 09:22:07 PM »
The simple fixture shown allows the stock piston bosses to be re-machined to a particular dimension & square to the stock wrist pin axis. What could be the reason that this is being done?

Jim Allen

To put piston on a stub in lathe for turning piston top to suit  some far fetched torodial cylinder head

No. Pistons are mounted on an internal expanding collet for final machining. The wrist pin hole & a snug fitting gage pin are used to ensure the piston's OD is square to the wrist pin hole.

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #365 on: March 08, 2019, 02:12:57 PM »
Are you shimming between the small end and piston to align the rod between the crankwebs?

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #366 on: March 08, 2019, 04:07:56 PM »
Correct Dieselpilot!

I will set the total clearance in the upper end at .003" to .005". The total clearance in the bottom end is set at .010" to .015" which means the connecting rod is being guided between the piston bosses. The reason that this works so well is because the rotational speeds in the upper end are much lower than the rotational speeds in the bottom end. I also set the total axial movement of the crankshaft at .004" to .008". There is much more to this procedure that will be explained later.

Jim Allen
« Last Edit: March 22, 2019, 08:46:48 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #367 on: March 22, 2019, 08:45:24 PM »
This is a custom designed rudder system that allows the rudder actuation to be pulled for right rudder. Standard systems will push the actuation rod for right rudder. All the parts are made of full hard AISI O-1 tool steel. Machined teflon washers & rub plates are used at high wear points. The total movement, right to left, is very smooth & positive with very little friction.

Jim Allen
« Last Edit: March 22, 2019, 08:50:20 PM by strictlybusiness1 »

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #368 on: March 22, 2019, 10:02:41 PM »
The rudder system looks fantastic, but I must admit that I have no clue as to why reversing the movement is such an improvement ....  anything to do with prop rotation  :noidea:

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #369 on: March 23, 2019, 03:23:07 PM »
A pull linkage doesn't need to be stiff for accurate rudder positioning.  Since we race clockwise, the boats are making right turns.  Water loads are much higher than most people realize.  Think about sticking your hand in the water in a boat going 20 mph versus sticking it out a car window at the same speed.

Lohring Miller

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #370 on: March 24, 2019, 12:25:35 AM »
Thank you for the explanation Lohring  :cheers:  makes sense.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #371 on: March 26, 2019, 04:25:23 PM »
I also want to thank Lohring for explaining why this type of mechanism can be used in place of a rod that is pushed for right rudder movements. I must apologize for leaving things unanswered, but I have a large, time consuming, workload. Two other projects that I'm presently working on are shown in the posted photographs. The two 1.500" thick aluminum blocks are the base pieces used to make a die set that will be used to assemble & disassemble three piece crankshafts. Four .500"  OD X 4.500" long dowel pins are pressed into the reamed base holes of .499" ID. These same 4 dowel pins become a slip fit in the movable top piece which has holes reamed at .501". It is very easy making something such as this when the milling machine has been properly trammed. All four holes are drilled & reamed without moving the pre-machined "squared" blocks.

The last photos show how I use a sine vise, with gage blocks, to set up a rudder milling & drilling fixture at an angle. A Sperry AngleStar Digital Protractor is used to check the setting of the angle. This fixture will be used to mill wedge shaped rudder blades.

Jim Allen


Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #372 on: April 03, 2019, 03:51:01 AM »
Sorry for the delay You could use a SA, PA, or RTA, and they have those apps on the phones, but I see no particular better reason to record the pipes wave and analyze that way unless you just want to use that method. This was Lohrings method taking point forming a line. Which mathematically I see nothing wrong with. My point is him finding the most accurate line fitting within the method in which he recorded the data. That was the way. This FFT analysis may be a suggestion he could do something with.  I never hear any discussion about 1/4λ or 1/2λ sublimation or constructive interference versus destructive. If a pipe boost similar to a pipe organ I'd expect to see more discussion from that side of things when it comes to a TUNED pipe but I don't want delve deeply here into that discussion only opening a can of worms sourcing my 30 years sound engineering experience. I'll leave that alone here. The only time I even heard the terms use by motor builders was when Jim was telling me about Henry Nelsons magic muffler. So from here it appears Henry was the only one that considered the phenomenon in sound waves with his plane motors.

Don't worry I'm very familiar with recording FFT when analyzing the harmonic content of the electric motors and power systems. I'm a robotics technician for Mercedes Benz.

I'm building a permanent magnet flux switching machine that will produce 25mN from a standstill to nearly no load speeds. @ 2.7kW that's pretty damn good. This design was taken from downhole pump applications. You see the outer rotor has no magnets. The pieces are in the arms of the stator. The motor is only 50 mm in diameter. The motor is also good because it is mostly steel and can give really good performance even with inexpensive steel versus a lot of  expensive rare earth or copper in a high quality conventional pmbldc used for rc models . 

 

« Last Edit: April 03, 2019, 01:01:01 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #373 on: April 03, 2019, 05:57:25 PM »
Looks like we both have many things going on at the same time Hugh.

I will return to working on the special 1/4", full wedge, 7075-T651 aluminum rudder blades that have a 5/32" water inlet hole. The ID of the entire H2O water line is 5/32" ID without any restrictions up to the engine. This will be the largest water inlet hole ever to be used in a blade of this thickness which has a tapered  back edge towards the bottom. At the point where the side blade H2O inlet is placed the rudder will be .215" thick. This means that both drilled holes must be on center which will give a .0295"/side wall thickness at this point. I use a precision angle block to hold the rudder blank square in two axes for drilling the back edge water  hole. Another fixture, to be shown latter, will hold the rudder blank for the side water hole drilling operation. The same fixture will be used for cutting the rudder's final wedge shape. The water line barbed fitting is a machined brass piece that is pressed into a .2031" ID bored hole.

Jim Allen

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #374 on: April 03, 2019, 08:41:50 PM »
Hi James,

Buzy but can always handle more.....The rudders are beautiful and I want one so send me all the prints for the pieces and lets see how far the "puppy" has come.
 
We're never on any ones time table but G's and he punches the real clocks.... Im going to send you plans for a eddy current dyno similar to the one Lohring started from the University paper I sent you a while back with the hard drive platters with all the acquisition equipment that can handle the speed of you motors. It will be steady state. Realize with the right setup the motor doesn't even have to be hard coupled to the brake. You've seen nothing yet wait till I shake up things injecting ferrofluid in the air gap of my motors for much better cooling and completion of the flux path across the gap. It need no pump James. Because of it curie properties cold fluid displaces the hot fluid that not isn't as magnetic as the cold.  Look up Steve Papell's work at Nasa. he designed it for passive fuel delivery in a rocket engine.

@ Lohring do not share my electric ideas with the electric boaters at OSE or IW they know it all already and I do not want to help any of them at all. You know I'm happy to share them with you if you are interested. In time all of them will see it in Elizabeth City! When I come to claim all my IMPBA jacket speed patches at one time! I'm coming believe me.

Whatever you do, work at it with all your heart, as working for the LORD, not for human masters....
Colossians 3:23 23
« Last Edit: April 03, 2019, 09:21:09 PM by DRT »