Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129370 times)

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #150 on: April 05, 2015, 09:32:33 PM »
I'm still very impressed and grateful for your explanations - it's nice to see that I'm still able to learn something about two-strokes and more about how to make them  :cartwheel:

Best wishes

Per

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #151 on: April 05, 2015, 10:38:26 PM »
90LX_Notch & Admiral_dk,

Building mechanically reliable, very high RPM, very high HP, two cycle engines has very little to do with what most people are trying to do to these things. The ability to machine designed tolerances to exacting numbers always tells the designing engineer which number is working & which number is not working. NUMBERS, NUMBERS & more NUMBERS applied to such things as axial, radial, roundness, squareness, tensile, yield, ductility, metallurgy, etc., etc., allow the design engineer who is capable of making the "number", to find solutions to problems. I am quite sure you both understand exactly what is being said here.

Jim Allen
« Last Edit: April 05, 2015, 11:48:16 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #152 on: May 10, 2015, 07:40:45 PM »
I'm in the process of relocating. I haven't had time for the engine building stuff except for the latest connecting rod project. The new rods are a replacement for the failing Zenoah 320 connecting rods. The other  photos are what should not be done & the results of a very poor design.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #153 on: May 11, 2015, 08:00:43 PM »
The machined connecting rods shown in the photo are a direct replacement for stock connecting rods that fail at sustained RPM's of 16,000. Incorrect design, tolerances, metallurgy & heat treatment can prevent the building of any high performance connecting rod.

Jim Allen

Offline 90LX_Notch

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #154 on: May 12, 2015, 01:24:28 AM »
Thanks for the update Jim.  I'm still following along with great interest.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #155 on: June 29, 2015, 12:16:50 AM »
Heavy heat treating fixtures will be used, with the rods clamped in between, to prevent any bending or twisting of the machined connecting rods during hardening. The rods & their fixtures will be sealed in air tight .002" thick stainless steel bags to prevent any decarburization during the through hardening process. The Sen/Pak System of heat treating utilizes a metal foil container to provide a protective sheath and to automatically neutralize the entrapped atmosphere. The lightweight Sen/Pak container heats more rapidly than the work piece. As a result, the undesirable elements in the entrapped atmosphere react with the Sen/Pak container long before the work piece is hot enough to be damaged by them. In addition, the Sen/Pak container acts as a protective barrier throughout the hardening and quenching operation.

After double tempering the rods will have a 315,000 psi tensile strength & a 210,000 psi yield strength at 58 Rockwell C. They will also have a Charpy impact value of over 224 ft-lbs. These rods will have no bushing or roller assembly in their top ends. They will run with the connecting rod's material directly in contact with the hardened wrist pins used. The upper & lower holes of the connecting rod will be aligned ground to each other in both axes within .0002"/6.000" by using a special designed holding fixture.

Jim Allen
« Last Edit: June 29, 2015, 12:28:12 AM by strictlybusiness1 »

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #156 on: June 29, 2015, 07:29:04 PM »
Again thank you very much for your contribution to the collective knowledge.

It's amazing how much extra work is included in order to reach the last bit of performance combined with reliability. But seeing that you reach 480 HP/L and I just got to 240 HP/L on my 50cc motoX bike in my youth (12 HP and I started with 2.5 HP) makes me realize that I would have been in trouble if I had any competition that had much more power than me. I could probably had reached 14-15 HP before my crankshafts and conrods wouldn't survive the extra power and then I would not be sure I could trust the gearbox either ....

Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #157 on: July 02, 2015, 09:36:56 AM »
I'm still quietly following and learning  :headscratch: Thank you again for keeping posting  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #158 on: July 02, 2015, 02:55:18 PM »
Thanks much Guys.

Admiral_dk, considering that Denmark is connected to Sweden by a bridge-tunnel, do you by any chance know Swedish tether car racers Nils Bjork, Jan-Erik Falk, Rune Granberg, or Mats Bohlin. Sweden They visited my machine shop in 2005 while competing at the US Tether Car Nationals held on Long Island. Information about the visit, with photos,  was posted on the Swedish Internet, September 7, 2005. These very advanced tether car modelers, some who held world records at that time & some who still hold world records, understand the value of  metallurgy, design mechanical engineering & in depth testing. Another person in the United States, who has done the same type of in depth tether car model engine development, as well as mechanical development of the car itself, would be John Ellis of New Jersey.

I presently work at Aero Precision Machine Inc located in Liberty, North Carolina, USA. The owner, Mike Langlois & I, build at this site, the world famous Nelson Q-40 pylon racing engines sold world wide. The engine's parts are manufactured on the best CNC lathes & mills available, to very tight tolerances (typically .00005"). All assembly & repair of these engines is done on site by myself. We intend to build now & in the future, the finest engine of this type any where in the world. The quality of every aspect of these engines, including Swedish custom bearings made by WIB, crankshafts, crankcases, cylinder machining, cylinder chroming & honing as well as hand fitting is done on site, under very tight controls.

There are no short cuts to be taken when attempting to build very high performance two cycle racing engines!!

Jim Allen



« Last Edit: July 02, 2015, 03:06:36 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #159 on: July 02, 2015, 08:58:19 PM »
Sen/Pak heat treating bags are shown in the two photos. Oil hardening steels that are sealed in these stainless steel bags will not be decarburized or have their surfaces dulled during heat treatment. It should be noted that oil hardened tool steels will not be hardened properly without the pieces coming in direct contact with the hardening oil. Therefore, holes will be punched in the bags after they are immersed completely in the hardening oil! The hardening oil is also heated 90* F to prevent thermal shock. A minimum of 5 gallons of standard hardening oil will be needed for connecting rods, crankshafts, front ends & induction valves.

Jim Allen
« Last Edit: July 02, 2015, 09:44:14 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #160 on: July 09, 2015, 11:02:49 PM »
The two connecting rods on the left have been heat treated & double tempered. Notice they have no scale from decarburization, but they do have a darkened color from being double tempered. The bottoms of the hardened & tempered rods were lapped on their outer surfaces to ensure a flat surface for the Rockwell test that was preformed. At the very bottom of each piece you can see the indentation mark from the diamond penetrater used in the hardness test. The rods are 56+ Rc hardness. The next step is to align grind, in two axes, the two holes to each other & have both holes to their finish dimensions.

Jim Allen

Online petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #161 on: July 11, 2015, 05:52:17 AM »
Sen/Pak heat treating bags are shown in the two photos.....Therefore, holes will be punched in the bags after they are immersed completely in the hardening oil!. Jim Allen

Very interesting, Jim
- are the foil bags themselves filled with an inert gas or something consumable to mitigate oxygen inside while being sealed up?
- is the general idea of punching the bag while submerged that oil floods in & contacts the steel (ie not atmosphere/oxygen)
- what does double tempering accomplish & what's the methodology? (ie a repeat of temper #1 or different temp/time recipe?)
- maybe I missed, but interested to know what heat treating oven you use

thx/Peter

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #162 on: July 11, 2015, 04:29:24 PM »
Sen/Pak heat treating bags are shown in the two photos.....Therefore, holes will be punched in the bags after they are immersed completely in the hardening oil!. Jim Allen

Very interesting, Jim
- are the foil bags themselves filled with an inert gas or something consumable to mitigate oxygen inside while being sealed up?
- is the general idea of punching the bag while submerged that oil floods in & contacts the steel (ie not atmosphere/oxygen)
- what does double tempering accomplish & what's the methodology? (ie a repeat of temper #1 or different temp/time recipe?)
- maybe I missed, but interested to know what heat treating oven you use

thx/Peter

A lot of intelligent questions asked here Peter, which I will try to answer.

There is no inert gas of any kind used inside the sealed, high chromium stainless steel, bags. "The lightweight Sen/Pak container heats more rapidly than the work piece. As a result, the undesirable elements in the entrapped atmosphere react with the Sen/Pak container long before the work piece is hot enough to be damaged by them. In addition, the Sen/Pak container acts as a protective barrier throughout the hardening & quenching operation." A preheating soak of the piece in it's bag at 1350*F to 1375*F is done first. Then the piece is raised to the  hardening austenitizing temperature of 1770*F to 1780*F & allowed to soak again. The entire bag is submerged in heated (90*F) standard hardening oil & holes are immediately punched in, which prevents the heated piece from ever being exposed to the atmosphere. After the piece has cooled to approximately  150*F, I use a double tempering operation at 400*F to bring the piece to it's final temper. At this point the piece is not clamped between the heavy steel pieces. The double tempering operation is only necessary for sections greater than 1.000" thickness. However, I have always, after cooling the piece to room temperature, tempered a second time at the 400*F temperature.

I use a Lucifer heat treating oven, with a digital temperature control, capable of holding the temperature at + or - 5 *F up to 2300*F. I use a Paragon High Fire Kiln with a Staco Energy Variable Auto-Transformer & an Omega HH-99A-K thermo-couple digital thermometer for tempering operations. I can hold  the tempering temper at + or - 2* F with the variable transformer controlling the voltage to the ovens heating elements.

Jim Allen
« Last Edit: July 15, 2015, 03:07:13 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #163 on: July 31, 2015, 02:38:41 PM »
The photos show some of the processes involved in making a fixture capable of grinding both the upper end & bottom end connecting rod holes parallel to each other in two axes at the same time. During the align grinding process the holes are also made to the correct size within + or - .0001". The connecting rods are through hardened & double tempered to give an ultimate tensile strength of 315,000 psi at 58 Rockwell C. With the custom double roller machined retainers shown they will be tested at 23,000 RPM.

In the upper part of the last photo can be seen the latest machined retainers & rollers to be used with stock Bi-Zeta connecting rods. They have 14 rollers, of the same size, compared to the stock retainer with 9 rollers. They are being tested at RPM's beyond 23,000 on my test stand. The small toe clamps at the bottom of this photo will hold the connecting rods in place after to locating pins are removed to allow through hole grinding.  Notice the use of two clamping screws, a jack screw in the middle & the slotted end of the fixture. After the hardened & ground .750" X .625" locating pin is zeroed (big pin at the bottom of the last photo), it remains in place while only the fixture is moved to automatically locate either hole for grinding. Since all holes are bored without moving the fixture, all holes in the clamped connecting rods ground with the fixture must be square & parallel in two axes at the same time. After final grinding they are square to each other within .0002" over 3.000".

Jim Allen
« Last Edit: July 31, 2015, 03:05:44 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #164 on: August 11, 2015, 01:41:49 AM »
I have now completed the holding fixture; it's locating pins for the upper & lower holes; the clamps for the upper & lower connecting rod ends; the hardened & ground mounting arbor, which when zeroed, will accurately  locate the fixture in the same location each time. This means each connecting rod will have the exact same center distance. In addition, each connecting rod ground on the fixture, will have both holes square & parallel to each other in two axes at the same time. I will set up the Themac tool post grinder & use gauge pins to grind the holes to the correct size.

The connecting rod is first located on the, clamped into position, locating pins. Then the rod itself is clamped to the top of the fixture with 4, 6-32 SHCS using the machined circular clamps. Unscrewing the top 10-32 SHCS's at both ends of the fixture & applying a slight amount of pressure with the two 10-32 jack screws in the middle at both ends, releases the locating pins, which now can pass out through the bottom of the fixture. Now the through hole grinding of the connecting rod's holes can be done & the mounting arbor, coming from the bottom of the fixture, can be securely clamped into position with the bottom two 10-32 SHCS's at both ends.

Jim Allen
« Last Edit: August 11, 2015, 02:12:47 AM by strictlybusiness1 »

 

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