Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 98689 times)

Offline Old School

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #270 on: February 20, 2018, 09:30:35 AM »
I am interested in your work on tuned pipes, I don't know much about the boats you run. Will the boat accelerate and come onto the pipe without any any outside assistance?

I run tethered cars but we have a guy in the centre who will horse them up to a speed were the pipe will start to work and the car then accelerate away that speed is around 100mph.

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #271 on: February 20, 2018, 11:22:10 AM »
I thought that the trend with tethered cars now was to use variable exhaust ports as in the full sized engines - so you start with a low port and opens the port as speed increases  :noidea:

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #272 on: February 21, 2018, 09:55:43 AM »
I am interested in your work on tuned pipes, I don't know much about the boats you run. Will the boat accelerate and come onto the pipe without any any outside assistance?

I run tethered cars but we have a guy in the centre who will horse them up to a speed were the pipe will start to work and the car then accelerate away that speed is around 100mph.

I am familiar with tether car type tuned pipes. They are usually made of steel or titanium, never aluminum, because of the high "G" forces (10 to 12 times the cars weight) that the car will be subjected to when running at its maximum speed. I visited the track located on Long Island many times when I lived in Huntington, L.I., N.Y. I have witnessed speeds over 200 MPH by racers such as Guitterio Picco & Mats Bohlin in the .60 cu in class. Other well known racers such as Jan-Erik Falk, Nils Bjork, Rune Granberg, John Ellis, Jack O'Donnell, Erik Strobel & others from around the world competed in the world class events held there. This track was developed & sponsored by Dr. Anthony Tucci. It is one of the best tracks in the world! Many of these racers visited my machine shop located in Huntington.

All tuned pipes are similar & they work on the same principles. With that said, be aware of the infinite diffuser angles & lengths, baffle angles & lengths, major diameters & lengths, stinger ID's & lengths that could be used in making a tuned pipe.

Jim Allen
« Last Edit: February 21, 2018, 04:38:04 PM by strictlybusiness1 »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #273 on: February 21, 2018, 08:46:38 PM »
James,
 I'd like to switch gears for a minute and ask about the billet block construction of these engines. Did you possibly use a broach to cut the crankcase transfers in these?  Are you willing to share photos of the transfers and or the process to cut them? Beautiful work BTW.

 

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #274 on: February 23, 2018, 12:01:47 AM »
Okay.

I have to get the necessary drawings & photos together in order to give an understandable explanation.

Please be patient?

JA

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #275 on: February 23, 2018, 02:58:20 PM »
You can find a lot of Jim's work pictured in the International Waters gallery (sign in required).  He has great explanations under the pictures as well.

See http://gallery.intlwaters.com/index.php?cat=10141

Lohring Miller

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #276 on: February 24, 2018, 12:00:39 AM »
The cutting of the transfers was never explained fully because this was a proprietary process at that time. No other bar stock, one piece, engine crankcase  at this time could be made with the entire transfer profile being cut from the inside. The final size, depth & shape of the transfers was developed with the cut & try method.

We learned that the thickness of the cylinders wall not only has a greater influence, but is the determining factor, on what direction the incoming & exiting gas must travel. The photo shows what can happen if the radial or axial angles of the transfers are cut incorrectly in a liner which has the proper thickness!! The red lines are the radial angles cut on the main transfers closest to the exhaust window. Re-cutting the angle on the main transfer windows closest to the exhaust window from 33 deg 30 min to 43 deg 30 min eliminated this problem. Final dyno test of this .80 cu in engine showed 6.2 to 6.8 HP at 24,000 to 26,000 rpm on 65% nitro fuel. I used this engine, with the re-cut liner and new piston, to set my first NAMBA straight away record at the NAMBA Nationals in Washington, DC in 1990.

JA
« Last Edit: February 24, 2018, 01:28:00 AM by strictlybusiness1 »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #277 on: February 24, 2018, 03:21:33 AM »
Lohring,
You don't have to be signed into intlwaters to see Jim's gallery or explanations. Thank goodness..... His IW gallery has had its own google link for years now.  Just type in Google's search bar Jim Allens .90 engine


Yes James,
 I knew it was proprietary and not included there. We talked about it years ago... I have all the patience in the world. Thanks in advance....

« Last Edit: February 24, 2018, 03:30:55 AM by DRT »

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #278 on: February 24, 2018, 03:37:03 PM »
That's good news.  I'm signed into International Waters so I automatically assumed that it was required.  More people need to see how to build high performance engines.  The art is being lost.

Lohring Miller

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #279 on: February 25, 2018, 04:30:55 PM »
I forgot to mention that while the engine was running at WOT, the center post of the glow plug began to glow red. It was Bill Wisniewski's suggestion to recut those main transfer angles to eliminate this problem. In fact, with the angles re-cut at 43 deg 30 min,  the engine could be over leaned at WOT without burning the plug out. This also taught us that the directions of the incoming charge will have a great effect of how much compression the engine can stand before detonation sets in. The better control of where the incoming charges were being directed was a direct result of changing the wall thickness of the cylinder from .060" to .125". Everything else in the engine was the same!!

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #280 on: March 17, 2018, 08:18:44 PM »
Sometimes it becomes necessary to repair & modify a favorite tool. The Fowler ULTRA-CAL II electronic caliper was disassembled & has the 5 original permanent rivets replaced with 5 precision machined removable rivets. This allows the entire unit, including the P/C board, LCD & wipers mounted in the calipers cover to be easily removed for deep cleaning. The caliper works as well as it did when purchased 25 years ago. Its calibration has been checked.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #281 on: May 27, 2018, 04:25:07 AM »
James,
 I'd like to switch gears for a minute and ask about the billet block construction of these engines. Did you possibly use a broach to cut the crankcase transfers in these?  Are you willing to share photos of the transfers and or the process to cut them? Beautiful work BTW.

 

Here are some photos of the boost ports & main transfers. The tops of these ports were cut first & then the remaining material was broached with a special tool to be shown at a latter date. The darker colored crankcase, which was made of steel, used the same techniques to cut the transfers from the inside of the cylinder. Drawings of the shape broached into the cylinder walls will be shown at a latter date. The .200" thick lip used on the cylinder lowered the crankcase height by this amount which made cutting from the top possible. More details on this to follow.

Jim Allen
« Last Edit: May 27, 2018, 04:29:00 AM by strictlybusiness1 »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #282 on: May 30, 2018, 12:18:24 AM »
Thanks a lot for sharing this information. Nice work!  :happyreader:
« Last Edit: May 30, 2018, 05:20:49 AM by DRT »

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #283 on: May 30, 2018, 11:46:10 AM »
Thank you again Jim for sharing.

I have a few questions though. On bigger engines there's usually 4 main transfer ports and one or two boost ports, but you have three boost ports and only two main transfer ports ... why ?

One of the pictures show the main transfer port and the top looks to be turned a bit toward the exhaust - is that a slightly blurred picture, an optical illusion or perhaps the earlier mentioned adjustment of the main transfer port to avoid overheating the plug ?

Best wishes

Per

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #284 on: May 31, 2018, 10:37:47 PM »
The reason I used 3 boost ports & 2 main ports is because the design was copied from the the OPS engines I ran before building my own engines. I discovered later on that what was done as far as the radial & axial angles machined in the cylinder was much more important in controlling the directions of gas flow. I discovered this by accident when the typical cylinder wall thickness was changed from .060" to .100". None of the transfer valleys in the crankcase are turned in any radial direction as is shown by the posted prints & they are all the same depth. However, there are many different radial & axial angles cut in the .100" thick cylinder wall on the boost, main transfer & exhaust windows. Duplicate windows that match in the cylinder's wall must be siamese twins in the radial & axial directions.

Jim Allen
« Last Edit: June 01, 2018, 10:33:23 AM by strictlybusiness1 »