Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129714 times)

Offline 90LX_Notch

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #195 on: November 25, 2016, 10:12:49 PM »
Glad to see you back Jim and will be looking forward to more education from you  :praise2:

Best wishes

Per


X2, I really find this thread facinating.

-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 #196 on: December 01, 2016, 12:46:29 AM »
The first photo shows a complete chroming tank with heaters. The chrome tank is maintained at 130 deg. F & is run at a current density of 3 amps/sq. in. The total current required for the brass holding fixture & the liner is 24 amps. The brass holding fixture prevents the build up of chrome on the top & bottom of the liner. This build up takes place on the fixture & is removed afterwards with a warm 50% solution of HCL acid. At a current density of 3 amps/sq.in., .0012" of chrome/side/hr. will be deposited. In 2 to 2.5 hrs., a total of .0024"+ of chrome will be deposited on the liner's inner wall. If done properly, this simple bath will deposit smooth chrome with a hardness of 1,000 Vickers. Carbide tooling WILL NOT cut even 900 Vickers Chrome.

The second photo shows a Simpson DC amp meter & volt meter with hook up wires plus an on-off switch.

The third photo shows an Astec model LPS-252 switching power supply. The power supply has an output of 3 to 6 volts at 50 amps with +-2% regulation & a 50 mv ripple.

More explanations to follow.

JA

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #197 on: December 01, 2016, 12:53:37 AM »
Here are some photos of the inside of the fixtures used to chrome brass or aluminum cylinders. The last photo are samples of aluminum cylinders that I chromed today.

JA

Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #198 on: December 01, 2016, 09:25:43 AM »
Fascinating work  :ThumbsUp:  :ThumbsUp: I'm still learning  :headscratch:
Best regards

Roger

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #199 on: December 02, 2016, 03:18:08 AM »
These photos show the chroming tank in operation. The entire tank is placed inside a foam cooler which helps to stabilize the tank's internal temperature. The positive voltage is connected to the anode & the ground is connected to the cathode (liner inside wall) where the chrome is deposited. This particular cylinder is for a .45 cu in engine. It requires 11.5 to 12 amps at 3.8 to 4.2 volts for 80 minutes to give enough chrome build up for the final honing process.

JA

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #200 on: December 09, 2016, 10:28:59 PM »
This is how the fixture is supported in the chroming tank. Notice the two silicon coated wire leads (cathode) passing through the tanks cover that are connected to the cylinder sitting inside the brass holding fixture. Also notice the 1/4" lead antimony (anode) which supports the entire unit & is held in place with a split collar. Quality rubber gloves & a respirator type mask are used at all times when using the chrome tank. There will be some chrome that plates on the holding fixture's inside wall (through transfer & exhaust windows) & at the top & bottom of holding fixture. The build up at the top & bottom of the fixture prevents any unwanted buildup at the top or bottom of the cylinder. Any plating on brass pieces is removed by placing those pieces in a 50% solution of warm hydrochloric acid.

Next will come the necessary chemicals & the procedure needed for successful chrome plating of aluminum alloys. Most engine manufacturers prefer to chrome plate brass cylinders because the only required cleaning solution is an alkaline wash. THIS IS NOT THE CASE WITH ALUMINUM!

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #201 on: January 30, 2017, 07:17:05 PM »
The necessary chemical solutions needed for the successful chroming of aluminum alloys must be kept in polypropylene containers with polypropylene covers. Quality rubber gloves, a respirator type oxygen mask, rubber apron & face splash shield are also used at all times when handling these chemicals. All chemicals are mixed according to volume only. The special holder shown in the upper right hand corner of photo #1 allows the cylinder to be placed in the solutions & rinsed without any contact.

1. Mix 1 part Hydroflouric acid with 3 parts of  Nitric acid.
2. Mix 2 parts of Zincate with 1 part of distilled water
3. Mix 1 part Nitric Acid with 1 part of distilled water.

Since the cleaning, etching  procedure is time sensitive, a clock & the necessary time lengths are posted in clear view.

1. Place the cylinder in solution number 1 for 30 seconds. Remove & rinse in hot tap water.
2. Place the cylinder in solution number 2 for 40 seconds. Remove & rinse in hot tap water.
3. Place the cylinder in solution number 3 for 5 seconds. Remove & rinse in hot tap water.
4. Place the cylinder in solution number 2 for 120 seconds. Remove & rinse in hot tap water.

Place the cylinder mounted in the fixture in the heated chrome tank with the power turned on. The tanks temperature is maintained at 125* to 130* F. The starting current is 1/2 the amount needed to give a total of 3 amps/ sq in. For the area of theses cylinders 6.5 amps is used for 5 minutes & then the current is raised to 13 amps for 75 more minutes. The full current amount is calculated from the total area of the cylinder & its brass holding fixture divided by the current to give 3 amps/ sq in. The 75 minute plating time gives approximately .001" to .0015" of chrome/ side.

Jim Allen
« Last Edit: January 30, 2017, 07:21:45 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #202 on: April 24, 2017, 02:45:48 PM »
The hard chroming process is not complete without proper honing or grinding of the plated surface. At Aero Precision we use a Sunnen Honing machine & the simple holding fixture shown to quickly hone cylinders round within .00005" & also to the correct taper. Each cylinder is checked during the honing process with a Sunnen bore guage to tight tolerances.
 
Jim Allen

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #203 on: April 24, 2017, 09:48:02 PM »
Seeing all that it involves to fabricate one of these marvels makes one realize how fair the price actually is compared to the normal sport engine.

Again thank you for showing us  :NotWorthy:

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #204 on: April 24, 2017, 10:17:01 PM »
I'm also deeply involved with the development of tuned pipes for nitro and gas engines. Some of the chambers being tested are rolled & others are machined from thick walled tubing. This is another story to be told, maybe some day.

JA

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #205 on: April 25, 2017, 12:55:30 PM »
Expansion chambers for two-stroke engines are another very interesting subject for some of us here, so I got a question :

I have seen several software programs that can calculate two-stroke engines from 50cc and up, but never any for smaller engines - so do you calculate your own or is there a program I haven't seen ?

By the way - very nice looking system you are building in the pictures above.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #206 on: April 27, 2017, 08:17:28 PM »
I use 2 Stroke Wizzard 5 only as a reference, but always keeping in mind what has been learned from many hours of dynamometer testing. For example, a calculated chamber for a single cylinder 26 cc engine operating in the 19,000 to 22, 000 RPM range would have a major diameter of 2.455" & a baffle cone angle of 27*. Actually the best tuned pipe for my application would have a major diameter of 2.5" to 2.7" & a baffle cone angle of  22*. Another important consideration is the volume of the chamber in comparison to the displacement of the engine. No single program that I know of gives an absolute answer as to what would work best.

The photo shows the next section of the diffuser before it is parted off. A .010" deep X .050" long undercut will be machined before the piece is parted off. One more section after this & the chamber will be ready for silver soldering. Notice the heavy, water soaked  brown rapping paper inserted "tightly" inside when machining the OD. It changes the chatter frequency & allows the piece to be machined down to a .022" thick wall without any chatter.

Jim Allen

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #207 on: April 28, 2017, 11:37:12 AM »
Thank you very much Jim

I just ordered the software at $35 until May 1st. it's a no brainer for software that includes model engines - admittedly not diesels (CI) but I can live with that. I expect that some of the problems / differences you encounter has to do with the fact that you can't tell the program what exhaust temperature you have, but "only" chose fuel type - still for a program this cheap, no problem  :)

Thanks for the trick with the paper - nice to know  :ThumbsUp:

Best wishes

Per

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #208 on: April 28, 2017, 01:26:17 PM »
Sorry for getting off the main topic here. In order to make effective use of the necessary chemicals involved in hard chroming plating of aluminum alloys, the simple cylinder holding fixtures shown were made from 1/8" diameter soft aluminum rod. Only the cylinder & its holding fixture are inserted in the chemicals for the specified amount of time. The only other contact with the cylinder is when it is removed from this fixture before being placed in it's brass holding fixture. This is done with rubber gloves by touching only the cylinder's lip! This may sound complicated or difficult, but it is really very easy to do when the holding fixture is properly made. The holding fixture also makes it very easy to wash the cylinder & the 1/8" diameter holding fixture in hot tap water in between each insertion in the chemicals.
 
Jim Allen

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #209 on: April 28, 2017, 03:01:18 PM »
Expansion chambers for two-stroke engines are another very interesting subject for some of us here, so I got a question :

I have seen several software programs that can calculate two-stroke engines from 50cc and up, but never any for smaller engines - so do you calculate your own or is there a program I haven't seen ?

By the way - very nice looking system you are building in the pictures above.

All tuned pipe formulas are at least partially empirical.  Gordon Blair published a program years ago that most of the newer formulas copied.  My current favorite is from Frits Overmars based on the drawing below.  Be sure you have some idea of the average exhaust gas temperature in the pipe.  The only way to check a design without building it is an engine simulation program.  Even so I believe there's no substitute for dyno testing.

Lohring Miller

http://www.underdogsracing.com/fospipe/

 

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