Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129718 times)

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #75 on: August 30, 2014, 03:32:11 PM »
I see the air bleed needle under the barrel.  I have your detailed pictures and sketches, but I bet others would like more information on exactly how this all fits together and works. 

Lohring Miller

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #76 on: August 30, 2014, 04:58:49 PM »
I'll try to take more photos of the air bleed track itself. It is a separate part that attaches to the carburetor body with 4 of  the existing 8,  2-56 screws. The part's outlet opens into the 1/8" diameter hole in the carburetor's body. The position & size of the air bleed hole was found through trial & error. For this engine, with this pipe & this .625" bore carburetor, the air bleed begins to open just past 1/2 throttle closing. 7 degrees beyond this point the air bleed hole is 1/2 open.  The amount of air being admitted is very sensitive in controlling the engine at lower throttle settings. If there is to much additional air being admitted, then engine will begin to rev up as the carburetor barrel is closed below 1/2 throttle. If there is not enough air, then the engine will load up & stop running.

I am guilty of not making detailed prints because they are not needed when machining most parts. I make partial sketches with important numbers & usually begin cutting using thoughts in my mind. The posted photo shows the exact position & size (.1250") of the air bleed hole on the carburetor presently being used. In the first photo, if you look carefully, the black dot at the bottom of the carburetor's bore adjacent to the rotating barrels edge, is the air bleed hole. Its size & position are very similar to a .725" bore carburetor being tested which uses the same type of air bleed system. Many people say the air bleed system can not work over a wide range. In my opinion, from many hours of in depth testing, they are completely misinformed.

Jim Allen 
« Last Edit: August 30, 2014, 05:24:27 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #77 on: September 07, 2014, 06:45:05 PM »
The engine's power is absorbed & converted into heat by the water vortices created between the rotor & the housing holes. The resulting drag applies a resistance to rotation & with an equal effort turns the dynamometer housing mounted in the trunnion bearings. The distance from the center of the dynamometer housing to the center of the load cell is exactly 6.000". Since the torque arm's movement is only .005", there is no tangent error to consider when reading torque amounts. Notice the lightening slots machined in the torque arm. This small amount of out of balance causes the dynamometer housing to rotate in the very low stick slip, Rulon bearings, which were aligned bored after the cradle was assembled. The calibrated Omega model LCF load cell with a + or - 5 lbs. range & a safe overload of 150% is not fastened to the torque arm. The special designed ball adaptor sits on the load cell's stud to prevent errors which could be caused by any misalignment. The ball adaptor also has a screw thread on its top end, which allows weights to be attached for accuracy checks, after zero setting the load cell at the digital meter. Notice the very rigid mounting of the load cell's solid one piece machined base which ensures rigidity & squareness to the dynamometer housing. The load cell base can be adjusted up & down to allow the torque arm to be adjusted perpendicular to the load cell axis. The cost of the calibrated load cell was approximately $550.00 dollars. The digital panel connected to the load cell reads the applied force in lbs. to two decimal points & it is shock mounted. Its cost was approximately $650.00 dollars.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #78 on: September 14, 2014, 11:04:48 PM »
One of the most important mechanical parts of any engine test stand is the type of universal used to transmit the engine's HP. Constant velocity, mechanically reliable universals will become necessary because it will be impossible to perfectly align the various rotating parts. I machine the precision ball & pin type universals seen in the photos. All the male ball ends & the slotted female ends are machined from heat treated AISI 0-1 tool steel. The drive pins are made of hardened M-2 steel reamer blanks.

A detailed explanation of  how to make these pieces will follow. They have been tested on various engine test stands as well as on actual models at speeds above 32,000+ RPM & 7.5+ HP.

Jim Allen
« Last Edit: September 28, 2014, 03:18:14 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #79 on: September 28, 2014, 03:09:33 PM »
I have received several e-mails with questions about how to hard chrome plate engine cylinders for use in high performance two stroke engines. There are two basic material types presently being used, aluminum & brass.  Both can be efficiently & easily plated with properly designed fixtures in the basic chromic acid/sulfate bath. Finishing of chrome plated cylinder bores needs to be done by honing or grinding. Precise measuring of the bore's taper & the bore's roundness is also necessary. Honing & measuring can be done with standard types of Sunnen equipment.

Jim Allen

Offline WingRacer

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #80 on: September 28, 2014, 03:20:32 PM »
Thx you Jim for your post!

Roy

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #81 on: September 28, 2014, 04:17:42 PM »
One important part of the chroming tank is the lead antimony anode. It needs to be placed in the center of the cylinder's bore to ensure that an equal amount of chrome is plated on the cylinder's ID. Chrome tanks have very poor throwing ability which means a very high current density & closeness of the anode to the part being plated are necessary. The photos show the casting mold & the finished machined lead antimony anode positioned on center by the PVC fixture. At a current density of 3 amps/ sq in (total of 24 amps), the tank will give .0012" of chrome/ side/ hour in 2 hours. Also, the bath must be maintained at 125* to 135* F.

Jim Allen
« Last Edit: September 28, 2014, 06:55:10 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #82 on: September 28, 2014, 06:51:56 PM »
The outside brass sleeve, which the cylinder sits in, makes positive contact between the two stripped cathode wires & the cylinder. The large clamping nut & the top brass ring clamp all the pieces together securely. The outside brass sleeve is also relieved in it's ID in the areas where the cylinder's windows are. This is necessary because there will be a small build up of chrome in these areas making removal of the cylinder impossible. All pieces are machined as a slip fit.

Another reason that the outside brass sleeve & the top ring are necessary is that they prevent the chrome from building up at the top & bottom edges of the cylinder's bore. Any chrome plated on the bottom & ID of the outside brass sleeve as well as the ID of the top ring can be removed with a 50% solution of hydrochloric acid.


Jim Allen

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #83 on: September 28, 2014, 07:07:23 PM »
Even though you showed (most of) these pictures before, I would like to thank you for sharing your knowledge with the rest of the world (or at least those of us following this thread  :praise2:

Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #84 on: September 28, 2014, 07:18:17 PM »
I think that there are a lot of people following this thread, but in my case it is so far advanced I struggle with some of it  ::) There is still at lot to learn though  :) Please keep posting  :cheers:
Best regards

Roger

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #85 on: September 28, 2014, 11:18:39 PM »
If anyone is interested, the hard industrial chroming of aluminum cylinders will be explained in detail. This is presently being done on the 4032 aluminum sleeves used in all the Nelson Q-40 pylon racing engines. The process involves several different chemicals with the same type brass fixture, PVC holding fixture & CrO3, H2SO4 bath. The chrome plated on aluminum is as hard ( approximately 1100 Vickers) as any plated on a steel or a brass piece. The only real difference is in the cleaning & etching processes involved.  Many engine manufacturers have given up on chroming aluminum cylinders because of this.

Jim Allen

« Last Edit: September 30, 2014, 09:16:19 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 #86 on: September 29, 2014, 07:56:05 PM »
Oh yes please !!!!

Will it make any difference with different aluminium types / any to be avoided ?

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #87 on: September 30, 2014, 02:47:19 AM »
I have not chromed different aluminum types, but I think there will not be any problem if the procedure is done properly. This is also true for different types of brass or bronze alloys. I will "CAREFULLY" write up the procedure & post it sometime this weekend. There are several chemical solutions that must be used with specific time amounts for each solution before placing the cylinder in the chroming fixture. Washing is done with Dawn dish washing detergent & hot water.  If done properly the chroming can be done without any blistering or pitting. Aluminum sleeves that are not chromed properly can only be saved by grinding all the chrome off.

Jim Allen
« Last Edit: September 30, 2014, 02:51:43 AM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #88 on: October 17, 2014, 04:48:22 PM »
I have successfully hard chrome plated 4032 aluminum cylinders, 360 free machining brass, 544 phosphorous bronze & steel parts in the standard, basic 100 to 1 chromic acid/sulfate bath. The following chemicals & procedures have been used for more than 25 years to hard chrome plate 4032 aluminum cylinders. Chemicals & solutions for chroming aluminum must be stored in polypropylene jars with polypropylene covers. A well ventilated room, a removable filter type oxygen mask & rubber gloves should also be used when chroming. The chrome tank itself, which will contain heaters, a liquid measuring thermometer & a exit hole for the cathode wires will be sealed during the chroming process.

The mixing of all chemicals should be done with a protective rubber apron, rubber gloves & a face splash shield. All chemicals are mixed by volumes in their particular ratios.

1. Mix hydrofluoric acid & nitric acid in a 1 to 3 ratio by volume.
2. Mix nitric acid & water in a 1 to 1 ratio by volume
3. Mix zincate & water in a 2 to 1 ratio by volume.

The procedures are as follows;

1.With rubber gloves on, clean the cylinder's ID twice with Dawn dish washing soap & hot water. Use a round nylon brush to scrub the cylinder's ID. While holding the cylinder, only on its "OUTSIDE", with a formed aluminum wire, place the cylinder & aluminum wire holder in the hydrofluoric & nitric acid solution for 30 seconds. Agitate the piece & solution together. Remove & rinse in hot water.
2. Place the cylinder with formed wire in the zincate & water solution for 60 seconds. Agitate the piece & solution together. Remove & rinse in hot water.
3. Place the cylinder with formed wire in the nitric acid & water solution for 5 seconds. Remove & rinse in hot water.
4. Place the cylinder with formed wire in the zincate & water solution for 90 seconds. Agitate the piece & the solution together. Remove & rinse in hot water.
5. Place the cylinder, with it's brass holding fixture, in the preheated chrome tank after attaching the anode (positive) & the cathode (negative) contacts. All connections "MUST" be positive, solid connections. With the power turned on, place the entire fixture in the chrome tank. The current should immediately begin to read!! Use the half current amount for approximately 8 to 10 minutes & then the full current amount for 90 minutes. The full current amount is calculated from the total area of the cylinder & it's brass holding fixture, divided by the current to give 3 amps/ sq in.

With a lead antimony anode of 1/4" diameter, the tank should be able to put on .001" to .0015" of chrome/ side. Improper cleaning, etching or bad contacts will result in blistering, pitting or poor deposit thickness. If done properly, with a bath temperature of 125* to 130* F, a current density of 3 amps/ sq in, the plating should be approximately 950 to 1,025 Vickers. This means the plating can not be cut with any type of carbide tooling!

More detailed pictures to follow & possible a video, if time allows this.

Jim Allen



Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #89 on: October 18, 2014, 08:23:07 PM »
That's some serious effort  :praise2: Still following and learning  :ThumbsUp:
Best regards

Roger

 

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