Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 85658 times)

Offline Ramon

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #15 on: July 18, 2014, 10:11:31 PM »
Awesome - simply awesome - that truly is some extremely impressive work there Jim  :praise2: - not only in those superb parts and the finished engines but in the fixturing too - beautiful workmanship from an enviable knowledge base indeed.

I'm quite (but only just a little you understand ;)) envious of your heat treatment and cylindrical grinding facilities too - oh I wish ::)

Hoping to hear more about these fabulous creations

Regards - Ramon




"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #16 on: July 18, 2014, 11:37:39 PM »
Wow Jim that is a serious set of engines, I have a hydro that I run once and a while, nothing serious but by far the most fun to run out of all my r/c vehicles. May I ask where you are from?

Lexington. North Carolina

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #17 on: July 19, 2014, 12:13:57 AM »
Your research and development work is extremely impressive! I'm definitely looking forward to seeing everything that you share with us!

Your engine test stand looks like a useful fixture. Do you use it to run engines in or to get power measurements? Is propeller speed your primary method of determining an engine's performance or do you have a different method?

The engine test stand in my avatar is a custom made hydraulic dynamometer. It has an infinitely variable load capability, an electric tachometer that reads 0 to 50,000 RPM (every rotation) & a calibrated load cell with a digital readout to read the torque. I built this dyno in 1978 & rebuilt it in 2000. I use this to determine the brake HP of my engines. I also built two other HP measuring devices, one that would be described as a torque cradle which uses Dynamax fans as the load & another that uses various carbon fiber airplane propellers as the load.

The building of any engine would be very difficult, maybe impossible, without these instruments.  The photos show some of the key parts of the hydraulic dynamometer. It can absorb a maximum of 8 HP at RPM's exceeding 32,000. 1 HP is approximately 740 watts of heat. At 7 HP the rotor in the dynamometer housing absorbs 5200 watts of heat. The cold water comming in is heated instantly to 200 * F before it comes out. Dynamometer pulls usually last for 4 minutes at WOT.

Th hydraulic dynamometer shown has every piece doweled pinned in place. It can be disassembled & reassembled precisely without any type of alignment fixtures or jigs.

Jim Allen
« Last Edit: August 22, 2014, 01:17:19 AM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #18 on: July 19, 2014, 12:16:59 AM »
The first three photos are of the hydraulic dynamometer rotor housing. The piece is precisely machined & does not require any type of sealing. The adjustable valve at the bottom changes the amount of load.The remaining photos are of the torque craddle. It's RPM limit is 30,000 because of the Dynamax fan units used as a loading device. Different size rings mounted to the front of the 3/8 thick  protection shroud vary the load.

Jim Allen
« Last Edit: July 19, 2014, 12:35:34 AM by strictlybusiness1 »

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #19 on: July 19, 2014, 02:30:09 AM »
1 HP is approximately 4700 watts of heat.

1HP is 746W. Still, 7HP (5.2kW) is roughly 20% more heat than a typical gas stove top burner on max heat. Have you run any of the Nelson engines on the dyno?

Jim, great stuff as usual. I've been reading about your work since 2008 or before.

Greg

Offline Niels Abildgaard

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #20 on: July 19, 2014, 05:30:18 AM »
Please let us see a picture of crankshaft ,bearing and Coupling.What is mass of piston plus pin?.
The reason that You do not need needles in the upper conrod eye is that at 30000plus rpm piston is lifting against combustion pressure so that oil can come under pin.
For normal speed two stroke this is not the case .

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #21 on: July 19, 2014, 08:43:21 AM »
1 HP is approximately 4700 watts of heat.

1HP is 746W. Still, 7HP (5.2kW) is roughly 20% more heat than a typical gas stove top burner on max heat. Have you run any of the Nelson engines on the dyno?

Jim, great stuff as usual. I've been reading about your work since 2008 or before.

Greg

Thanks for correcting the misprint Greg. 740 watts is plenty & 4700 would not be possible.

JA

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #22 on: July 19, 2014, 10:23:02 AM »
Please let us see a picture of crankshaft ,bearing and Coupling.What is mass of piston plus pin?.
The reason that You do not need needles in the upper conrod eye is that at 30000plus rpm piston is lifting against combustion pressure so that oil can come under pin.
For normal speed two stroke this is not the case .

I had to search through my notes to find the mass numbers for entire rod assembly;
two rollers/ window retainer- .8 gms
16/ 0.627" OD rollers- 1.4 gms
steel "I" beam connecting rod- 12.5 gms
wrist pin (solid in the middle) .250" OD- 5 gms
piston- 15.6 gms

I believe that totals 35.3 gms & I use 33% of that total for the crankshaft counterbalance. The crankshaft weigh 132.4 gms.

I do not know if your thoughts about why no needles, rollers or bushing are not required on the top end is correct. The upper end assembly has .0001" total radial clearance & the bottom end has .0002" total radial clearance. The engine runs with .001" deck clearance without the piston hitting & the upper end of the rod is slotted for lubrication. I believe the metallurgy used prevents any galling or wear of the upper end parts. Notice that the upper end of the connecting rod is guided between the piston bosses without the use of any type of hardened thrust washers. The total axial clearance is .005". As to possibility of this working in a 125 or 250 cc two stroke racing engine, that question is unanswered.

I use the same type of connecting rod setup in my 22,000+ RPM, 26 cc gas engines. There have been no problems thus far. I believe that the squareness & rigidity of the engine's crankcase plays a major role in what is happening after the engine comes to temperature.

The next to last photo shows the entire roller assembly in place as it is used. Look carefully & the two rollers in each window of the retainer can be seen. The partial print shows the numbers involved with the bottom end roller assembly used in the 26 cc gas engines. The machining of the retainer proved to be essential in the building a very high RPM roller assembly. Since the rollers are guided along their center lines, from end to end, there is no skewing possible. The friction & heat that some thought would develop from two rollers touching dose not occur. The retainers are always guided in ID of whatever bore is used, with .001" total radial clearance. Notice that the retainers width at the center line of the rollers is .025" wide. The very low mass of the retainer & the tight radial clearance helps to decrease roller skidding to a minimum.

The second photo from the top shows how the crankshaft is mechanically fastened to the inner races of both front bearings by placing a hardened steel sleeve over the crankshaft between the two inner races. Since all the parts are made of steel, including the full hard AISI O-1, ground ID & OD front end, the axial play can be set when the engine is cold. It remains the same amount when the engine comes to temperature. The third photo shows the steel shim washers used with the hardened steel sleeve to set the crankshafts axial play at .004".

Jim Allen
« Last Edit: July 19, 2014, 11:05:54 AM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #23 on: July 19, 2014, 10:48:39 AM »
1 HP is approximately 4700 watts of heat.

1HP is 746W. Still, 7HP (5.2kW) is roughly 20% more heat than a typical gas stove top burner on max heat. Have you run any of the Nelson engines on the dyno?

Jim, great stuff as usual. I've been reading about your work since 2008 or before.

Greg

We have run many of the Q-40 & FAi engines with our standard test props. Dyno tests show that the FAI engine can produce approximately 4.5+ HP at 30,000 RPM on 15% fuel. We have used a data logger to determine the RPM's of the Q-40 engine in the air on a three pylon course. The engine reaches approximately 29,000 on the straights & loses approximately 500 RPM when turned. Speeds on the straight measured with a Stalker gun are approximately 200+ MPH. We have been able to raise the quality & consistency from engine to engine with our very detailed engine building program. At Aero Precision Machine, high precision machines such as Makino, Mori Seki & Bridgeport are available to produce very high precision parts. Each & every engine is assembled by the numbers, by me.

Jim Allen

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #24 on: July 19, 2014, 12:56:50 PM »
Whoa - you are working with stuff I used to dream of as a kid and young man and I'm impressed with the numbers too. They stopped racing 125 cc road racing motorcycles a few years back and they had reached some 430 HP/litre and you where at 482 HP/litre years ago  :NotWorthy:

I got plenty of questions, but right now I just want to ask three :

Your engines are the first where I can see very little clearance between the inside of the piston and the top end of the rod - why - is it to avoid problems at the bottom end of the rod ?

How do you ensure that you only plate the inside of the cylinder when all of it is in the electrolyte or have I misunderstood your pictures ?

I'm really interested in the plating process - it can be used on many other cylinders than those intended for the power part of a two stroke - is this a "standard chroming process" or is it hard chrome and what is the difference - electrolyte etc. in case it's not (the short version) ?

Thank you very much for sharing  :praise2:  :pinkelephant:  :praise2:

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #25 on: July 19, 2014, 03:28:11 PM »
"Your engines are the first where I can see very little clearance between the inside of the piston and the top end of the rod - why - is it to avoid problems at the bottom end of the rod ?"

Yes. Notice that the upper end of my connecting rod is wider than the bottom end. In fact it is .375" wide in the top compared to .3125" wide in the bottom. Guiding the connecting rod in the bottom end can lead to frictional heat problems because the rotational speed in the bottom is high. Upper end guidance allows the bottom end to have a liberal amount of axial clearance (in my engines .015") , but keeps the connecting rod centered. There is no tilting of the cylinders axis to keep the connecting rod from moving off the cantilevered crankshaft when it is bending under load. Also the crankshaft of my engine has a  large diameter for an engine this size, .5906"  (15 mm). This helps to reduce the bending. Consider the crankshaft size used in all manufactured 23 to 30 cc engine is .4724" (12 mm). Even though these crankshafts are the three piece split type, with bearings on both side,  the bending still takes place. This would be true even in engines with four bearings, two on each side.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #26 on: July 19, 2014, 03:42:22 PM »
"How do you ensure that you only plate the inside of the cylinder when all of it is in the electrolyte or have I misunderstood your pictures ?"

More photos should answer this question. The cylinder sits inside a brass sleeve which sits inside a PVC fixture. The PVC fixture enables the cathode connection to the cylinder & locates accurately the lead antimony anode in the center. The sleeve the cylinder sits in has purposely been made longer at the top & bottom of the sleeve to prevent a buildup of chrome at the top & bottom edge of the cylinder.

Jim Allen

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #27 on: July 19, 2014, 03:52:18 PM »
Thanks for that. I was curious how much power Q40 engines were making. I saw mention of 4+HP and didn't realize they were making that much these days.

Greg

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #28 on: July 19, 2014, 04:07:00 PM »
"I'm really interested in the plating process - it can be used on many other cylinders than those intended for the power part of a two stroke - is this a "standard chroming process" or is it hard chrome and what is the difference - electrolyte etc. in case it's not (the short version) ?"

There are two basic types of chrome platting, decorative chrome plating (shiny stuff) & hard industrial chrome (not shinny). I use the standard Chromic Acid/Sulfate Bath mixed at a ratio of 100 to I. For example 33.3 ozs of CrO3 & 0.33 ozs of H2SO4 are mixed  in 1 gal of distilled H2O.  The bath is run at a current density of 3 amps/ sq in, including the brass fixture,  at 125* F. For a .90 size cylinder & fixture it takes 21 amps at 4.6 volts to plate .001" of chrome/ hour on the cylinder's ID. The bath's temperature & the current density will determine how hard the chrome plating will be. If done correctly the hard industrial chrome plating applied will exceed 1100 vickers. Carbide tools will have not effect on scratching this.

I also chrome plate 4032 aluminum cylinders, but the cleaning & etching process is much more involved. The cleaning of brass pieces is done with a strong alkaline solution. Steel pieces are reversed etched before the chroming process is started.

Jim allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #29 on: July 19, 2014, 04:18:36 PM »
Thanks for that. I was curious how much power Q40 engines were making. I saw mention of 4+HP and didn't realize they were making that much these days.

Greg

We began to do some testing with the torque craddle at RPM's beyond 32,000. In fact the loading device we attempted to use was made of aluminum & was designed to withstand 40,000+ RPM. However, the device's mass prevented it from working at the higher RPM's. Sometimes careful calculations & design do not work out when cut & try time comes. The loading device certainly looked good on paper.

Jim Allen