Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129371 times)

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #120 on: December 29, 2014, 04:02:45 PM »
Jim

The interesting thing here is mass.The flywheel and crank can be half mass  of a single.Port areas are up,piston speed less for same rpm if geometry ,ie bore/stroke ratio is the same and the charge air pumping is done by two resonant exhausts instead of one.To See if this kind of reason is valid it could be fun to scheme one as competitor to the configuration You have now,being State of art I would say.
Have You ever considered releasing drawings to us two stroke lovers?
The real stumbling block is to make a non overhung crankshaft that stands rpm on the far side of 500 rpm and still allowing this enormous flow of air and fuel.I will try to reread the whole thread and see how much dimensions You have given already.
It has been a wonderfull mental journey until now.
A happy new Year to You and all Your admireres.

Thank you Niels, but you would be appalled at the quality of the prints, sketches or drawings used to make this stuff. I have always been able to machine parts with a visual idea, some key dimensions, & drawings made on .100" grid graph paper. Many times I draw things at a ratio of 1 to 20 & take measurements directly from from the drawing with a machinist scale. No Solid Works, Auto Cad or Pro-E used or CNC equipment ever used. Most of the tools & machines I use would not be familiar to present day machinist.

Jim Allen

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #121 on: December 29, 2014, 04:26:40 PM »
Here are more examples of "taper masters". The pieces at the bottom are used to cut taper amounts that vary by .001" over a distance of .100" on pistons. The piston's circumference at it's top is tapered for use in tapered cylinders. The pieces are machined 20X longer in length to make setting of the compound accurate. For a .001" taper per side, the diameter at both ends vary by .020" over a distance of 2.000". The top pieces in the photo are used to cut or grind tapers in cylinders. They are 2X the actual length of the 1.635" length needed. The diameters at both ends vary by .001" but over a distance of 3.270".

Jim Allen
« Last Edit: January 09, 2015, 11:32:34 AM by strictlybusiness1 »

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #122 on: December 29, 2014, 07:31:59 PM »
- A Themac tool post grinder, turning at 20,000 RPM, is mounted to the compound to grind the cylinder's ID taper.
- Since the ID of the collet is much smaller then the ID of the cylinder, the grinding stone's RPM is raised to 40,000. I prefer to use a Themac tool post grinder because it is the only tool post grinder that allows precise centering of the grinding stone's center, with its unique rotating mounting of the spindle.
Jim Allen

Fascinating. Thanks again. You just answered my next question about tool post grinder. I guess its safe to say a jerry rigged die grinder would have insufficient accuracy, bearing/runout etc. attempting this level work? Would you mind telling me your model number or recommendation for ~14" swing lathe. I'm guessing they are $$, but always had a dream to maybe dual purpose the unit in a self made 'tool grinder' type machine.

Re the rotary stone, what sort of abrasive type & grit progression do you recommend on chrome?

Can you re-dress the stone mid-way a surfacing operation & somehow maintain the reference ID datum? Or you mean once set up, its put to work until completion of the grinding job?

Do you prescribe a typical criss-cross hatching pattern after the grinding with separate tooling/procedure or is there some trick to replicating with the Thermac & lathe compound motion?

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #123 on: December 29, 2014, 08:30:48 PM »
Jim, don't you grind on a "real" cylindrical grinder? On the lathe, I'm going to assume you're using a taper attachment, and not feeding with the compound? Setting the compound at oh 5.74° to get .0002" on diameter with .001" feed on the compound? I can't ever imagine feeding my old Clausing with the compound for grinding, or that Super 11 is a very nice lathe.

Greg

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #124 on: December 29, 2014, 10:21:54 PM »
- A Themac tool post grinder, turning at 20,000 RPM, is mounted to the compound to grind the cylinder's ID taper.
- Since the ID of the collet is much smaller then the ID of the cylinder, the grinding stone's RPM is raised to 40,000. I prefer to use a Themac tool post grinder because it is the only tool post grinder that allows precise centering of the grinding stone's center, with its unique rotating mounting of the spindle.
Jim Allen

Fascinating. Thanks again. You just answered my next question about tool post grinder. I guess its safe to say a jerry rigged die grinder would have insufficient accuracy, bearing/runout etc. attempting this level work? Would you mind telling me your model number or recommendation for ~14" swing lathe. I'm guessing they are $$, but always had a dream to maybe dual purpose the unit in a self made 'tool grinder' type machine.

Re the rotary stone, what sort of abrasive type & grit progression do you recommend on chrome?

Can you re-dress the stone mid-way a surfacing operation & somehow maintain the reference ID datum? Or you mean once set up, its put to work until completion of the grinding job?

Do you prescribe a typical criss-cross hatching pattern after the grinding with separate tooling/procedure or is there some trick to replicating with the Thermac & lathe compound motion?

My tool post grinder is a Model J-45 with a 2025 spindle. It is intended for 12" to 14" swing lathes. All the tools in my shop have been modified to give better performance. The grinder has a custom, hardened & ground base, that allows it to face grind or circumference grind pieces. The diamond dresser can be mounted to the lathes bed or in the lathes spindle. The 2025 spindle bearings have been replaced with Barden ABEC 7 bearings which are preloaded. I use a special permanent grease to prevent the spindle bearings from overheating. The grease is the same type that would be used in any quality surface grinder which has a permantely lubricated Pope type spindle..  I make the stones, which are mounted on tapered mandrels of different lengths, from scrape surface grinding wheels. For example, the ID of the engine's cylinder is 1.125". I drill a 1/4" hole & cut with a band saw, 1/2" or 3/4" wide, 100 grit aluminum oxide wheels which are dressed round after mounting. The size of the dressed wheels are approximately 1.000" to 1.100". I use a sulfur based grinding oil, Sunnen #MB 30-5, which has been used to previously grind chrome. In the photo notice that the lathes bed is completely covered. The oil is caught in a basin below the lathe's bed to be used again & again & again. Never use new grinding oil to finish grind hard industrial chrome. No dressing of the stone will be necessary to finish many pieces. The typical amount of chrome to be removed will be less than .0005" per side. To make all the cylinders being ground a particular size, a tapered hardened steel gauge is used to measure the ID. It's depth in the cylinder determines what size is being ground. Notice the .00005" waterproof, jeweled movement, indicators that tell exactly where the carriage, cross slide or compound are & how far they are being moved.

No cross hatch pattern is used in an ABC or an AAC type engine because there is no piston ring to be seated. ABC means an aluminum crankcase with a brass cylinder that is chrome plated. AAC means an
aluminum crankcase with an aluminum cylinder that is chrome plated. In ringed engines the cross hatch pattern is important not only for helping to seat the piston ring, it also determines how the piston ring is going to react as the piston moves up & down. If the pattern is to flat, it can cause the piston ring to flutter as the piston moves up & down. If the pattern is to steep, it can cause the ring to want to rotate as the piston moves up & down.

Note: I use the Themac tool post grinder with a custom mount on my Super Tech OD, ID grinder. The reason is, the grinding of small ID holes must be done at very high spindle speeds. Is there an ID grinding attachment for an OD, ID grinder which can rotate at 42,000 RPM?

Jim Allen
« Last Edit: December 30, 2014, 12:33:34 AM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #125 on: December 29, 2014, 10:40:46 PM »
Jim, don't you grind on a "real" cylindrical grinder? On the lathe, I'm going to assume you're using a taper attachment, and not feeding with the compound? Setting the compound at oh 5.74° to get .0002" on diameter with .001" feed on the compound? I can't ever imagine feeding my old Clausing with the compound for grinding, or that Super 11 is a very nice lathe.

Greg

Greg,

No taper attachment that I know of would be able to grind a precise taper in the cylinders ID if you're using a lathe for this job. All of the cylinders shown in the posted photos were ground using the Super 11 lathes compound. However the compound & the cross slides ways were ground to give a very smooth movement. Setting of the compounds angle is done with the "taper masters" as previously explained. The .00005" indicators mounted on the carriage, cross slide & the compound tell me where these thing are & if they have moved from where they were set. I learned a long time ago that INDICATORS DO NOT LIE.

As a matter of fact I have done OD, ID grinding on a 13" Clausing Glochester tool room lathe & a 14" G4002, Chinese iron, Grizzly lathe with the same Themac tool post grinder shown.

Jim Allen

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #126 on: December 30, 2014, 01:26:48 AM »
OK. I didn't think such precision grinding was possible with the compound. I don't know if my lathe would be capable, but I'll give it a try as soon as I get my Dumore reassembled. Fortunately, most of my grinding needs will be straight.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #127 on: December 30, 2014, 02:09:14 AM »
Here's another photo of a cylinder that just came off the lathe. Before you begin, use an indicator to see how much play there is in the gibs as you move the cross slide & the compound. Apply some force with your hand as you move each part. Any looseness will allow the vibrations from the grinder to be transmitted to the compound, to the cross slide & then to the carriage. Bad bearings in the spindle or motor cannot be tolerated. The flat belts used on the pulleys & the pulleys themselves must be in good shape. When the grinder is mounted & running, a .00005" indicator's needle will be stationary if there are no vibration problems. If the indicator needle in dancing, it will be impossible to grind to a specific dimension.

Hope this works for you. Making sure that everything is absolutely rigid is one key as well as the mechanical correctness of the grinder.

JA

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #128 on: December 31, 2014, 01:09:50 PM »
Jim, don't you grind on a "real" cylindrical grinder? On the lathe, I'm going to assume you're using a taper attachment, and not feeding with the compound? Setting the compound at oh 5.74° to get .0002" on diameter with .001" feed on the compound? I can't ever imagine feeding my old Clausing with the compound for grinding, or that Super 11 is a very nice lathe.

Greg

Greg,

I do have a "real" cylindrical OD, ID grinder. I find it is easier & quicker to set up the lathe's compound for small ID, short length pieces where small quantities are needed . I have a highly modified taper attachment which remains permanently mounted that is primarily used for machining tapered tuned pipe sections. The lathes custom cooling system is made of fully adjustable stainless steel pipes & uses only Mobilmet Omicron cutting oil; never any type of water soluble coolant. The four way hardened & ground tool holder is also custom made & it can be easily moved to the taper attachment. A special custom designed high pressure lubricating gun uses way lube to lubricate the carriage, cross feed & compound ways. Notice the additional custom made felt way wipes added to the carriage, the cross feed & the taper attachment ways to keep dirt out.

Jim Allen

Offline Roger B

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #129 on: January 06, 2015, 08:23:47 PM »
Thank you once again for the incredible amount of information you are posting  :praise2: One of my next projects will require some fine grinding and you have given me a good number of hints and tips  :ThumbsUp:
Best regards

Roger

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #130 on: January 08, 2015, 02:21:33 AM »
OK. I didn't think such precision grinding was possible with the compound. I don't know if my lathe would be capable, but I'll give it a try as soon as I get my Dumore reassembled. Fortunately, most of my grinding needs will be straight.
I was going to ask a similar question but will pose in a different way. I always assumed the compound would be set to some nominal, shallow angle so a small incremental feed would translate into a teeny-er amount of stock removal at the grinder wheel. For example, if compound angle = 15 deg, Sin(15)=0.259, so a 0.001" compound dial feed = 0.000259"on the work piece? Is that the concept?

But maybe we are talking about another issue in terms of the whole carriage movement against the lathe bed, or in this case, an angle/taper following type attachment?


> I drill a 1/4" hole & cut with a band saw, 1/2" or 3/4" wide, 100 grit aluminum oxide wheels which are dressed round after mounting

What kinds of tools are required to make holes in AO wheels like this? Do you then bond in a steel axle/mandrel before the final shaping & dressing? I had no idea this was custom wheel making even possible.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #131 on: January 08, 2015, 02:58:30 PM »
OK. I didn't think such precision grinding was possible with the compound. I don't know if my lathe would be capable, but I'll give it a try as soon as I get my Dumore reassembled. Fortunately, most of my grinding needs will be straight.
I was going to ask a similar question but will pose in a different way. I always assumed the compound would be set to some nominal, shallow angle so a small incremental feed would translate into a teeny-er amount of stock removal at the grinder wheel. For example, if compound angle = 15 deg, Sin(15)=0.259, so a 0.001" compound dial feed = 0.000259"on the work piece? Is that the concept?

But maybe we are talking about another issue in terms of the whole carriage movement against the lathe bed, or in this case, an angle/taper following type attachment?


> I drill a 1/4" hole & cut with a band saw, 1/2" or 3/4" wide, 100 grit aluminum oxide wheels which are dressed round after mounting

What kinds of tools are required to make holes in AO wheels like this? Do you then bond in a steel axle/mandrel before the final shaping & dressing? I had no idea this was custom wheel making even possible.

I think we are confusing each other with two different processes. If you are going to grind a straight shaft of any length, it should be mounted between two dead centers. Using two dead centers can only be done in the OD,ID, cylindrical grinder. However, when using the lathe, it can have one dead center which would be mounted in the lathe's tail stock. Before grinding any shaft in the lathe, that needs to have the same diameter on both ends, will require the tail stock's axis to be centered on the spindle's axis. This also applies to machining long straight shafts, which are not tapered. In fact, once I have centered the tail stock's axis to the spindle's axis, I NEVER MOVE THE TAIL STOCK TO CUT ANYTHING TAPERED! I use the taper attachment or the compound. The reason I do this is because sometimes I want to use 00 center drills mounted in the tail stock's drill chuck. Any tail stock misalignment will immediately break very small center drills & drills, especially when they are made of carbide.

A sample shaft, mounted between centers, makes it possible, once the dimension is the same on both ends, to center the tail stock's center to the lathe spindle's center. Once the tail stock is adjusted it should not be moved, even if the lathe's tail stock is ridding on a "V" way. The same process is done in the OD,ID grinder by adjusting the table's angle to give an equal dimension on both ends of the sample shaft. Carbide tipped centers cost more but last much longer than high speed steel centers. A quality high pressure lubricant such as CMD extreme pressure lube #3 should always be used with the dead centers.

No special tools are required to make small size grinding wheels. Any high speed steel drill will make many holes in any type of aluminum oxide wheel. Regrind the cutting flutes when they become to dull. Of course the drill will eventually become garbage. The wheels are rough cut using a course tooth band saw blade. Again, many pieces can be cut & the band saw blade will become garbage. You can make or purchase heavy paper pieces to glue, with rubber cement, on to both sides of the wheels. Clamp the stones to the mandrels shaft with machined steel washers, but never directly on the stone's surface!

Jim Allen
« Last Edit: January 08, 2015, 06:18:46 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #132 on: January 10, 2015, 02:25:29 PM »
I would like to share continuing developments concerning the building of very high speed bottom end roller assemblies that would be used in miniature very high performance two cycle engines. Retainers of this design type have been successfully used in engine's operating in the 30,000+ RPM range.

The precision machined retainers shown in the photos are the result of in depth designing & testing. The unique mechanical design (two rollers in each window instead of one) gives a retainer which has a very high load carrying ability, with no loss of limiting RPM, compared to a stock retainer. This happens because the two roller window design increases the standard roller count of 10 rollers, for the retainer's size pictured, to 16 rollers. There is no problem with rubbing friction even though two rollers in each window are in direct line contact with each other. Heat that is normally associated with roller assemblies is a result of the friction caused by roller skewing & roller skidding. The precision machined roller cages shown in the photos totally eliminate roller skewing because the rollers are guided along their center lines from end to end. This type of roller guidance is not possible with any type of snap in type roller cage design! Roller skidding is also greatly reduced because the retainer has very low mass & therefore very low inertia. The metallurgy used is a martensitic, precipitation aging, cobalt strengthened, 18% nickel maraging steel. With a simple heat treatment of 900* F for 6 hours, the C-350 maraging steel reaches an ultimate tensile of 350,000 psi at Rc 60. Some of the special characteristics of this steel would be it's high toughness, ductility, impact, compressive (388,000 psi) & fatigue strengths. The steel is resistance to crack propagation, is easily machined, has minimal distortion, predictable shrinkage & is free of decarburization during heat treatment.

Typical applications for maraging steels which began to appear in the 1960's are guided missile & rocket motor cases, wind tunnel models, recoil springs, landing gear components, high performance shafting, gears & fasteners. Prototype retainers are machined with the modified Brown & Sharpe #1 dividing head shown in the last photos. Fixtures, similar to the type shown, are directly mounted to the Brown & Sharpe's #5 taper dead center. The tapered dead center has been modified with a draw bar & is concentric within .0002".

Jim Allen
« Last Edit: January 10, 2015, 02:35:06 PM by strictlybusiness1 »

Offline Niels Abildgaard

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #133 on: January 10, 2015, 04:42:14 PM »
Hello Jim
It is a pleasure to be on Your guided tour
Do You use some kind of protective atmosphere during heating the maraging steel?

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #134 on: January 10, 2015, 04:57:52 PM »
Hello Jim
It is a pleasure to be on Your guided tour
Do You use some kind of protective atmosphere during heating the maraging steel?

No Niels. Any heat treating furnace that can hold the temperature, 900* F, + or - 5* F  for 6 hours will work. If the alloy was heat treated at this temperature for 20 hours it's tensile strength would approach 360,000 psi. The 6 hour treatment gives 320,000 psi at 400* F. & 300,000 psi at 700* F. After heat treating cool in air to room temperature.

The pie shaped material left in between each double roller window, at the center line of the rollers, is only .027" thick. Notice on the partial print that the pie shaped piece must become thinner as it moves towards the center & wider as it moves towards the retainer's OD.  It remains straight without distortion during heat treating. The retainers are always guided in the connecting rod's ID, never on the crank pins OD.

JA
« Last Edit: January 10, 2015, 05:14:57 PM by strictlybusiness1 »

 

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