Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129719 times)

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #465 on: May 29, 2020, 11:50:35 AM »
Thank you very much for all the information you have shared here Jim - much appreciated  :NotWorthy:  and I do hope that will enjoy what ever you choose to do with the time you have left  :cheers:

Best wishes

Per

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #466 on: May 29, 2020, 01:17:21 PM »
+1

Hey James,
For quite a while now Christian Lucas and I have been taking you work international. We show people your genius. Have a look. They ( the Germans) are there taking about IC speed plane engines. Of course you know very little about this.  :noidea:


LOL

http://www.rc-network.de/forum/showthread.php/782193-Mehr-Speed?p=5032516&viewfull=1#post5032516


BTW mom just turned 81 and dad 79 still motoring autonomously . Apparently you guys have taken pretty good care of yourselves . I can only pray to be so blessed.

Thanks for all you do.
Hubert,
« Last Edit: May 29, 2020, 01:33:34 PM by DRT »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #467 on: June 02, 2020, 06:09:05 PM »
 
James,
I know you have the articulated drive shafts. I have not seen how you are using the wire drives. Have you built a wire ferrule? I've seen  on Hydroworld.de post facto mill collets to hold 5mm wire for very high torque on the motor end. What do you have? What are your suggestions? I think I would like a wire or straight shaft for 1/8th. Scale SAW. I'd rather have some like some like yours . Is it possible in 3 pieces? To build some that squeeze a smooth 8 mm motor shaft at one end and then the 5mm or whatever size wire at the other. What material how to make the tapers etc.

Thank you,
Hubert
« Last Edit: June 02, 2020, 06:34:13 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #468 on: June 03, 2020, 12:45:06 PM »
Hugh, 

Many things have changed since ED & I used wire drives back in the 1980's. The collets we used operated at approximately 7 HP & 30,000 RPM. I posted some photos of these. All the parts were made of AISI-01 tool steel. The split collets were hardened to a spring temper. The collet seats were full hard 01 steel. They typically had .0002" total indicator runout 1.000" from the collets nose. They lasted indefinitely & they worked on both hard shafts & cables.  I cannot say if they would work at present day FE RPM's & torque. ER type collets are presently being used, some on gas boats & some on FE SAW boats. ER collets come in fractional sizes (.0156" increments) & typically have .0002" runout. They require smooth, round, straight, hard shafts at the motor end. Piano wire will not work! I am told that FE SAW boats operating in the 60,000+ RPM range are using a single piece coupler with saw slits. These things have a run out of less than .0002". I'll see if there are any photos to upload.

There is also a single piece coupler with slots that is supposed to have less than .0001" runout. It is shown on INTLwaters & it is preferred by some FE SAW boaters.

Jim Allen
« Last Edit: June 03, 2020, 01:06:05 PM by strictlybusiness1 »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #469 on: June 03, 2020, 02:46:05 PM »
Hugh, 

Many things have changed since ED & I used wire drives back in the 1980's. The collets we used operated at approximately 7 HP & 30,000 RPM. I posted some photos of these. All the parts were made of AISI-01 tool steel. The split collets were hardened to a spring temper. The collet seats were full hard 01 steel. They typically had .0002" total indicator runout 1.000" from the collets nose. They lasted indefinitely & they worked on both hard shafts & cables.  I cannot say if they would work at present day FE RPM's & torque. ER type collets are presently being used, some on gas boats & some on FE SAW boats. ER collets come in fractional sizes (.0156" increments) & typically have .0002" runout. They require smooth, round, straight, hard shafts at the motor end. Piano wire will not work! I am told that FE SAW boats operating in the 60,000+ RPM range are using a single piece coupler with saw slits. These things have a run out of less than .0002". I'll see if there are any photos to upload.

There is also a single piece coupler with slots that is supposed to have less than .0001" runout. It is shown on INTLwaters & it is preferred by some FE SAW boaters.

Jim Allen

Do you have a link to the IW post with the split collar @ .0001 runout?

Thanks
Hubert

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #470 on: June 03, 2020, 03:29:06 PM »
Hugh,

I can't find a link to the single piece coupler. The piece is not hardened & it is only split on both ends; not in the middle. Both holes sizes are drilled from one end, big diameter first. The motor shaft size & wire drive size holes should be a hard push fit. This is not a difficult piece to make. It could be hardened & ground if it was made of steel.

JA
« Last Edit: June 04, 2020, 01:05:53 AM by strictlybusiness1 »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #471 on: June 04, 2020, 05:31:00 PM »
Ok. I can see the piece and understand how to make it. But what I wonder about is its balance.


Thanks
Hugh
« Last Edit: June 04, 2020, 06:14:26 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #472 on: June 04, 2020, 10:18:40 PM »
Hugh,

I have been told by FE SAW boaters that this piece when made properly has the least amount of vibration. The double clamping screws on both ends give it a very high clamping force, especially if the wire used fits. Careful machining of the counterbores will be critical.

JA

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #473 on: June 06, 2020, 03:52:27 PM »
Understood.

Is there something better than loctite on the propshaft end of such powerful boats. Losing prop$ from Andy would not be cool. Could a split ferrule be made the same way. It seems possible but the counterbores and bores may be smaller than one would want to tap as its at the taper of the ferrule.

....and thank you.

Hugh
« Last Edit: June 06, 2020, 03:58:45 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #474 on: June 07, 2020, 08:05:15 PM »
The fastening of the propshaft to the wire drive shaft doesn't present a problem, if the wire drive is a ground shaft & it is a slight  press fit into the prop shaft. The wire drive shaft will be flared at the prop shafts threaded end. #648 Loctite is used as an adhesive. The cone point Bristol set screw that holds the drive dog to the prop shaft can also be used to help in holding the wire drive shaft in place. The cone point of the Bristol set screw & the taping drill should have the same angle. # 648 Loctite should be applied to these parts during assembly. I recommend four faceted carbide drills & carbide reamers to be used for this job.

Jim Allen

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #475 on: June 09, 2020, 03:02:55 PM »
Hi James,
 
Why Is a good piece of ASTM A228 (music wire) not good for the drive line? I also want a straight shaft and plan to push the motor all the way into the nose of the boat. An want a nice true shaft if the wire wont work. If i use the straight shaft what kind and how would you support it along its length? I want minimal drag. Maybe a hollow drive shaft?

1590 - 1760 MPa
@Diameter 6.35 mm   231000 - 255000 psi
@Diameter 0.250 in   
    1640 - 1820 MPa
@Diameter 5.26 mm   238000 - 264000 psi
@Diameter 0.207 in   
    1690 - 1860 MPa
@Diameter 4.50 mm   245000 - 270000 psi
@Diameter 0.177 in   
    1740 - 1920 MPa
@Diameter 3.81 mm   252000 - 278000 psi
@Diameter 0.150 in   
    1770 - 1950 MPa
@Diameter 3.56 mm   257000 - 283000 psi
@Diameter 0.140 in   
    1800 - 1990 MPa
@Diameter 3.18 mm   261000 - 289000 psi
@Diameter 0.125 in   

    1870 - 2070 MPa
@Diameter 2.54 mm   271000 - 300000 psi
@Diameter 0.100 in   
    1940 - 2150 MPa
@Diameter 2.00 mm   281000 - 312000 psi
@Diameter 0.0787 in   
    2020 - 2230 MPa
@Diameter 1.60 mm   293000 - 323000 psi
@Diameter 0.0630 in   
    2090 - 2310 MPa
@Diameter 1.30 mm   303000 - 335000 psi
@Diameter 0.0512 in   
    2170 - 2410 MPa
@Diameter 1.00 mm   315000 - 350000 psi
@Diameter 0.0394 in   
    2250 - 2490 MPa
@Diameter 0.810 mm   326000 - 361000 psi
@Diameter 0.0319 in   
    2350 - 2600 MPa
@Diameter 0.610 mm   341000 - 377000 psi
@Diameter 0.0240 in   
    2500 - 2760 MPa
@Diameter 0.400 mm   363000 - 400000 psi
@Diameter 0.0157 in   
    2600 - 2880 MPa
@Diameter 0.300 mm   377000 - 418000 psi
@Diameter 0.0118 in   
    2750 - 3040 MPa
@Diameter 0.200 mm   399000 - 441000 psi
@Diameter 0.00787 in   
    3030 - 3340 MPa
@Diameter 0.100 mm   439000 - 484000 psi
@Diameter 0.00394 in
   
Modulus of Elasticity    210 GPa   30500 ksi   
Poissons Ratio    0.313   0.313   Calculated
Shear Modulus    80.0 GPa   11600 ksi   
 
« Last Edit: June 09, 2020, 08:15:54 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #476 on: June 10, 2020, 02:11:29 AM »
Music wire is drawn, not ground, therefore, it is not straight. When Ed & I used music wire for drive shafts it had to be straightened. If the drive shaft is a ground shaft .093'' to .125" it could be bent slightly & supported at 3.0" intervals. The shaft supports were approximately 3/16" to 1/4" wide. They were soldered in the next telescoping size tubing by drilling a hole at the solder point. We did this same thing with shafts that were .1875" to .250". Very light weight #2 lubriplate marine grease (L0206-001) was used as a lubricant for both the solid shafts & cable shafts. Remember these drive shafts never exceeded 30,000 RPM. I have no idea what lubricant is used for a shaft operating at 60,000 RPM.

JA

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #477 on: June 10, 2020, 11:08:40 PM »
Hi James,
Thanks for more information. For the stuffing tube internal supports did you use bronze bushings? Do u have a stateside link for 3.125-4mm ground shafts I need at least a meter.

Thanks
Hubert

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #478 on: June 11, 2020, 05:57:26 PM »
In the early days we used plain hard drawn brass tubing. Later we used B-8 Bearium alloy for the bushings. The bushing pieces were machined with a 3/64" wall thickness. This gave a much greater area to contain the lubricating grease. The B-8 Bearium metal was also used in our struts. The angled water inlet in the bottom of the strut made the strut bushings last forever. Notice that the strut bushing is held in the strut housing with a 3-48 screw. Also notice the brass sleeve soldered at the cable, hard shaft joint. This piece not only reinforced this joint, it also made it impossible to lose the propeller shaft in the event of a cable failure because it's OD is bigger than the machined bushings ID.

Jim Allen

note: I have no information about hardened ground small diameter shafting except that I've been told it is available.

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #479 on: June 13, 2020, 06:12:12 PM »
Beautiful work. How did you and Ed attach the wires to the engines? I also would like to know did you grind the spring steel turn fin. I need  to make one for scale saw How did you manufacture it and how did you color the hardware? It's beautiful.

Regards
Hubert

 

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