Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 92902 times)

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #450 on: May 19, 2020, 06:14:38 PM »
  :happyreader:

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #451 on: May 20, 2020, 02:39:06 PM »
One more in overly complex two stroke designs with no advantage over a simple tuned pipe, crankcase scavenged engine.  Also, the pumped volume under the piston isn't enough to adequately scavenge the cylinder.  The design is similar to a recent infamous engine that never lived up to its claimed power.

Lohring Miller

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #452 on: May 21, 2020, 01:32:11 PM »
Thanks Lohring. What do you think James? Can the idea be perfected or expanded on? Two strokes have come along ways rc boat motors really have not from what you've shown many times on the boat forums. Just an idea. No one said it was supposed to make gobs of power or be better than something else. I don't know anything about it. I'm just sharing it with you as I do most things mechanical new to ME. I don't miss the boat forum discussions or the attitudes they create. For me its all learning for fun because my electric motors make more power and torque than any IC used in rc boating. I don't really care about it enuf to volley.

Hugh
« Last Edit: May 21, 2020, 01:38:49 PM by DRT »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #453 on: May 21, 2020, 04:27:23 PM »
Hi DRT, thanks for that explanation, itís great to know a little of where you fit in.

It is clear that some amazing work is being documented in this thread, and I normally just look on in awe (and silence).  But I am interested in why, when you were talking about identifying those standing wave frequencies in excell, you went to regression analysis instead of the Fast Fourier Transform function.  If it is a big enough data set, and that may of course be the problem, the FFT quickly identifies any natural frequencies in the data set.

Oh, and also, please add my vote to Admiral DK for your build thread on a simpler dynamometer for us mere mortals.

MJM460

Sorry I missed this......
Im not sure I follow you or remember the post you referenced. I use FFT quite often in THD measurements of my electrical machines. I'm very familiar with it but in looking at points U could derive a line of best fit without pulling out a scope and or additional recording equipment. . There must have been some misunderstanding as I hope no ones feel godly or ungodly about any of this stuff. No matter what anyone shows you were all still going to die at some point. ;) Ill have to consider a thread because my hands are full with development of my own dreams. Thread and forums in general are time consuming and really pull away from time that could be spent perfecting whatever it is you are working on. I also don't want to debate or argue at great depth about IC engine development dynos or things like that.Jim can tell you i've seen enough of that and have zero interest. People are free to do whatever they think works and interest them but I have made the switch and for me there is no reason to ever go back. What model engine maker does for me is let me rub shoulders with precision machinist and people such as yourself so I can continue to add to my knowledge base and skill set in the trade. Things learned from you.  I also get to admire great work. It doesn't have to be an electric motor to still be really cool. Maybe I look at a solenoid boxer thread for this site. I never really examined them to see if there's a better mousetrap. I'll consider it or possibly an electric motor build where the expert machinist here can help me make the construction light strong and effective. Technically it still is a "model engine". My post about TEDS sensors wasn't a critique more than a suggestion from the engineering profession about what the standard is today to gain experimental concurrence across the board of peers. I find it relevant as Lohring and Jim compare the effectiveness and limitations of the two styles. The inertial dynos mechanical integrity can be improved with the retention sleeve and Jim can have more accurate recording with a TEDS load cell because it will require him to calibrate it on an interval and record of that is kept in a virtual database somewhere the IEEE determines. It opens the door for more peer concurrence when making or stating performance gains and losses from a dyno. It helps to make sure we are on the same page with what we see with our experiments is allz.


Thanks for your time and patience :cheers:
Hugh
« Last Edit: May 21, 2020, 04:56:42 PM by DRT »

Offline MJM460

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #454 on: May 22, 2020, 02:14:10 PM »
Hi Hugh, I am with you on the time issue with forums.  I strictly limit which ones I follow, but still can get carried away at times.  Probably a sign that this forum in particular, is a good fit with my interests.

I was interested in why you went for the regression analysis, not due to any expertise on my part, just a vague knowledge of FFT from student days, noticing it available in Excel, and trying it out on a data set I happened to have amongst some other documentation, to see what I could learn.  The natural frequencies stood right out as you would probably expect.  Thatís about it.  So interested in why you used a different method of analysis.  Definitely no interest in an argument.  And not wishing to waste your time.

I would like to make a brake for my little engines eventually, so am always on the lookout for the necessary ideas on how to make the necessary measurements.  I have rpm mostly sorted, but any pointers on measuring a force on the torque arm you are willing to share would be most appreciated.  I have been interested to read about the inertial brakes, but for my engines, I suspect the conventional types are more appropriate.  I still have a few areas to work on to get to a complete design.  I am leaning towards a DC motor or perhaps eddy current principle.

I will be very keen to follow when you get around to a thread on your own developments.   They do sound most interesting based on what I have read so far.  I am definitely enjoying Jimís amazing work on this thread, so donít wish to hijack that either.

MJM460
The more I learn, the more I find that I still have to learn!

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #455 on: May 22, 2020, 05:14:11 PM »
Thanks Lohring. What do you think James? Can the idea be perfected or expanded on? Two strokes have come along ways rc boat motors really have not from what you've shown many times on the boat forums. Just an idea. No one said it was supposed to make gobs of power or be better than something else. I don't know anything about it. I'm just sharing it with you as I do most things mechanical new to ME. I don't miss the boat forum discussions or the attitudes they create. For me its all learning for fun because my electric motors make more power and torque than any IC used in rc boating. I don't really care about it enuf to volley.

Hugh

I must agree with Lohring when you consider the mechanical simplicity of already proven tuned pipe, crankcase scavenged two cycle engines which use various types of induction systems. There is still a great deal of work to be done with tuned pipe systems, a technology that requires no moving mechanical parts to increase the engines HP. Advances in metallurgy continue to help increase two cycle engine performance & mechanical reliability. I do not know & I do not care about electric motors at this point in my two cycle engine development. As far as the various types of brakes are concerned, there is nothing simpler in design as a water brake.

The main problem with all of the smaller miniature braking devices is there inability to accurately measure small amounts of torque. Not trying to, :stir: the pot, just my opinion.

Jim Allen
« Last Edit: May 22, 2020, 07:45:05 PM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #456 on: May 23, 2020, 07:41:17 PM »
Another clever connecting rod idea that would be difficult to engineer for high speed applications.

JA

Offline lohring

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #457 on: May 24, 2020, 02:52:54 AM »
However, the flash steam guys use the Scotch yoke as a pump drive.  The rpm is a lot lower with around a 5 to 1 reduction from engine rpm.

Lohring Miller


Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #458 on: May 24, 2020, 04:03:24 PM »
Thanks Lohring. What do you think James? Can the idea be perfected or expanded on? Two strokes have come along ways rc boat motors really have not from what you've shown many times on the boat forums. Just an idea. No one said it was supposed to make gobs of power or be better than something else. I don't know anything about it. I'm just sharing it with you as I do most things mechanical new to ME. I don't miss the boat forum discussions or the attitudes they create. For me its all learning for fun because my electric motors make more power and torque than any IC used in rc boating. I don't really care about it enuf to volley.

Hugh

I must agree with Lohring when you consider the mechanical simplicity of already proven tuned pipe, crankcase scavenged two cycle engines which use various types of induction systems. There is still a great deal of work to be done with tuned pipe systems, a technology that requires no moving mechanical parts to increase the engines HP. Advances in metallurgy continue to help increase two cycle engine performance & mechanical reliability. I do not know & I do not care about electric motors at this point in my two cycle engine development. As far as the various types of brakes are concerned, there is nothing simpler in design as a water brake.

The main problem with all of the smaller miniature braking devices is there inability to accurately measure small amounts of torque. Not trying to, :stir: the pot, just my opinion.

Jim Allen

I have to disagree Jim . The water brake you inherited and improved from Ed Kalfus is not simple to design. Maybe for you it is.  How many "you's" are there in hobby Today? How many high performance custom .90 engines are you seeing designed. No different that the other stuff u do it wont be done by many people. An brushless motor turned generator using load resistors or just fets (bridge) across UHV to short them at a duty cycle will provide plenty brake and can withstand over 30,000 no problem.  You will see hobbyist use this before a custom built water brake. Beautiful yes, but doable and eazy for 95% of the hobbyist NO! It also has the dual function that as long as the EQ is provided it can also calculate the inertial acceleration of the rotor. There is certainly a brushless dc "generator" that can handle your needs.



U see this 448.8 gram motor will run at over 35,000 and generate 1400 oz-in of torque. I added 2 full cents of copper. Measuring torque is fine because a rather small amount of current can always be measured with a scope or dedicated current measuring device on an electric motor and easily converted to torque figures using the torque constant of the motor. Which is found generally by 1/Kv. So torque generally equals the (Tq)x(Amperage)x(winding factor of the motor). There is no question that constructing a water brake with real time data logging much more difficult than strapping the IC engine to an electric generator. Additionally u could use a on axis TEDS reactionary torque device will tell you all you need to know about the torque and that sensor will be as accurate as anything the IEEE accepts because if its TEDS it has to be. You know full well many aren't capable of building a water brake. Why else would you post it. :Lol:


ÖÖ..and well the pots been stirred. You know "fast electric boat"s are running at over 200 mph now. 

Thanks for your time and patience.
Hubert
« Last Edit: May 25, 2020, 04:47:58 PM by DRT »

Offline dieselpilot

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #459 on: May 24, 2020, 05:31:58 PM »
Are you calculating actual torque from current? are you able to calibrate it? how long can you run it with air cooling? I understand only relative measurements really matter, like any other dyno. I've been sitting on a generator dyno project for years, mostly because it's for fun. I do have a rotary torque sensor, but skipping it would just make things easier.

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #460 on: May 24, 2020, 09:15:21 PM »
If you would like to use an ft arm mount a cradled generator to the arm and load cell when you brake the motor it will pull the arm. You can check the accuracy within reason of any current measurement device with a current clamp from a scope a DMM etc. Which is adequate in current reading. The rest is basically math formulations. The torque constant of the BLDC (Kt) is just that...a constant you can multiply by the current draw. You need to factor in the winding factor of the electrical machine and it efficiency.  The extra copper helps with heat mitigation but I am working on cryogenic cooling system as well as ferro fluid cooling directly into the air gap which uses a passive action by way of magnetic curie function. The initial result so far has brought cooling to -29 degrees Celsius. Any dyno will generate heat. I imagine Jim waterbrake get warm even with the water there it there isnt any significant volume id imagine it could boil. Maybe not. The ft. arm wont change the basic function so there will be an inherent check between the arm load cell reading and the the torque constant and current. This is no comparison or (better) thing it's just another option thing for people who cannot design and build a hydraulic dyno. That's many hobbyist.



BTW A reactionary torque sensor does not fully rotate. They are different. I'm not talking about the rotational type that mount between the prime mover and the braking generator. The motor itself would mount to the reactionary sensor on axis but its connection to the load generator would be virtually unchanged on the business end. A flywheel or any prop will require that "reaction" to get going.  This is already more than what I want to do In Jims thread. If you would like you can email me personally and we can go further with the discussion.I have much more but lets not get to far away from the IC work being shown here. James is like a second father to me so I want to be courteous as you can understand. He may not want this here. Make no mistakes there is much more for me to learn here than there is to teach. For a small IC engine a high pwered 1/4 scale servo can be the reactionary sensor. It has a holding torque that correlates to a certain amperage. You just need to calibrate weights to amperage using calibration weights. One you derive the regression eq the torque can be calculated quite easily.  That Eq can be placed in a MCU registry or excel cell . They wont care. The rpm can be derived through the BLDC's generated bemf frequency observed on a scope or an optical shudder and trigger wheel at the coupling of the prime mover and generator. No issue.

TEDS = Transducer Electronic Data Sheet

https://standards.ieee.org/content/dam/ieee-standards/standards/web/documents/tutorials/teds.pdf  :wine1:
 
Thank you for you understanding
Hubert

PS
James check to see if your transducer is TEDS compatible. If you need data acquisition email me details about the sensors you have and what you want. I can put it together and soon you will have all the wonderful graphs and visual representation. Plus it will be all recordable so u wont be taking notes by hand. In the last attachment is Christians brake. You see there is a solid cylinder of copper on a threaded rod that can be increasingly inserted into the outrunners bell . The solid copper would be the same as shorting the phases of an equivalent motor so you basically enable the EMF braking of load generator. This solid cylindrical slug of copper could also be water cooled or by some other medium. This work just like the steady state dyno paper I sent you years ago with the hard drive platters and magnets for the brake . I guess Lohring let building it go but this one he could do very easily. Its simply a large outrunner bell coupled to your IC engine then the cylindrical copper slug that you can insert in the bell incrementally or full adjustable loading. You also have the inertial with the rotor bell weight and diameter acceleration if you do the math and store it in a registry. THAT bell could be made from CF  :stickpoke:

 
« Last Edit: May 25, 2020, 05:06:26 PM by DRT »

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #461 on: May 25, 2020, 09:46:04 PM »
A close up of the last attachment. You should be able to visualize the IC as the prime mover versus the BLDC outrunner. Do you see the copper slug. You could make this brake versus using an OEM bldc because it is just a can with magnets alternating N - S - N - S....... and the slug. You can use your genius to figure out how to cool the copper slug. I dont think it too difficult. With the Schulze controller of course all the data taken in this photo was inherently data logged by the controller. You will build the acquisition for the nitro using excel sensors an cell math or purchase acquisition equipment. Tyler knows this style shown in TK's test stand thread and the others outside the one from his work belong to Christians associates in Germany he built many of them. If Im not mistaken The one shown belongs to an RC boater that races the 2.33 meter electric cats!

TTYL
Hubert,

@ James i see your concerns with minimal torque. Id think it negligible if you are comparing all your motors on the same stand. With the BLDC generator design the friction (amperage) of the drive train can be factored in easily. I f you simply remove the IC engine and run the BLDC motor with the entire drive train in tact. An inverter with data logging can compare that amperage draw from that of the BLDC motor with nothing coupled to it. Basically the idle current. This difference can now be accounted for. In SAW you look for all out RPM and u need torque to deliver it from a standstill quickly. I don't think these minimal torque figures come into play so much for SAW. Id think you need significant increases to go to the next level of speed.

Just my opinion. Doesn't mean much.
« Last Edit: May 26, 2020, 12:53:47 PM by DRT »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #462 on: May 26, 2020, 03:48:43 PM »
Hugh,

Very interesting stuff, but not for me at this point . At 80 years of age it is a project to spend only one day at the lake. I have given away my new 16 ft retrieve boat & its trailer. I have given my boats & engines to my grandson who is studying to be a nuclear engineer for the US Navy. He attends Texas A&M, Galveston, with a full scholarship & will graduate with honors this fall. I hope some younger model engine builders will use what has been accomplished through many hours of testing & building miniature high performance two cycle engines.

Jim Allen

Offline DRT

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #463 on: May 28, 2020, 03:01:26 PM »
WE WILL!
I'm tooling up now, and well I thank the lord for you good health and appearance. I believe you have much more time than you think. Eat right and keep the weight off and you'll be good for many more years pop! Ur active so don't get too complacent and start sitting around at just the stand. When u really want to go. Call me and ill come right up to VA. I got the boat and the truck to pull it in style. Its no issue if you need someone with common sense to help. Beside I plan to make a visit to EC when that open up again. I'm coming for DON 1/8 scale u tell him Hi for me coz I'm still not back on IW!


TTYL
Hubert

Offline MJM460

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #464 on: May 29, 2020, 10:52:42 AM »
Hi Jim, itís a big decision to draw a line under the project you have worked on for so long.  But itís a wise man who is able to call it in his own time.

I have been fascinated and amazed to read about what you have done, and admire the skill and dedication you have shown.  I feel privileged to have been allowed a glimpse into your workshop.

I do hope your grandson appreciates what he has been given, and while family and career may have to take priority for a while, I do hope he is able participate eventually. 

I join in the feeling that you have many more days at the lake ahead of you, and will get plenty of enjoyment from seeing others carry on the game.  I am also sure that you will find many other interesting things to do between the days at the lake. 

 MJM460



The more I learn, the more I find that I still have to learn!