newbostonconst - most engineers I know make valiant efforts to control all of the variables so that they can isolate the effect of the variable they are trying to assess. So, if you want to assess the effect of rpm on power, holding torque at a constant value is a big help. So if we successfully hold torque constant, and increase rpm, won't the power also increase until maximum power is attained? I agree with you that power normally decreases as rpm increases beyond the rpm of the maximum power point.

sailawayrb said "High RPM is for high power…" You said:

"The most obvious one is "High RPM is for High Power" - That is wrong, engines will produce their most power at a certain RPM but that does not have to be at their highest RPM."

sailawayrb said "High RPM" but you said "highest rpm" not sailawayrb. Then you began chastising her for something she never said. Wikipedia says: "A straw man is a common reference argument and is an informal fallacy based on false representation of an opponent's argument." Did you purposely do that?

Nevertheless., if most spark ignition engines increase in power as rpm increases over most of their operating speed range, how can you say it is incorrect to say that "High RPM is for high power"?

Let's set up an example. Most gasoline fueled, spark ignition, passenger car engines reach maximum power at 5,000 rpm (old V8s; 6,000+ rpm for new I4s) or greater. I chose these engines because I believe these have the higher production numbers than any other engine types in the US. My sense is that these engines have a red line within maybe 1500 rpm or less, of their max power rpm. So, for most of their operating range, their power increases with increasing rpm until they reach maximum power at 5,000 rpm or greater. I don't know of any popular (high sales) passenger cars with a red line above 8,000 rpm, so the majority of their operating range is in the segment where power increases with increasing rpm.

So, if I'm correct, would you dispute the proposition that over most of the operating range of typical passenger car engines, power increases as rpm increases? Most engineers I've worked with don't consider a machine (car, boat, generator, etc.) well designed if it includes an engine that operates above it's peak power rpm for more than a small fraction of its operating life (drag racers excepted). If you agree with that, how is sailayayrb's statement about power as a function of rpm incorrect? If you disagree, can you educate me on which common machines are designed to be powered by engines that normally operate at crankshaft speeds above their peak power rpm?

Pidg, you are correct in what you wrote.

The Lister engine tops out at 650 to 1500, as you mentioned. To most people 650 to 1500 is not "High RPM", most cars idle in that range.

“High RPM” is a relative term. What I think is high RPM is not what you might think is high rpm.

If one was to think that you could change the pulley on a Lister to make it spin faster to create more power on a genset you just bought; it would likely make less power because that would put the engine out of its power band. Thus “High RPM” is not always for high power.

Thanks for your great reply.

Wow Pidg, my sincere thank you for clearing all that stuff up…and excellent post!

I hope we can also all agree that you never get more power or less power by changing pulleys… Changing pulleys will only change the speed and torque…and in such a way that the power always remains exactly the same. When you drive an output pulley that is half the pitch diameter of the input pulley, you get twice the speed of the input pulley, half the torque of the input pulley, and transfer exactly the same power...except for a minuscule power loss resulting from pulley/belt friction. Power (HP) = Torque (In-Lbs) x Speed (RPM) / 63,025. We have a pulley calculator on our website:

Borst Pulley System Design Software

The Lister engine I referred to is operated at a constant speed. 650 RPM is most common speed, but I think some operate as high as 1000 RPM with more robust flywheel designs. Please also keep in mind that these are open flywheel engines and it is often the flywheel design that limits the maximum engine speed.

When I am wrong, I always admit it, apologize, and do my best to make it right. Case in point…and I spent the better part of a weekend working out why my original ICF effective R-value premise, physics and math were wrong…and then presented the correct premise, physics and math:

ICF Effective R-value Discussion

However, I will never apologize when I am absolutely right to someone who is absolutely wrong just because they have a fragile ego and always fly into a rabid rage every time they are proven wrong.

In a 120/240 generator which most people use, the RPM of the generator has to stay constant. Thus if you change the pulley the engine will have to operate at a different RPM thus will be producing more or less power then it did before the pulley change. Thus like I have been saying if you change the pulley the wrong way and make the engine spin to fast or to slow you will be producing less power out of your genset....nice try....but wrong again.

You must be operating a DC generator.....

What is a more robust flywheel design?

No, I am afraid you are wrong again. Pulley systems don’t change power. Pulley systems only change torque and RPM, and in such a way that power transfer always remains constant.

No, we operate an AC generator...specifically an ST5 generator head sourced from China. These 6 HP Lister engines operate at a constant speed of 650 RPM and the pulley system changes the speed at the generator to 1800 RPM (i.e., the synchronous speed required to generate 60 Hz 120/240 VAC using a 4 pole ST5 generator). The power at the engine shaft and at the generator shaft is exactly the same (6 HP). Engine and generator photos may be found here:

Borst Lister Engine Photos

A more robust flywheel design is one that can operate at a higher RPM before the centrifugal tension or hoop tension stress exceeds the material stress limit of the flywheel causing it to fail in an exciting and dangerous manner. For example, using steel in lieu of cast iron would result in a more robust flywheel design allowing higher RPM operation.

It is also true that Lister engines can be purchased with a more robust flywheel design that allows operation at a higher constant speed (e.g., 1000 RPM) which results in higher power (e.g., 10 HP). A different pulley design still results in a generator speed of 1800 RPM. Nevertheless, the power at the engine shaft and at the generator shaft is exactly the same (e.g., 10 HP).

So you said your generator runs at 1800 and engine runs at 650 then
1800/650=2.769
2.769 is the pulley ratio you are using.
so lets look at what happens when you change your pulley ratio which you will see in the end increases or decreases your engine running RPM.

First lets change the ratio to 3.6. You can increase the the size of the engine pulley or decrease the generator pulley it doesn't matter. You could also change both pulley sizes.

So the 1800 generator rpm needs to stay constant because we are always producing 120/240 60hz outlet power.

1800/x=3.6 so solving for x that would give you 500 engine rpm.
x=500
1800/500=3.6
1800 is your generator RPM
500 is your engine RPM
3.6 is your pulley ratio

Now if you change the pulleys the other way so your pulley ratio is 1.8 by either decreasing the engine pulley size or increasing the generator pulley size.

1800/x=1.8 so solving for x that would give you 1000 engine rpm.
x=1000
1800/1000=1.8
1800 is your generator RPM
1000 is your engine RPM
1.8 is your pulley ratio

You will be getting these three engine rpm's 500 650 and 1000 because you changed your pulley ratio. You are telling me that at those three RPM's the engine is going to produce the same power? Or you are saying that the generator will always produce the same power no matter what the engine power is.

In either case both instances are wrong. The genset will only generate the amount of power the engine is putting out, and the amount of power the engine is able to put out is is dependent on RPM. It will put out its peak power usually at one RPM and be lower at all other RPM's So changing your pulley ratio to make your engine turn faster then you peak power rpm will not create more power.

“1800/650=2.769”

Yes, that’s true and defines the pulley system drive ratio (i.e., defines the input/output pulley pitch diameters).

“So the 1800 generator rpm needs to stay constant because we are always producing 120/240 60hz outlet power.”

Yes, that’s true. In fact, the goal is to maintain exactly 1800 generator RPM even when the electrical load changes.

However, this also implies that the goal is to maintain exactly 650 engine RPM because we can’t change the pulley system drive ratio real time while our engine/generator is operating. So why do you think the drive ratio changes or needs to change and then go through all that math?

To compensate for electrical load changes, the engine mechanical governor decreases or increases the fuel flow to engine so as maintain a constant 650 engine RPM and therefore a constant 1800 generator RPM. So let’s say the electrical load increases because we start using our microwave oven. In this case the mechanical governor provides more fuel to the engine to maintain this constant 650 RPM speed. In this case, additional fuel provides additional BTUs that are converted to additional power to address the increased electrical load torque. This increased engine power results from increased engine torque because the engine is operating at a constant speed of 650 RPM and this increased engine power is precisely in accordance with the power/torque/RPM equation. This increased engine torque is also precisely the increased generator torque that resulted from the increased electrical load that resulted from using our microwave. Nevertheless, the power at the engine shaft and at the generator shaft is exactly the same, even if both are now higher than they were when we were not using our microwave.

Wow, I've been away for awhile, but it just keeps going. I hope no one comes here hoping for answers for radiant floor design with wood framing! To any mod out there, you are welcome to delete this thread, since it has gone totally off-topic, and just seems to be an argument over who is smarter, or who is stupider, I'm not sure which. Mrs. Borst my floor plan is almost finished, just making some slight modifications, but I will be in touch with you soon. Thank you again for your kindness.

https://www.geoexchange.org/forum/threads/infloor-heat-install.6454/

Picture of extruded plates w/pex, 8" on center.

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/House.htm#Press

Gary of Builditsolar doing a retrofit radiant on top of subfloor. Lots of DIY info at his website.

"Unlike you and Badger, I am not marketing or hawking anything."

I'm sorry but posting links to your software, that I'm sure cost lots of time and money, is a form of marketing. Any business person will try to get a ROI.

I'm willing to bet you have gotten some amount of business from people that try to use the software, then call to have questions answered. Oh turns out they are in your area and hire you to do a project.

I really don't care if that happens or not. I also don't care if Morgan has an unhappy vocal customer or two.

I am not here to buy anything from either party. I read to learn and while learning from a book smart engineer has value, I appreciate real hands on experience type of advice.

Chris

Chris, you are just another ASSociate of the crooked Morgan gang. BTW, Gary at Builditsolar endorses Borst and Borst endorses Builitsolar.

Newboston, you went out of your way to insult Borst and criticize them about not apologizing when wrong (when they are right…). So you have again been proven wrong on the subject you claim to be an expert and we are now waiting for you apologize to Borst.

No, this thread won’t be going away. I will be bumping it up the first of every month just to inform new forum members of the evil goings on here.

I am happy to see the OP is happy with Borst and not fooled by the crooked Morgan gang shenanigans.

Whatever, now you are the one calling names, I thought I was playing pretty nice.

Chris

I have to agree with Chris here. While I appreciate the sentiment and the support, please cease the name calling ICFBound. Everyone else is behaving better right now and I would like to see this continue.

Yes Chris, I can see how you would view my posting links to our software as marketing. However, I only post these links when they provide the answer or solution to the question or problem being posed by the OP. I think most people can see the difference between providing helpful information versus endlessly just hawking that Manual J analysis is the cure for world hunger and that they do it. Here’s the latest example of that even when this is not even needed:

Converting to Natural Gas from Oil

Providing free benefits to customers is also a pretty common business model these days (e.g., Facebook, Google, this forum, etc). Nevertheless, most of our business still comes from word mouth from previous customers and our other business associates. There is a huge DIY community and these folks most often just use our software for free and we hardly ever see any revenue from them. However, we are highly supportive of the DIY community and we are very happy to help them as best we can.

You are both right that was excessive on my part. I apologize and will try to restrain myself in future.

Thank you.

Posted By sailawayrb on 11 Apr 2015 10:57 AM
I think most people can see the difference between providing helpful information versus endlessly just hawking that Manual J analysis is the cure for world hunger and that they do it. Here’s the latest example of that even when this is not even needed:

Converting to Natural Gas from Oil

Wow, isn't that a great example of the truth!

Back when they all played nice!

sailawayrb Veteran Member Posts:1155 23 Jan 2013 05:17 PM Quote Reply Alert

"Badger and Dana have given you very good advice…you first need to do a proper building heat loss analysis and it will be problematic integrating these two very different styles of heating systems. Feel free to use the DIY calculators on our website, but my sense is that you would be much better served just to hire a knowledgeable/capable company in your area to sort this out for you."

Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!

Chris

I think most people can see the difference between providing helpful information versus endlessly just hawking that Manual J analysis is the cure for world hunger and that they do it. Here’s the latest example of that even when this is not even needed:

Are we to presume Borst Engineering does not work in an area governed by the IRC (International Residential Code) which requires equipment be sized specifically by ACCA Manual J or other approved (inspectors' discretion) methodology?

I know this thread has had its share of ire, but to suggest that it (man. J) is not needed unless aquainted with local codes (and inspectors) does not appear to be responsible advice. Since you seem to have a new fan with nearly 2 dozen posts that has taken that advice to heart and criticized the practice elsewhere (though it may well be required by law), you might wish to clarify your position.

Chris, I am not sure we ever played nice as I clearly recall being "badgered" from day one, but thank you none the less.

Joe, being an engineering company, we are not limited by the limitations of Manual J. We can accomplish a heat loss analysis using more modern and more accurate ASHRAE methods (or any other method we choose) and PE stamp it such that it could be approved in every State. In fact, we are not limited by IRC prescriptive code in general and we can totally depart from the code as required using engineering principals.

Joe, being an engineering company, we are not limited by the limitations of Manual J. We can accomplish a heat loss analysis using more modern and more accurate ASHRAE methods (or any other method we chose and PE stamp it such that it could be approved in every State.

Huh?

Remember your quote was:

Here’s the latest example of that even when this (load calc.) is not even needed:

That's what I'm suggesting you amend. I don't care if you are NASA, you've got a wanna be cyber-expert using your words to suggest that following code is a "questionable practice".
Too many hacks don't even do as much as the man. J, you want to criticize someone who emphasizes the importance? .....because you use better calculators?.....who the #e!! wants to pay for an engineer's stamp on a resi retrofit?

Joe, are you saying our $255 price for a more accurate PE stamped ASHRAE heat loss analysis is too expensive that no one would pay for it? I can assure you that isn’t true as demand always exceeds the size of our staff every year.

For the cited example, Manual J is indeed not needed and is not even appropriate given this is an existing building with an existing heat source that could be used to accomplish a far more accurate actual energy usage analysis. The only reason a Manual J or better predictive method would be needed here is if a totally different heating system was also being accomplished (e.g., going from a furnace to hydronic radiant floor heating, etc.) in which case a room-by-room analysis would be required.