MazdaManiac

iTrader: (3)

What more documentation do you need than the flow diagram?
Even if the blower would be perfectly balanced at 20k, its just a giant space heater at 12k.
Review your flow/density calculations.

morkusyambo

Sure, that way we can talk about this on the internet untill the end of time.

I allready told you the documentation I need.

MazdaManiac

iTrader: (3)

No you didn't, or I don't understand the request.

When a company makes a forced induction device, they publish what its performance is. You wouldn't know what device to use for what application and they wouldn't be able to make claims without it. I don't think a company has anything to gain by saying their product is less capable than its test parameters indicate.

If you are suggesting that there is some super-secret flow diagram in Stockholm that says that if you spin the blower over its design rating it suddenly goes back to 66% efficiency, than I don't even know what to suggest to you.
Physics is physics. The gas laws don't change just because you have *****.
Its like arguing who has the slower-firing gun. What's the point of that?

zoom44

then why are you asking on here? why not get him to answer your question about going over the rated speed and then post here his responses? he should be all the documentation you need.

morkusyambo

I'm don't care about what any company has to gain, or lose, since I don't own, work for, or hold stock in "any" of these companies.

I have clearly stated what I "believe" to be true, as well as the proof I requested. I don't need the proof. I allready stated my reason for that as well. You know this, since only a few of us have been posting here for the last few hours.

Twin-screws are twin-screws.

morkusyambo

Because I like this forum and joined it for technical "conversation", not "indoctrination".

The proverbial "he" is not all knowing and all powerfull. I like to run my thoughts off many people, as opposed to one or two. Thay way I have a better chance of having "unbiased opinions".

mac11

iTrader: (1)

The only bias I can see the mfgr of a s/c having in relation to their posted statistics about their products is to make their customers happy. That generally doesn't happen when they blow up their motors.

MazdaManiac

iTrader: (3)

But we are talking about blowing up their product. The flow map indicates that you don't have to get anywhere near the point of blowing it up before it stops being a useful device.
Really, even at its peak, the efficiency is nothing to write home about. Its better than a Roots, but that isn't saying much.

zoom44

thats not correct. First off all twin screw blowers come from one man- Alf Lysholm. He derived his work from Henreich Krigar who never actually built one. Sprintex used Lysholms designs that had fallen out of patent protection to make their twin screws. They never paid him for anything.

Art Whipple started making systems with the Sprintex charger in the 80s. SRM(the company Lysholm did all his work for) Split off the SC work to Opcon in 1990 and Later Opcon Autorotor split completely from SRM. SRM then created Lysholm Technologies to advance their Twin Screw work. Whipple started buying from them too.

Whipple licensed some of its kit production off to Kenne Bell so they could concentrate on GM while Kenne took over the Ford work

Lysholm Tech partnered with Eaton to bring their chargers up to a OEM standard. Then they merged with Opcon again in 2004 but the company has had so many problems they arent actualy building many blowers.

Sometime during this period Sprintex began building blowers again. Also since Lysholm/Oppcon cant seem to produce what is needed Whipple has actually started producing their own twin screws which incorporate all the newest tech/design for casting , rotor profile bearing etc.

So basically there are 3 companies producing twin screws - sprintex , lysholm and now whipple. none of which are using the same "castings". All derived from one mans designs and he never "sold" them to anybody- the company he worked for used them, sprintex used out of patent design for theirs and now whipple has created their own based on past lysholm designs with new tech design and materials.

mac11

iTrader: (1)

I completely agree with you, and RG and RD, etc. I'm saying it becomes a blow torch well before the RPM levels this guy is talking about spinning it too. Possibly causing the charge to become super heated and resulting in pre-ignition upon slight compression.

There are a whole lot of possible scenarios to consider when talking about running a blower of any type past the mfgr recommended redline. Not many of them have happy endings. I guess that depends on your idea of a "happy ending" though.

MazdaManiac

iTrader: (3)

Lol. Some people like their "happy ending" to culminate in an uncontrolled explosion.

mac11

iTrader: (1)

Just curious. Have you taken a look at the 6th gen roots blower maps - also listed as TVR on the eaton site?

The screws have been completely redesigned. They look pretty good.

MazdaManiac

iTrader: (3)

You mean the TVS? Yeah, I've looked at them.
They are up to 70% in the most efficient band, by the dynamic range is still too small for a rotary.

mac11

iTrader: (1)

do'h! yes! TVR is a car. deet de deeee

MazdaManiac

iTrader: (3)

I'll be fitting the Miata with an M45 in a few months.

mac11

iTrader: (1)

Just what I need, another miata running around that will run me down on the big striaghts.

morkusyambo

Castings was a poor choice of words on my part.

The rest is a very good indoctrination. You see, whether I got the history of the screw right or wrong, has nothing to do with how mine and MM's conversation started.

He has stated that you do not want to spin a screw above the manufacturer's recommended RPM because the power gains are negligible(my word, not his) and the the blower will become unstable and possibly blow up.

If you, or anyone else really wants to convice me i'm wrong on this one, then simply show me the tests and data that backs up your claims.

Otherwise, regardless of any of our backgrounds and experience, what has been stated in this thread about why we should do what Lysholm says are just "theories".

MazdaManiac

iTrader: (3)

The flow chart is NOT a theory.

mac11

iTrader: (1)

Manufacturers do not post recomendations based on theories!! HAHA!

and the R&D documentation you are asking us for is certainly not going to be made public by lysholm, opcon, whipple, etc etc.

If you want to see the results of the hard testing you have 2 options:

1) Get an job as an engineer at one of the above companies
2) Do it yourself. (buy a flack jacket and a scatter blanket while you are at it)

Please post pics.

morkusyambo

You're right, it just your interpretations of it that are.

morkusyambo

Have your last few posts contributed anything to this conversation??

mac11

iTrader: (1)

No where on the flow map does it show 20 or 25,000RPM. There is also a consistant and direct correlation between loss of adiabatic efficiency, rise of required driven power and rising RPM. On top of that there is a specification given by the OEM not to exceed a specific RPM. I don't see where theory comes into play in saying there is no tangible benefit - and that there will be a loss of life expectancy - in spinning it up to those types of speeds. Seems more like logic to me.

mac11

iTrader: (1)

What more do you want? Why would you expect Lysholm to release the findings of their internal testing? Maybe you should write to them yourself and talk to their engineers.

And outside of "some guy I know once did it" you have yet to produce a single piece of emperical evidance to say any of us is wrong. And even in your "some guy" story all your facts were wrong. So why would I think anything else was correct?


I don't really know what else to tell you. If you think the OEM's of this machinery are just yanking your chain with their numbers then go prove them wrong.

MazdaManiac

iTrader: (3)

What interpretations?
Are you even looking at the flow map? Do you see the lines of adiabatic efficiency? The drive HP lines? The RPM limits?
Even if you drew a straight line for the decline in efficiency (its not - its exponential), you would see that even if the blower were made out of unobtanium and balanced in zero-G so that it could never experience increased NVH or inertial breakdown, there would still be no point in turning it past its design limit.

There is nothing to interpret here. Its not a question of "Can you spin this blower to 15k and have it survive?". Its just the question "Why?".

If you are just looking to say it can be done, I'll save you the effort: Probably.
But you have accomplished nothing.
Air mass is all that matters. Ever. End of story (and its not me ending this story, its nature or God, whichever you prefer).
Oxygen mass = power. That is all there is.
The journey to that conclusion is what makes us all individually interested in the various systems and methods that get us there.
At the end of the day, all that matters is how many O2 molecules you can expose to gasoline and heat.

If you compute that your target HP is 350, you will need 41 pounds of air in the motor. Its that simple*.
Go look that up on the flow diagram and see what it gets you.

So, I would ask you - what is your interpretation of the flow map? What information does it impart on you? If you agree that the flow map itself is not theoretical, tell us what it describes? What do those lines at the end of the operational limit mean to you?







* Of course, its not that simple, but that is the essence of it from the point of view of the compressor.

rotarygod

Spinning a supercharger past it's rated speed is no different than spinning an engine past it's rated speed. In the case of a rotary you have 2 problems with this. The first is internal clearances between the sides of the rotors and the housings. This is an issue because the long distance between the front and rear bearings is unsupported. At high speeds the eccentric shaft flexes. Actually it always does but above a certain point it does so bad enough that the rotors actually hit the housings. The rotors on a supercharger would experience the same thing. They too run minimal clearance between rotors but at high speeds the flex will cause them to contact each other at some point. When this happens you'll be lucky if the only thing to break is the supercharger.

The other problem with revving a rotary real high is with the bearings. They don't live long as they spin faster and faster. As I said, bearing stresses go up with the square of the rpm. That means above a certain point, a few more rpm is a ton more stress and it only gets worse for every rising rpm. This is again the same thing that happens with the rotors in a supercharger. The question is will the bearings seize before the rotors contact each other or the casing around them?

This isn't even talking about efficiency as far as compression is concerned. There are ways to modify roots blowers that make them more efficient past the rated max blower speed. That is from the standpoint of compression. However in order to accomplish this, people take them apart, install tougher bearings and increase the clearances. This allows them to spin them faster to get more out of them. The downside is a loss down low from added clearance.

There's far more to it than jut spinning it faster because you think it can do it. Can it? Yes. How long? Maybe a minute. Maybe an hour. Maybe a day. Maybe more. There is one absolute fact that doesn't need any documentation and that is you are drastically going to shorten the lifespan of the blower. You can not change that fact. Keep in mind that at any blower, turbo, etc rated max speed and load rating, you are already losing efficiency compared to it's peak spot. Again this doesn't need written verification. That's how they are designed.

If you want to take a blower past it's rated speed limit and not risk hurting it, you have to modify it for this application. If you don't it's like taking a rotary to 16,000 rpm because you think it can.

There is no more documentation needed to show this is a bad idea. It's already been shown and the trend applies to every other blower out there. If you do it and get an engine failure from it, don't blame it on the supercharger manufacturer. I'd actually go a long way out of my way just to tell them about this thread if that ever happened. It's a bad idea and if your opinion says otherwise, you're wrong!