Finish mower blade

[BigDave]

Could it be possible that Villengineer and Nomad are both partly right and partly wrong?

There are plenty of businesses in Turkey & the U.S., as well as universities in both countries. Maybe their roles and relationships are different in each country. Maybe relationships, even between private companies & universities vary within your own countries. Although I work for a neutral party(non-profit), some companies require me to sign non-disclosure agreements before I can see any of their data, while their competitors in the same industry will actually go as far share labor costs and their bids with me, even though they are of no interest to me. Suprisingly, even within the same company, such desparities exist.

A few more examples:

I've actually was at a symposium in which a professor and his students presented a flow visualization study of a riding lawnmower deck which was sponsored by a private company. They put plexiglass under the deck at grass level, & injected paint into different locations to study the resultant flow pattern on the ground. It was awhile ago, but I know they tried several different blade designs. No CFD was involved. This presentation, given the less than glamorous subject, was scoffed at by some of the academics in the audience.

I also worked for a private company who's computer acquistion budget was $10-12 million dollars per year, but I also worked for a University which built a super-computer with 4096 processers. Which cost more? Which is more powerful? Okay, the 4 Hewlett-Packards with 32 cpu's each set the company back 2 million dollars, but I'm not sure if anyone really knows what the University's machine cost, since it was built by staff & students. Both machines cranked out CFD runs like there was no tomorrow. Private companies are about making a profit, so sometimes things that have no reason to be classifed as proprietary are hidden away from their competition. Some companies don't want their competition to realize that they even know the basic equations. Other companies are very open, and professor's who design a piece of equipment actually get to bring the equipment to symposia to present to academia prior to public release by the company. I've seen it happen first hand twice.

 

[Villengineer]

BigDave, you are right. I was wrong to make generalities. There are always exceptions and I forgot some wise advice I was once given: Any statement including or implying always, all, etc.. is likely false.
You've peaked my curiousity with mower deck example. I'm assuming that they were able to control the experiment and get specific flow patterns and not just fling paint everywhere. It sounds like it would have been very cool to watch. Now that's a lecture that would keep my attention.

 

[HayDR]

BigDave,
You are correct it's a bottom line thing. What about planned obsolescence? Should a consumer know the expected life of a product? Who should decide what information should be public and or private?

 

[nomad]

It's 10 AM here and good morning to me and nights/evenings to you. Well, there are a lot to response

</font><font color="blue" class="small">( Just looking at the final blade shape we recommended does not give the full picture of the research. )</font>

Ray, the final blade picture tells me the full picture of flow patterns your final blade produces because it's shape gives ONLY a certain flow pattern which can be found by a detailed experimental analyse, you know. If I had a lab with some simple facilities, I'd understand whether you took the local small scale turbulent flows in the deck which will be important for recyling and recutting one grass blade several times in the deck or not. This is what we actually are discussing and I am saying (to Villengineer) I am sure there is no such a blade designed "intentionaly" to take "recutting mechanism" into account. Villengineer says how I can be so sure and I'm trying to tell him that recutting grass in his mower is just a "lucky" (undesigned) output.

</font><font color="blue" class="small">( All that said, the customer probably only cares about the performance. Not how it was achieved. )</font>

Yes, the users only cares about the performance - but what if they are told "our mower is designed ALSO to do *this" work too."? which was actually not designed? Villengineer-like someones are claiming that "yes, recutting mechanism too is included in the design" - Villengineer, if it's really being designed as you and they are claiming, I could ask you and them a question or two that may put you and them into trouble. If they are really designing that mechanism of recutting, this means they have a control over the flow in local small scales. If they have that control, then I am asking them to design a special mower with my constraints. For ex., I want 77% of the cut grass to be recut twice and 20% of them to be re-cut three times. If they really have the control of re-cutting mechanism (must be so because you are saying that mechanism is being included in the design), then they must be able to make such a mower I requested. I'll pay all expensive costs of making such a mower if they can make one.

As for private companies; they hide their researches mostly against their competitiors who aren't more knowledgable than a good knowledgable scholar in basical equations. Remember that even some basic equations well known by scholars at faculties&institutes are being considered by some private companies as their trade secrets. This can be understood because most of small and medium size MFGs don't know even the basic equations which are used as input to the computational algorithms. For ex., take Gilmore - who are experienced and specialized also in CFD. What did Ray say here? He said they used Fluent software package which I too had used much at its early days. Now, even if Ray doesn't tell me what basic equations he used in their blade design, I know what they used - because I know what equations are used by the Fluent when solving a problem because they publish them equations in their manual/handbooks. So to speak, somethings for trade reasons may be kept as their trade secrets, but these are against their less-knowledgable competititors - not against people like me who can understand what they are really doing without seeing their research labs. Hey, they aren't using any "super-light" techniques, are they? Ps: I used this super-light term to define faster speeds than the light speed which is in out of classical science field.

Dave mentioned someones (a private company financed study) presented a flow visulation study in the deck. So, someones are open to public - although such studies like flow visualization shows only what is seen in the final blade design. Such techniques like flow visualization aren't a "real" part of design process - they are only a kind of feed-back control technqiues which are used to see what flow patterns you obtained from your blade design using other techniques (directly analitic or computational using analitic equations again.) Finally, owning faster computers by private companies doesn't tell much about how their science is ahead of universities/institutes. Faster computers are only for finer and finer meshes which will linearize (discretize/digitize) nonlinear terms already existing in "analitic" equations they use as input and equations well known by anyone who studied PhD in engineering or by MSc in mathematics/physics. So, since all those private companies are using same analitic equations any person who knows about analitic equations can comment on their research studies of private companies even if he didn't see their research process. Okay, private engineering companies like Deere or Gilmore maybe also adding some extra terms (emphirical terms) to analitic equations and usually these emphirical terms are kept as secret - but these terms are "actually" ONLY a simplification of analitic equations and such terms aren't much important for people understanding the mathematics. Because whether you add such an emphirical term or not, you aren't changing the form or degree of nonlinearity already existing in analitic equations. Yes, such emphirical terms/parameters/functions can be only secrets of private companies, but they are only against their trade competitiors. Anyone knowledgable about analitic forms can see "what can be done and what can not be done" when you use an analitic form directly or indirectly by adding some emphirical things - Re-cutting mechanism to re-cut a grass blade several times in the deck is, to me, in such things that are almost impossible to design without a full flow control, a control which is needed in re-cutting process.

Anyway - but, re-cut is already being done by your mower? Well, I told it why it does and will tell again; That "re-cut" is an "undesigned" result or a "rough" expectation only from a "designed" recycling process, usually done in the deck design, not in the blade design. Mechanisms in the designs of blades are "cutting" and "lifting/propelling" mechanisms and even calculations/computations of these mechanisms are based on "averaged" quantities of the grass blades and flow parameters. Hope things clear now?

 

[smilingreen]

Nomad,
I am just wondering.....what is your point?? You keep trying to tell us that some sales guy is lying to us. Have you sometime in the past been ripped off by some salesman that sold you fake titanium blades? I really have lost the meaning of this conversation.

 

[nomad]

My point in this conservation? It's already understood by everybody (Villengineer, Egon, me, Ray from Gilmore, BigDave, and many other topic contributors in this engineering classroom.) So, what do you mean by "us"?

Anyway, returning the topic - Attached picture is a simple shematic drawing of a finish mower blade. Just posting it for Ray as he may be foreigner to finish mower blades. I believe this blade is one of latest designs on which much more research studies than any other blade were done. I maybe wrong - and waiting to hear "nomad, you are wrong, there are more complicated blades"- or "nomad, you're correct? "

 

[Egon]

Looks just like the one on the lawn mower I bought back in 1979.

Lets see; thats about 25 years ago.

Egon

 

[BIGUN]

</font><font color="blue" class="small">( Ths past Fall I welded small "wings" to the upward-canted part of some RFM blades in an attempt to get more lift. It worked remarkably well and moved much more air. The extra lift resulted in the grass looking better (no long fuzzies where the tires pushed the damp grass down). It also made leaf cleanup a snap.

I bought a set of Gatorblades a couple years ago and was very underwhelmed with them. My simple experiment tells me the manufacturers could make more effective blades. This could be your chance at early retirement......................chim )</font>

More effective or desirable would of course depend on the user’s point of view. My old Ariens came with high lift blades that did a great job of sucking all the lose sand and dust up off my rural yard which lacked sufficient ground cover in many places especially in the shade of the large oak trees. After suffering being covered with dirt after each mowing session for a couple of years and wearing (sand blasting) holes in the curves of a couple of sets of blades I was in the market for some low lift blades. I found and purchased some that had significantly less lift and were much more desirable for my needs. /forums/images/graemlins/smile.gif

 

[nomad]

Really looks like the one seen 25 years ago?
Then, Toro, KK, FC, Landpride and so on have not done anything on the mower blades in last 25 years. See, for ex., this blade attached - this must be Toro's recycler mower blade as far as I remember.

If your Cadillac mower has more bents, saddles and holes than this, then look at the next post where I'm posting several mower blades. Which is yours?

 

[nomad]

attachment: mower blades