Fixing the Mulching Mower

[keerym]

Alright, this is Mike again from the Milwaukee School of Engineering. I have moved to the next stage of my project for school, and its time for some more input from professionals. I have decided to work on improving the mulching mower. What I need to know are the problems that you have with mulching mowers, and under what conditions you encounter these problems. Again, I have several ideas of what goes wrong, but I want to hear from you, the professional. This is the problem stating stage of my project, and it can prove to be the most difficult, but also the most important. I welcome any and all input you have to share. Thanks,

Mike

[LWNMWRMN]

I think most of the problems are not in the mowers but in the conditions they are being used in. I don't think there is a fix to wet or tall grass. A mulching mower is not going to cut off 4" of wet grass and leave it looking like a carpet.

[keerym]

My idea thoughts took a left turn this afternoon when I was riding to the Toro dealer to gather information. There are no formulas for building a mulching deck, nor any real evidence of what works and what doesn't work. For me I need something else I can solve with a new and innovative idea. My thinking was that you all need to change blades frequently, right? Would a device that acts as a quick change for blades be a good idea? I am pretty sure I could come up with a quick coupler, I would just have to over come some safty concerns and some concerns about debris build up. I know I could come up with something, but my question is would this be something you use?

Mike

[mowerman90]

Keerym,

I'm in Central Florida where we mow pretty much year round. Almost everyone here uses dedicated mulching mowers now. I've been using one since 1994. The biggest problem I or anyone else has is in the summer, (say July), when it rains almost every afternoon and you can almost see the grass grow. Tall, extremely thick grass will sometimes (if you're mowing too fast) leave a streak of partially uncut grass that requires us to double cut. This happens unless you slow to almost a crawl. I've often thought that if my deck had an auxillary blade (say 10") to the rear and centered on the deck it would eliminate this streak.

As for your idea of "quick change blades" I don't think it would be much of an improvement over a socket and ratchet like I use, and I'm sure it would present some sort of safety issue.

[mowingmachine]

Your trying to do something the lawn and garden industry has been working on perfecting for years. The biggest complaints I have found with multching decks is they take too much horsepower, you have to mow more often because deep grass is a problem and they leave strips of discharge on the right side and between the blades. A lot of blade manufacturers have been trying to make a blade do the job but I think the answer is in the deck design. If you are talking to Toro you are probably, in my opinion, talking to the best multch deck designers so far. Hope this helps.
Mowingmachine

[Daryl]

Mike.

We have been using mulch mowers for the last several years. Personally I think the biggest problem with some of them is that the mowing chambers need more air flowing through them to mix with the grass. Would help when it's wetter and when it's thicker. The more air is exchanged the better it seems to cut.

Daryl

[Jet boater]

I agree on the deck depth.

I also wonder if counter-rotating blades would help any on the "streaking"?

[keerym]

The counter-rotating blades are a good idea, and I have thought of that, however the idea has been taken. Bushhog has mulching mower decks out with counter-rotating blades. I like the idea of adding some air flow, and possibly creating a swirling effect inside the blade chamber. This is how modern engines work, the piston and head is designed in a way that swirls the intake air to mix the fuel with the air and disperse it better. If one could design a deck, or add a swirling type of air to the deck, maybe the clippings would tumble around and disperse better. Just a thought.

Mike

[Jet boater]

There was an article in Machine Design within the last 6 months on using Fluid Dynamics to mathematically model and design a mower deck.

I don't keep back issues but you may be able to find it on their website.

May be helpful in your quest.

[Jet boater]

Found it.

Go to:

http://www.machinedesign.com

and search for "Go With The Flow"

It's the August 3, 2000 issue.

[Roger]

I've thought about this issue and wonder if some design studies have been done on a different design, one that separates the mowing function from the mulching one.

The present designs all are some small variation on the same idea - changes with the basic mowing process. The deck with blade was intended for cutting blades off at mowing height. Then variations are made to decks (e.g. kicker plates) and blades (e.g.double cutting edges, Gators) to mulch the clippings. Often the changes do the the mulching diminish the basic function of cutting the blades of grass (e.g. less blade lift).

Perhaps a design could separate the two functions. Keep the mowing deck, with good high-lift blades, to do the best possible job of cutting blades of grass. A separate function (e.g. chamber, bin, or ???) with some device to mulch the clippings and blow them back on the lawn.

I'm not about to propose a design for the second function, drive components, method of mulching, or other details. But, the point of the design would be to separate the functions so that each would be done without compromising the real needs of the other. The design of such a machine is best left to the machine designers who know how to deal with parts, power trains, etc.

As pointed out earlier, successful mulching with wet grass is much needed, but apparently very difficult to achieve. The design of my idea would have to incorporate this need as part of the criteria.

[keerym]

The idea of the separate mulching chamber is where I am at right now. I do not have the resources or the time to test different deck designs, so I am going to try to come up with a design that mulches clippings and debris in a separate chamber, then return them, evenly, behind the mower in a safe manner. The design of the chamber and the drive system for the chamber is part of the project, this is an engineering school, and the better you can make it look, the better your grade for the project. I will be running with this design, once I check patents and other things, I can't use something that someone else has rights to. I checked out that article in Machine design, and that software would be great for this project, but unfortunatly I don't have access to that at the moment. It will be an interesting piece to include in my report however. I would like to thank everyone for being so helpful, and if you have any more thoughts on this or ideas, I would love to hear them.

Mike

[jason2]

How about using something to disperse the clippings like what a combine uses? After a combine seperates the seed from the rest of the plant. The material is carried back to a straw chopper. Designs differ from combine to combine. On some models the straw after being chopped up drops on to a spinning disc which flings the straw outward, similar to a broadcast spreader. Other models use air to blow the straw.

I can see one distinct disadvantage to this system. when mowing next to beds, etc.. it would be a pain to have the grass blowing all over. Plus their could be liability issues if something like a rock passed through the system and was flung out the back and hit something.

But just thought I'd give you some feedback. Sounds like a neat concept to seperate the mowing function from the mulching.

[lawrence stone]

The ultimate mulching mower was produced by Toro over 10 years ago.

Here is my version of the ultimate no discharge 48" trimming mower.

The 16hp magnum or better is required for any serious production. A 22hp Command is what is needed for this mowing deck. As you can see the deck is a high dollar welded
unit and a real tough customer when it comes to hitting large objects while trimming.

http://albums.photopoint.com/j/View?u=1209854&a=9499679&p=31207245&Sequence=0&res=high

http://albums.photopoint.com/j/View?u=1209854&a=9499679&p=31207248&Sequence=0&res=high