powered, lightweight mower protoype

[Anonymous]

Haven’t tried it out yet, but it looks like it will offer very light draft for my Welsh-Mini cross team. Bar is 5′, with a 6.5 HP engine (probably overkill, but that’s all I had handy). The bar assembly was taken off an old McD New 4. The clutch assembly uses an idler pully like a rototiller. Tests indicate a bit of vibration that goes up the pole, so maybe I’ll add a tongue truck to reduce that effect if it drives the ponies crazy.

Any comments or suggestions are welcome.

[Andy Carson]

Very nice work, Daniel. I like how this is put together and i like the concept. How did you pick the pulley sizes? You’ll have to share them if they seem like the right speed, I think other might be interested in going something like this too. The only thing I can suggest is that I would consider adding a guard of some sort for the pulley/belt. I looks close to where you sit and i can see loose clothing etc, getting caught. Again, nice work!

[mitchmaine]

nice work daniel. how many rpms on the pitman?

[Iron Rose]

Looks great, keep us updated on how it works.

Dan Rasmussen
SE Minn

[Mark Cowdrey]

Nice looking job. I will be interested to hear how it works for you and your own critique.
How is the drive clutch engaged? Looks like a foot pedal.
Thanks,
Mark

[near horse]

That is a nice machine – well done Daniel. That brings up a couple of general questions in power cart fabrication. If one was making a PTO cart, how would you “measure” PTO output speed? Just calculate it from pulley sizes?

Also, how fast should the pitman run on a sickle mower? Do the engine driven models run faster than the GD horse models?

[Anonymous]

Thanks for the comments. Yes, a guard over the pulleys would be wise. I hate to think what would happen if a line got caught…ouch!

The pulleys are 10 inches and I think two inch, which gives way too much speed. However, I found that the clutch idler works like an accelerator, and speed increases as you push down on it. A light touch results in a reasonable knife speed, but if you floor it, it chatters and vibrates like crazy. I have since put the smallest pulley size I could buy on it, but now the belt doesn’t fit, so I can’t report if it’s an improvement.

I measure the pulleys: the ten inch has a circumference of 28 inches, while the small is 4 inches. That means a 7:1 ratio. If the engine at idle has 1200 RPMs, that means the crank wheel has 170 RPMs. Of course, that idle speed is just a guess, it may be way off.

To get the ponies used to the noise, I have been starting it up right next to them in their pen everytime I feed oats. At first, they bolted, but now they are fairly bored with it. I had them on an #9 last summer, and they were fine with it.

Believe it or not, the first time I fired it up near them, as soon as I pushed on the clutch and the knife started chattering, they looked relieved, kind of like “Oh, it’s just a mower!”

[Anonymous]

Some other notes if anyone is interested:

The hardest thing about building it was getting the balance right. At first I envisioned a virtual duplication of the original New 4 mower, but then realized that the extra engine weight would mean the seat had to be further ahead. That meant that the foot lift would have to be shortened, losing leverage. As it is now would be hard on the knees, I think, but I could add some scissors type of lever action, if I can figure out how to do it.

Getting the New 4 lead bar assembly figured out was hard until I found some giant nuts with thread that fit. Converting a #7 or #9 would be much easier, and might give a straighter pitman stroke.

Also, I wonder if the vibration would be reduced if the crank wheel didn’t have the lop-sided weight. I am thinking about making one out of steel plate that would be even all around, but that would mean a trip to the local machine shop. Any theories if that would be an improvement, or is that lop-sided weight necessary for cutter bar efficiency?

[Anonymous]

You push down on the foot pedal, which tightens the belt. It’s spring loaded, so if your foot comes off, the knife stops. Kind of a safety feature. But I have found that the belt tends to get stuck, and the clutch action stops working. Not good, because then the bar moves way too fast and threatens to fly apart. Need to figure that one out, too.

[near horse]

Thanks for the details, Daniel and keep us posted. “Small failures build the road to success” so hang in there.

[Mark Cowdrey]

Daniel,
Thanks for the reply. Glad to hear that a means to take it out of gear quickly and easily is a design consideration. I will be interested to hear the follow through on resolving that difficulty.
Again, nice job.
Mark

[Anonymous]

I figured out the correct RPM for the crankwheel based on the dimensions of a #7 I had in the shop for restoration.

5,280 feet/mile x 12 inches in a foot = 63360 inches divided by 104″ (the circumference of a 32-inch steel wheel) = 609 wheel rotations per mile.
If I count the crankwheel turning 26 times for every drive wheel rotation, it turns 15834 times in a mile. Divide that by 60 minutes in an hour, and you get 294 RPMs at a speed of 1 MPH.
So, if an average team goes 2.5 MPH while mowing, the crankwheel’s optimum speed should be 659 RPMs.
If my small engine runs at 2200 RPM, a reasonable speed to reduce noise and stench, and the pulley reduces output 7:1, then my cranckwheel turns at 315 RPM, which should be fine, because the ponies shorter legs mean their gait is half the speed of a “real” horse.
I’m a newspaper reporter by trade, so my math is probably wrong. Anybody see mistakes in my figures?

[Jay]

Daniel, my understanding of the flywheel lopsided weight is to reduce the vibration caused by the weight of the knife it’s self going back and forth- therefore necessary otherwise they wouldn’t have made it on the originals. What a nice looking machine. When are you going into production? Jay

[Anonymous]

Yes, I think you are right. Some of that vibration may be coming from slop in the pitman bushing. I need to build a few more of these things before I go into production. Do you think there might be demand for them if they cost around $800-$1,000? I can keep prices low if I use recycled cutter bars off old damaged mowers.
One option might be to build the cart assembly, then people could add an old cutter bar that they have restored and maybe supply a tongue, neck yoke and evener themselves. All I’d have to do is figure out a standard design for say #& and #9 cutter bars.

What I’d really like to do is figure out if this thing could run with an electric motor, because I hate ICE engines. Any engineers out there who could say what size of DC motor would work, and how much battery power (and weight) would give say 4 hours of mowing time?

[Billy Foster]

I like the electric motor idea. Our place is off the grid and in the summer our battery bank is often at 100% before noon. In the premise of reducing off farm inputs I have started thinking about how I can use electric motors to replace gas motors. The whole rig would probably gain a few pounds because of the battery weight. I wonder if one could build a set-up that bolted to a forecart?

Billy

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