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Would like some engineering thoughts on this!

T

Tractorcedric

Member
Location
Garland. Utah
I have mounted a John Deere three blade commercial mowing deck under the belly of a CA Allis. I found a tapered hub and some pulleys at the junkyard off of a M2 Gleaner grain head. The hub fits nice on the belt pulley shaft of the CA. The mower had a right angle one to one gearbox on it. I first thought about making a driveshaft with a pulley on the end that could belt up to a pulley on the 540 pto. Then I saw that the belt pulley turns 1280 rpm. I don't know what this mower was on, but I bet it was driven at crankshaft speed. In the picture from the back I have the gear box setting on blocks so that it would line up with the drive and driven pulleys. This set up would use two shorter belts. If I just used some idler pulleys instead of the gearbox I would need one very long belt. Saw on Ebay a hexagonal belt 150" long for $60. Would that kind of belt work good for this? Would the gearbox rob too much power? Should I go back to the drive shaft setup? Can't sleep!!!
cvphoto74553.jpg


cvphoto74554.jpg
 
Is there a serial number plate on the mower deck? It will contain the model number of the deck. If we knew its original application, maybe we can determine the rpm of the drive shaft.
Drive shaft option is better than belts!
 
I replied to a previous thread of yours about this mower with an offer to get you the details on the speed at which a similar DEERE mower is driven.

I don't know if you didn't see the reply or didn't want my help???

If you would like me to get the gearbox and belt drive ratio giving the spindle speed I am willing to measure and count that for you.
 
Using the right angle gear box is just fine. Most mowers use belt pully speed drive, or a overdrive to about that speed from a PTO. With 3 blades, the tip speed will not be excessive. Bush hogs with one longer blade assembly do drive closer the PTO, but that is not this. There is no reason not to use flat idlers for belt tensioning (such as the one on the mower deck. Jim
 
That should be a good setup when you are done. I have thought about making a off-set ditch bank mower. The deck could mow at an angle but the tractor would be somewhat level.
Anyway, back to your problem, do you know what the blade spindle RPM is? I think that would be the main thing to know so you could get the correct size of pulleys. The JD garden tractors ran the gearbox off of a transmission shaft, and I have no idea what the RPM of that shaft is.
Anyway good luck on your project.
 
Woods uses one very long belt to do that job. You could have quite a challenge getting the correct one. When the PTO is used to run a mower, the pulley is very large, like 18" or so. I believe I have one here.
 
Yes I could use your help! Thank you! So the one pulley I got to go on the belt pulley drive hub is 10.5 OD. I had to grind just a tiny bit off of the axle housing to get it to clear. So it would turn 1280 RPM at near high idle. All of the pulleys on the mower deck are 6" OD. And the one I have to drive the center one is 6" as well. I have heard that a tip speed of the blade should be no more than 3400 FPS. Is that correct? Since it is a 60" deck, each blade is 21" because of offset. The center one is in front. So the tip would be 10.5 from center of shaft. If I use the gearbox or just a belt that (could) stay the same, right? My first thought was to mount a counter shaft under the tractor and run it off of the PTO. But I can't put a very big pulley on the PTO. Just looking for options!
 
(quoted from post at 14:49:40 02/06/21) Yeah, I have looked real close for a serial number or model number but no luck. Like I said in another reply, Is a tip speed of 3400 FPS correct?
Click to expand...

Your mower appears that it may be for a "front-mount" mower unit.

If you go to https://partscatalog.deere.com/jdrc/ and type in "60" and look at some of the resulting front-mount (or other) mower decks you can probably figure out what you have.

Finishing mowers typically operate with a blade tip speed of around 17,000-19,000 feet per MINUTE.

To achieve the lower end of that range your spindle speed needs to be around 3100 RPM's IF my math is correct, DISCLAIMER: better double-check it and triple check it and rely on your own math!

The math:

21" bade diameter X 3.141592 pi X 3100 RPM's / 12 inches in a foot = 17043 feet per minute.

So if your tractor's belt pulley shaft that you are sourcing power from turns 1280 RPM's you need a speed INCREASE of at least 1 : 2.42 between the tractor and mower.

Also, for everyone's safety, GOOGLE "finishing mower blade tip speed" to verify that the 17,000 to 19,000 feet per MINUTE is correct.
 
(quoted from post at 18:36:48 02/06/21)
(quoted from post at 14:49:40 02/06/21) Yeah, I have looked real close for a serial number or model number but no luck. Like I said in another reply, Is a tip speed of 3400 FPS correct?
Click to expand...

Your mower appears that it may be for a "front-mount" mower unit.

If you go to https://partscatalog.deere.com/jdrc/ and type in "60" and look at some of the resulting front-mount (or other) mower decks you can probably figure out what you have.

Finishing mowers typically operate with a blade tip speed of around 17,000-19,000 feet per MINUTE.

To achieve the lower end of that range your spindle speed needs to be around 3100 RPM's IF my math is correct, DISCLAIMER: better double-check it and triple check it and rely on your own math!

The math:

21" bade diameter X 3.141592 pi X 3100 RPM's / 12 inches in a foot = 17043 feet per minute.

So if your tractor's belt pulley shaft that you are sourcing power from turns 1280 RPM's you need a speed INCREASE of at least 1 : 2.42 between the tractor and mower.

Also, for everyone's safety, GOOGLE "finishing mower blade tip speed" to verify that the 17,000 to 19,000 feet per MINUTE is correct.
Click to expand...
inishing mowers that I am aware of have been in 16,500 to 17,000 feet per MINUTE. Math looks good.
 
Push mowers crankshaft rpm is 3600. ON 21 inch mower blade center to tip is 10.4 inches. Use 4th grade to get tip speed!!! Using pie D on 24 inch blade gives 6.28 feet per revaluation or376.8 feet per sec, or 13,608 feet per min. Should one wish to find miles per hour divide 816,480 by 5280.
 
The belly mount JD decks come in to major styles. Those driven from the transaxle, shaft forward to the gear box use a 2000rpm pto. on those, the gearbox is rear facing. The front facing versions are driven by an electric pto mounted on the engine.
Those, of course are driven at engine speed modified by the pulley size. Most I've dealt with drive the deck at .75 times the engine rpm.
 

For my 2 cents. The longer the belt, the harder it is to size up a replacement once they stretch some unless you write it down. They stretch more anyway. Once the bearings on those flat idlers start to go, then they start throwing belts and especially the longer belts. A bearing going bad or bent mount or being just a little off line will end up with thrown belts which is something I fight with the rototiller where nothing stays tite because of the vibration. That is the usual problem with the riding mowers that use a lever to tighten the idler pulley held by a spring to start the blades. Of course a thrown belt requires a shut down and sticking your fingers where it is hot.

If you can keep the belt tight all the time and start it with the pto then you are in good shape. The longer the belt and pulley set up, the easier it for cut grass and weeds to jam it up.

Not sure I helped you here but something to think about.
 
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