Trailer gear mowers seem to be a hot item to pull with horses. My understanding is that they were originally designed to be pulled by a tractor at about 6 MPH and therefore had a lower gear ratio than a standard horse drawn mower intended to be pulled at about half that speed. So if you now pull a trailer gear mower with it's low/slow gear ratio, using a relatuively slow means of propulsion, ie. horses, seems the knife would be moving too slow for optimum cutting. Where is the flaw in my thinking?

Don't know about trailer gearing but the reason for them being popular maybe that they aren't as worn out as the road departments modernised sooner.

Frank,

I have no first hand knowledge of the trailer gear mower. I have knowledge of the Mc-D #7 regular and high gear mowers. Based on that experience and running the math, I doubt that the trailer gear is geared to less than a regular gear. The mower may be heavier to deal with the speed and abuse, but the cutting bar still needs to cut before the vegetation is pulled past the knife. On a #7 regular gear, the pitman flywheel makes 25 revolutions per one revolution of the 32" wheel. That is 50 strokes (1 out and 1 in stroke) per 100" of forward travel (32 times pi) The sections cut 2" each time the knife takes a stroke, so any slower than this would mean that the sections would need to be longer than 2" or the bar will start to bend the vegetaion over before it is cut.

The high gear makes 60 strokes per wheel revolution or 1.67" of forword travel per stroke. (100 divided py 60 = 1.67) The section is still 2", so the bite is just a little less than the forward motion.

Neal

Not arguing with you, Neal. Just asking. If the gear ratio were the same between a horse drawn mower and one desighned to be pulled by a tractor and the tractor travels twice as fast as the horses, wouldn't that cause the knife to go at a very high speed and vibrate the dickens out of the cutting mechsnism? Obviously mechanical problems are not my forte.

tractor mowers are usually operated at about 6mph. I've seen mowers going at about 20mph when a team gets into bee or wasp nests. Most of the time, they hang together unless they hit a rock.

Frank,

This is a discussion, not an aurguement. From a practical point a mower needs to cut the vegetation before the bar starts to bend it over. Anytime the knife is slower than the forward speed of the mower, you will get a ragged cut even if the knife and guards are perfect. A PTO driven mower still needs to move slower in the forward direction than the 2" per stroke. If a PTO mower is running at 6 MPH forward (fast in my opinion) then the knife needs to run at 3168 strokes per minute or 1584 rpm on the pitman wheel. At 3 MPH the knife only needs to run at 1584 strokes per minute (792 rpm flywheel) So with a PTO mower you match the tractor speed to the knife speed at the desired tractor RPM. With a ground driven mower, the match is built in. So whether the ground speed is 1 MPH or 20 MPH, as long as the mower wheels do not slip, the knife makes a cut before the vegetation is past the bar.

Now, since the speed of a tractor may be more than the horses, perhaps the trailer gear mowers have better bearings and lubrication. This would make them more desirable.

Since no one else has chimed in about the gearing of a trailer gear mower, it seems that the people that do know do not frequent this board.

I searched "trailer gear mower" and the only useful item (non auction) was this http://www.ruralheritage.com/messageboard/frontporch/13542.htm towards the bottom.

If you know someone with a trailer gear, have them jack up the left wheel and count the pitman flywheel revolutions per one turn of the wheel. Or send Norm Macknair an email. macknair.com

Neal

Neal, I think I understand...kind of...more or less...sort of. I'll take your word for it. Thanks. Frank.

Hmmm if it is ground driven and you do not change the tire isze I do not see any difference in the knife speed vs. the feed rate. If a horse travels at 2 mph the knife is going 1/3 as fast as the tractor at 6 mph and the horse is only going to cover 1/3 of the ground as a tractor. It is just like when I use a tractor to bale hay, the manual says to operate at PTO speed. Well the PTO speed is marked at 2100 rpm. But I get better hay pick up at 1500-1600 RPM (not going to mention the fuel savings). At some point the extra speed is not gaining you anything other then getting threw the field faster, and faster means more fuel cost and added wear on parts. Just my openion not fact to my knowledge.




Jim