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Creeper gear for JD 420 S

crsutton81

crsutton81

Member
I want to fix a 2 seated carrier with provisions to put baskets on the 3 pt hitch about picking produce with where 2 individuals can ride along to harvest the stuff. I know Farmall made a hydraulic driven creeper gear that attached onto the pto and the clutch was tied down and hydraulic power drove the tractor via through the pto. There was also a mechanical version that was driven off of the fan belt then a chin to the pto. Was there anything made that was comparable to work on a JD 420 ? I have a fair amount of hydraulic motors, valves and such. Is it possible to tie into the current hydraulic system to run such as this ? If so how large of a hydraulic motor would
it take to make it work ? Looking to slow it down into around the .01 mph range without slipping the clutch to get slow enough to do a good job.
 
To get that slow it will need a fairly large hydraulic motor. Also a large motor makes more torque.

It's all in the math, motors are measured in displacement volume per revolution. You'll need to know the pump displacement at x RPM.

Then determine the speed the PTO needs to turn to get the desired ground speed. Match that to the speed the motor needs to turn, which can be adjusted with the chain sprocket ratio, engine speed, and a flow control valve if needed.

A lot to consider, but much better to work it out on paper than buying and installing the wrong components.
 
A lot of older compacts around these days at reasonable prices with super slow creeper gears.My MF 220 will barely move in 1st gear low range,I run the roto tiller in 2nd gear medium range to give an idea how slow it can run.Also have an Iseki about the same way.
 
.01 mph is really, really slow - about 50 feet per hour. In the 420's first gear you're going about 1.6 mph when the PTO is at 540 rpm. Doing the math gives a necessary PTO speed of only 3 to 4 rpm to back-drive the tractor at .01 mph. This is extremely slow and as a result would mean extremely high torque loads for a given power. For example, to transmit just 3 horsepower at 3 rpm will require a shaft torque of over 5000 ft-lb which would very likely break something. Even if you're talking .1 mph instead of .01 you're still talking about a torque in the PTO shaft of 500 ft-lb which is double what the engine would be able to subject it to.
 
All the parts you need are in a swing away auger used on a gravity flow wagon. Big farmers have quit using them for seed. Should find one at a sale. Should work for you.
 
If you run an orbit motor with a 420 for over a half hour (just guessing) the hydraulic system will get pretty hot. The oil volume in a 420 isnt all that much and there is no cooler. Adding a cooler to the return line from the orbit motor will help. It doesnt need to cool the entire return flow, just part of the return flow. A 12X12 inch cooler exposed to the air will be plenty good. I once rigged up an old air conditioning condenser in the return line to the reservoir to cool hydraulic oil on a hydraulic setup I made. It did the trick. This was a 20 gpm system. The cooler was branched off the return on a separate line so it cooled maybe a third of the return oil.
 
I know a guy that put 420 crawler ring and pinion in a 420 U for slow races. Won every time! Really slowed the little girl down.
 
My thinking is there wouldn't be any more torque damage potential than what would occur from running a rotary cutter ( bushog ) and it make it freewheel back through the pto. It used to was common on the 1 row Farmalls to do this about pulling tobacco harvesters to get slow enough to crop it. I have never seen anything locally tho on a JD M or 420. I will only be on hard flat ground and it'll only need to pull the tractor itself.
 
The best I can find out, the
hydraulic pumps on these tractors
are 3 gpm. I had some questions
about the hydraulic system getting
to hot to be able to do this. A
inline cooler would take care of
this problem. I guess the next
question is is 3 GPM of oil flow
enough to run a hyd motor and have
pressure enough to do so in this
application? Ideally if I could cut 1st gear down into quarters speed wise that would work good. If it was too slow, 2nd,3rd, and 4th gear is available on tranny to speed up.
 
The issue is just movement, not real work at all. The numbers would be correct if the hydraulic system and hoses were not pressure relief controlled. and could stand the force, and the rear wheels were not allowed to slip, and the front axle was chained down, and it was trying to pull a 20 ton block of granite. Jim
 
cockshut 30 with creeaper gear. Late models made after 1950 come to mind. They also have live pto and live hydraulics' and 3 point
CO-OP E3 is same tractor just differ cplor.
 
Factory pump is only about 3 gpm as you found. It also only develops about 1000-1100 psi. Trying to make too much more pressure will split the pump housing. Low volume and low pressure.
 
mvphoto85280.jpg
 
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