The 22-40 and 16-30 were the first models to use the heavy cast steel front wheels. Under a heavy drawbar load the front
end of the tractor liked to come off the ground. If the tractor was used for belt work this was not a problem. The conventional round spoke wheel was
standard equipment with the heavy 6 spoke cast steel wheel being optional. A number of rear wheel lug options were available and you can see them
here. Another new inovation was the use of a disc type clutch instead of the old style contracting band clutch. This new disc
clutch made for smoother operation and more holding ability. This new clutch system was used on all models until the end of production in 1930.
Also gone are the open bull gears in the rear wheels. The new large external type spur gears were attached to the rear wheel at the hub. These gears
were in an oil tight, dust proof pressed steel enclosure on each side of the tractor which provided an oil bath for the gearing.
A check plug was provided to keep the oil at a constant level with in the housing. 
In fact the check plug was usually used to let
oil out as the engine crankcase overflow oil from the Madison Kipp lubricator was plumbed into the bull gear housing. From the 16-30 the basic design and operation of all models
of Hart-Parr tractors would be the same. If you knew how to operate a 10-20 you could operate a 28-50 with out any problem. They were simple to operate and simple to work on. All engine and transmission parts were easily
accessible from the standing position. Click here to view the simple tractor design and the engine.