Terra Jet Rebuild Project Summary

March 2004

The objective of this project was to build a machine that could move snow in my driveway. I built a front end loader and installed it onto my garden tractor (see the tractor link). It works well, but the tractor is not built to handle the kind of stresses that the loader subjects it to. The frame twists and something needed to be done before the tractor was seriously damaged. That is where the Terra-Jet came in.

The unit was purchased in January of 2004. It is a model 400E. I believe it is a 1974 model. The original engine was a Kohler 399 cc twin. It came with a spare engine, 5 flat tires, and a bunch of spare parts including two front hubs, spare axles, all  in various states of disrepair, and a bunch of stuff in buckets that were so rusted, most of it ended up in the garbage. On disassembly, it was discovered that the tub was rusted through in a number of places. It obviously had seen some hard service. The tub was hammered and dented throughout the bottom. The chain drive sprockets were loose on the shafts and the rear axle was bent 0.100". There was 6" of ice in the bottom of the unit. Everything was corroded to a point where I started to wonder what it was I was getting into.

The first thing that had to be done was to repair the tub. It was cleaned, sandblasted and had new skid pans welded front and rear on the bottom. It was primed and painted with a good urethane rust inhibiting paint.

Once that was done, the frame was sandblasted and powder coated.

The original rear axle had a bend at one end of about 0.100". It was straightened, but I will only use it as a spare. I had a new one built using 4140 HTSR steel. The bearing seat length has been increased so that double bearings can be installed later on if needed. The weight on the back end of this machine has increased considerably with the changes that were made. Planning ahead sometimes pays off in the long run.

A structure was needed to hold the front end loader. A 3" schedule 40 pipe was slit in half lengthwise and that provided the base for the mount. (refer pic 2009). The tubing for the uprights are receiver tube for hitches. And you guessed it, the tube on the frontend loader that fits into the receiver is none other that standard 2" hitch material.

The transmission in the unit was a standard single speed forward and reverse unit. It was dismantled, cleaned, checked for wear (fortunately nothing critical) and reassembled with new bearings and seals. Just a note, it helps to warm the housings on assembly.

The hydraulic requirement of the front end loader created a bit of a problem. The twin cylinder Kohler and skidoo clutch arrangement would not work well in a hydraulic circuit. What was needed was a steady flow of oil for the loader. The skidoo clutch arrangement operates on a wide range of rpm's. The solution was to eliminate the original drive system, install a hydraulic power pack and run the entire system from that. So a swashable hydraulic piston pump was sourced. This would provide a variable flow of oil. It was installed onto a Honda GD411 diesel engine (9 hp but more bottom end than most 20 hp gas engines). A Charlyne hydraulic motor was used for propulsion. It is connected directly to the input  shaft of the original transmission. This was the simplest and most cost effective was to do it for now. The pump is swashable in only one direction, so a set of reversing valves was required to reverse the rotation on the motor, or leave the transmission in place and use that for direction control. Because the pump is only a single source, and the project had two circuits, ie: the front end loader, and the wheel motor, a system was needed to divide the flow. A pressure compensated adjustable flow control was used for this. It is connected directly to the output of the pump (pic 2154). The top output is the flow to the loader circuit. In operation the pump is swashed in the neutral position to give about 5 gpm flow. The flow control valve is set to 5 gpm. All the oil flow is sent through the loader circuit. The throttle peddle is connected to the swash arm on the pump. When the peddle is depressed, the pump swashes further to the full open position. This increases the flow from the pump. The control valve now diverts all oil flow in excess of the 5 gpm setting to the second output port, ie: the motor circuit and bingo, you start the wheels in motion. It is by no means a perfect circuit. You need to be carefull that you are not trying to lift a heavy load while you are in motion, as the pressure required to lift the bucket also ends up in the motor. It gets interesting. But with a little practice, it works  very well.

It is not very fast, but it has excellent pushing and lifting power. The unit weighs approximately 900 lbs. Most of the weight is in the back end. It will pick up enough heavy wet snow to lift the back wheels off the ground, with me sitting in the machine.. The bucket broke twice and needed reinforcing and repairs. Braces were also installed from the loader uprights to the frame of the machine to increase the rigidity of the bucket assembly. The reality is, this thing will push and lift more than its weight and thats good enough for me.

Now the body needs to be installed, the roll cage fabricated and installed and with summer coming, maybe a boat rack, for getting into those tough places that the truck just hates to go. When it's done, I will post the final product.

If you have any questions or comments, please, email me at rodkraft@shaw.ca. I appreciate your interest.

Project On!

albertv

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