I wanted to reduce back strain from using our weed trimmer. I added a factory shoulder strap from another machine to support the weight of the machine. My handlebar with twist throttle control allows good control of the trimmer. I made my handlebar attachment from scrap parts.
- 3/4 inch thinwall tubing
- 1 inch steel pipe
- #14 steel wire
- 1/8 inch and 3/16 inch steel rod
- 1/8 x 3/4 inch steel bar
- Two 1/4 inch hex head bolts, lockwashers, and nuts about 3/4 inch in length
- Cloth electrical tape
- Sheet metal screw
- Angle head grinder with metal cutting wheel
- MIG welder
Step 1: Boom Collar
See the first photo. I adapted a piece of 1 inch steel pipe about 3 inches long to make a mounting collar that fits around the trimmer boom. I slit the pipe lengthwise. The pipe will be compressed around the outer diameter of the boom. If the pipe needs to be compressed more than a little, make the slit a bit wider. I welded pieces of 1/8 x 3/4 inch steel bar at the sides of the slit. The pipe was stiff and did not compress much. I used a grinder to thin the pipe wall a little opposite the slit. Drill two holes in the steel bar and insert bolts. Welding thin metal to thicker metal is always a challenge. Set the welder for the thicker material and focus on it, but allow the arc to involve the thinner metal enough to cause it to fuse well, but not enough to blow holes in the thinner material. The second photo shows thinwall tubing removed from a junked fixture. I cut the curved portion and I cut it to length for my handlebar. The third photo shows my first attempt at a handlebar. Experience showed I needed to make some modifications.See the fourth photo. I moved the left side of the handlebars (from the operator's position) out about four inches. And, I changed the angle of the left hand handle. See the fifth photo. I covered the handle with cloth electrical tape for a better grip. You will also notice I welded a loop to the front of the left side arm for hanging a carburetor adjustment tool and a tool to hold the choke closed while the throttle is open during starting.
Step 2: Twist Throttle Control
I want to control the throttle with my right hand while the trimmer is in use. I decided on a twist control. My throttle control is very minimalist. I resized a short section of thinwall tubing so it fits neatly inside a piece of 3/4 inch thinwall tubing. See the second photo. The first photo shows the twist throttle control ready to be put in place. The steel ring fits over the 3/4 inch thinwall tubing. The twist throttle assembly fits tightly enough to avoid sloppiness, but loose enough to move smoothly. A drop of oil at the top helps the short piece that fits inside the 3/4 inch handle move very smoothly. The metal tab on the ring has a hole that provides an anchor point for the throttle wire. See the next step for how I resized the thinwall tubing to fit inside the right handle.
Step 3: Resizing Tubing
Slice the tubing lengthwise. (first photo) Use the vise to squeeze the gap closed and grind a "V" for the weld bead. (second photo) Weld. (third photo) Grind the weld smooth and insert into the 3/4 inch tubing. (fourth photo) Between the first and second photos I had to trim and fit the opening in the tubing until the tubing fit inside an original piece of tubing. It is a process of trial and error.
Step 4: Throttle Linkage
Fortunately, the line between the throttle lever on the carburetor and the tab on my twist control is close enough to line of sight that I did not need to rig any bell cranks, etc. to go around corners. I simply disconnected the factory throttle cable and bent a wire about #14 gauge. I had to experiment with bending the wire so it moved freely when finished, but also was not blocked by any fittings on the engine. The little spring on the carburetor is sufficient to return the twist control.
See the second photo. I carefully placed a sheet metal screw and some washers to keep the twist control from riding up on the right handle.
This project has helped me very much. It works very well and makes my weed trimming much less strain on my back.