- Joined
- Oct 30, 2019
- Messages
- 225
We borrow this little 3-wheel dump truck from a neighbor, and it's lived/sat here for the last few weeks so I have started fixing things on it
It is a 3-speed stick shift with a hydraulic dump bed and an additional PTO. So far the things I have noticed it needs TLC for:
I decided to tackle the gas pedal/idle behavior first, suspecting wear in the pivots and linkages between the pedal and throttle/governor assembly.
First I took apart the gas pedal hinge assembly itself, found that there wasn't a ton to do there but clean and lubricate. The pedal hinges on two bolts with nylock nuts, so that was adjustable to clean things up; and the bushings themselves were in fine enough shape. There's a tie rod end that I greased and adjusted to take some extra motion out of the rigid linkage that goes from the pedal back to the engine bay.
I didn't take pictures before disassembly, so I'll use this "after" picture
The black rod running horizontally across the top of the bay below is the main subject. The bronze-colored steel rod coming up vertically on the right side is coupled eventually to the gas pedal, combines that input with the hand throttle, then the black rod translates that motion across the engine bay to the governor/carburator side of things.
I had found that by pushing sideways on that black linkage, the main bushing it sat in was sloppy enough that it would rotate and push/pull on the downstream linkage (through some ball joints/tie rods), and that slop would allow the carb to basically move from idle to full throttle and back - without the gas pedal or hand throttle side of things moving.
This seemed to be where most of the unreliable idle behavior was coming from. Depending on what was vibrating/rubbing in the right way, and which way the wear in some of the joints lined up, the idle would end up being higher or lower.
Black rod removed, this plastic bushing was the subject that allowed for all the lost motion.
Measuring, it's nominally 5/16". The bushing ID measured at ~0.330, and the area where the rod's paint is worn off measured 0.309 to 0.310 (slightly undersized from the rest of the 5/16" rod that was around .312 to 315 with paint/etc).
I'm sure this was all just manufactured as nominally 5/16", but since this appears to be the worst cause of the slop let's try and make the new bushing as snug a sliding fit on the rod as possible).
Let's replace that plastic bushing. If I had a 3d printer then this wouldn't be a bad candidate for a new plastic one, but I have some oilite bronze so let's use that.
Nominally 3/4" major diameter, 0.5" minor diameter (the hole in the sheet metal bracket is around 0.495, so the 0.5" plastic was a nice snug fit), and we'll try to hit exactly or just-undersized 5/16" ID and let the rod wear into it.
For the ID I used an N drill (0.298), and took a shot at boring the ID out, to get something like 0.310. It turns out my adjustable hand reamers start at 0.500+, so I couldn't ream this to 0.310. I don't have a boring bar that tiny, but in my drawer of broken HSS stuff I found a cheap homeowner-grade masonry drill bit with a carbide insert.
What about using diamond files to fix that tip geometry and turn it into a tiny boring bar?
I did that but didn't take any pictures. It went ok, I didn't have my center height set and it ended up rubbing its way through, but I got there. Will revisit this next time I need to bore a small diameter.
Parted off, chamfered. I made the minor OD 0.495 so it was a nice press fit into the sheet metal bracket, and the rod was a snug fit (especially since I needed to force the non-worn section through first) inside but wore in just with some manipulation by hand. I didn't do anything to retain the bushing in the bracket, but maybe I'll go back and hit it with a center punch to raise some material just below the bracket, rather than make an explicit retaining feature.
The old plastic bushing had a friction-fit ring pressed onto the bottom that acted to retain it.
Reassembled, looks good/right
And back to the future. With the engine running, I pushed sideways on this linkage in a way that canted the linkage previously - causing the engine to surge or stall depending which way I push it. Now there is absolutely zero change in throttle plate position.
I went back and adjusted the tie rod on the gas pedal, since the range of desired motion for the gas pedal is now different from the range before (since it had to permit so much slop)
thanks for reading... if I get into the transmission linkages or anything else on here and make parts, I'll probably post them back in this same thread.
It is a 3-speed stick shift with a hydraulic dump bed and an additional PTO. So far the things I have noticed it needs TLC for:
- The shift linkages all have play/slop, so until you're used to the behavior it can be a challenge to find the cleanest path that aligns the slop to shift in a timely manner
- It idles great, but generally you need to keep the idle high because sometimes the idle will drop and stall. so you end up keeping the hand throttle up higher to set a high floor for the floor pedal.
- The high/low range shifter for the driveline appears to be stuck (not sure if it's a 2-speed rear axle or a tail on the transmission, haven't looked at this yet)
- Overall probably due for oil changes, belts, and filters but if I don't get to that, the owner eventually will.
I decided to tackle the gas pedal/idle behavior first, suspecting wear in the pivots and linkages between the pedal and throttle/governor assembly.
First I took apart the gas pedal hinge assembly itself, found that there wasn't a ton to do there but clean and lubricate. The pedal hinges on two bolts with nylock nuts, so that was adjustable to clean things up; and the bushings themselves were in fine enough shape. There's a tie rod end that I greased and adjusted to take some extra motion out of the rigid linkage that goes from the pedal back to the engine bay.
I didn't take pictures before disassembly, so I'll use this "after" picture
The black rod running horizontally across the top of the bay below is the main subject. The bronze-colored steel rod coming up vertically on the right side is coupled eventually to the gas pedal, combines that input with the hand throttle, then the black rod translates that motion across the engine bay to the governor/carburator side of things.
I had found that by pushing sideways on that black linkage, the main bushing it sat in was sloppy enough that it would rotate and push/pull on the downstream linkage (through some ball joints/tie rods), and that slop would allow the carb to basically move from idle to full throttle and back - without the gas pedal or hand throttle side of things moving.
This seemed to be where most of the unreliable idle behavior was coming from. Depending on what was vibrating/rubbing in the right way, and which way the wear in some of the joints lined up, the idle would end up being higher or lower.
Black rod removed, this plastic bushing was the subject that allowed for all the lost motion.
Measuring, it's nominally 5/16". The bushing ID measured at ~0.330, and the area where the rod's paint is worn off measured 0.309 to 0.310 (slightly undersized from the rest of the 5/16" rod that was around .312 to 315 with paint/etc).
I'm sure this was all just manufactured as nominally 5/16", but since this appears to be the worst cause of the slop let's try and make the new bushing as snug a sliding fit on the rod as possible).
Let's replace that plastic bushing. If I had a 3d printer then this wouldn't be a bad candidate for a new plastic one, but I have some oilite bronze so let's use that.
Nominally 3/4" major diameter, 0.5" minor diameter (the hole in the sheet metal bracket is around 0.495, so the 0.5" plastic was a nice snug fit), and we'll try to hit exactly or just-undersized 5/16" ID and let the rod wear into it.
For the ID I used an N drill (0.298), and took a shot at boring the ID out, to get something like 0.310. It turns out my adjustable hand reamers start at 0.500+, so I couldn't ream this to 0.310. I don't have a boring bar that tiny, but in my drawer of broken HSS stuff I found a cheap homeowner-grade masonry drill bit with a carbide insert.
What about using diamond files to fix that tip geometry and turn it into a tiny boring bar?
I did that but didn't take any pictures. It went ok, I didn't have my center height set and it ended up rubbing its way through, but I got there. Will revisit this next time I need to bore a small diameter.
Parted off, chamfered. I made the minor OD 0.495 so it was a nice press fit into the sheet metal bracket, and the rod was a snug fit (especially since I needed to force the non-worn section through first) inside but wore in just with some manipulation by hand. I didn't do anything to retain the bushing in the bracket, but maybe I'll go back and hit it with a center punch to raise some material just below the bracket, rather than make an explicit retaining feature.
The old plastic bushing had a friction-fit ring pressed onto the bottom that acted to retain it.
Reassembled, looks good/right
And back to the future. With the engine running, I pushed sideways on this linkage in a way that canted the linkage previously - causing the engine to surge or stall depending which way I push it. Now there is absolutely zero change in throttle plate position.
I went back and adjusted the tie rod on the gas pedal, since the range of desired motion for the gas pedal is now different from the range before (since it had to permit so much slop)
thanks for reading... if I get into the transmission linkages or anything else on here and make parts, I'll probably post them back in this same thread.