Repair of damaged Mbox M1a Caterpillar Scraper (completed)
Posted: Sat Feb 13, 2021 11:31 pm
This Major Pack M1a Caterpillar scraper was gifted to me some time back. It one of my favorite Majors, so I wanted to do it justice. I've pointed out all the problems in the photos but I'll list them here so I can go through my choices for restoration.
Scraper body:
1. The pin which allows the scraper body to hook onto the tractor was broken off flush. I cut a short piece of steel rod and placed it into my drill (to make a mini lathe). While turning the rod, I used a small file to make the round over on one end. Next, I used a pin vice to drill out a small hole (the same size as the now shaped rod) where the connecting pin used to be. Test fit the pin, cut to right length and secure in hole with epoxy.
2. I fashioned a new upper half of the bed raise/lower lever using a scrap of plastic laminate. I shape the plastic, while leaving the part I'm making, connected to the bulk of plastic at what will be the base of the leaver. This allows me to work with a small shaped part while holding on to a much larger amount of material. When I'm happy with the shape of the part, I cut it free at the base. A trial fit or two determines how tall it needs to be (shortened by removing excess from the base while holding the part with needle nose pliers). The remains of the old lever are filled off leaving a nice flat spot for the new part. Secure the new part in place with epoxy.
3. The push point was fashioned out of a small piece of aluminum. I shape it as much as possible while the part is still joined to the bulk of the stock, then cut it free. The broken end of the scraper is filled flush for a good fit and the new tip is secured with epoxy.
Tractor:
1. The missing exhaust stack is easy. I drill a hole (size determined by the diameter of replacement part) where the old stack was on the hood. The old stack was 1/16 (.375) of an inch in diameter and I used some aluminum tubing of the same size. Place a dab of epoxy in the hole and insert tubing in hole. I placed some putty on the under side to hold the stack at the right height and to keep it straight. Once the epoxy set, I removed the putty (from the underside) and placed a drop of epoxy on the top of the stack to make the round over.
3. The driver was the hardest part. Maybe I'm just confusing hardest with most time consuming part of the project. The driver that closest matched the one on the cat (in scale and appearance) was one from a #43 Aveling Barford Tractor Shovel. The main issue with this driver is that it is cast as part of the base on that model and is quite "involved" with the seat and driver cockpit of the tractor. I used a busted up #43 and cut the driver free from most of the base. Then began a slow laborious process of carving away all the excess metal and saving only the driver and seat. I had to be careful how I held the driver as attempting to place a clamp of any kind (on the driver) either damaged the driver or blocked too much of the areas needing to be carved away.
I ended up holding the driver part using a 10 mil rubber glove (to give extra grip) and carving away using small diamond de-burring bits (with my Dremel). Since the tiny driver would heat up quickly, I had to keep dipping into a cup of water to quickly cool it down. The first time I did this, the moisture made a lubricant that kept me from holding the driver tightly. This is the point where I spent twenty minutes searching for the driver that was flung from the grasp of my wet gloved fingers. Once i found the driver, I sprayed the fingers of my gloves with some spray contact adhesive. This gave my gloves the needed extra grip to hang onto the driver after cooling it. The remainder of the carving went along without further incldent. The finished driver was joined using epoxy.
It's rainy here now and is forecast to last at least another day. So I am getting every thing ready for painting as soon as the weather clears. I'll show more photos as soon as it's painted. As always, if others have done this or similar tasks in a different way, I'm always eager to hear about your methods. Click on thumb nails to enlarge images.
Scraper body:
1. The pin which allows the scraper body to hook onto the tractor was broken off flush. I cut a short piece of steel rod and placed it into my drill (to make a mini lathe). While turning the rod, I used a small file to make the round over on one end. Next, I used a pin vice to drill out a small hole (the same size as the now shaped rod) where the connecting pin used to be. Test fit the pin, cut to right length and secure in hole with epoxy.
2. I fashioned a new upper half of the bed raise/lower lever using a scrap of plastic laminate. I shape the plastic, while leaving the part I'm making, connected to the bulk of plastic at what will be the base of the leaver. This allows me to work with a small shaped part while holding on to a much larger amount of material. When I'm happy with the shape of the part, I cut it free at the base. A trial fit or two determines how tall it needs to be (shortened by removing excess from the base while holding the part with needle nose pliers). The remains of the old lever are filled off leaving a nice flat spot for the new part. Secure the new part in place with epoxy.
3. The push point was fashioned out of a small piece of aluminum. I shape it as much as possible while the part is still joined to the bulk of the stock, then cut it free. The broken end of the scraper is filled flush for a good fit and the new tip is secured with epoxy.
Tractor:
1. The missing exhaust stack is easy. I drill a hole (size determined by the diameter of replacement part) where the old stack was on the hood. The old stack was 1/16 (.375) of an inch in diameter and I used some aluminum tubing of the same size. Place a dab of epoxy in the hole and insert tubing in hole. I placed some putty on the under side to hold the stack at the right height and to keep it straight. Once the epoxy set, I removed the putty (from the underside) and placed a drop of epoxy on the top of the stack to make the round over.
3. The driver was the hardest part. Maybe I'm just confusing hardest with most time consuming part of the project. The driver that closest matched the one on the cat (in scale and appearance) was one from a #43 Aveling Barford Tractor Shovel. The main issue with this driver is that it is cast as part of the base on that model and is quite "involved" with the seat and driver cockpit of the tractor. I used a busted up #43 and cut the driver free from most of the base. Then began a slow laborious process of carving away all the excess metal and saving only the driver and seat. I had to be careful how I held the driver as attempting to place a clamp of any kind (on the driver) either damaged the driver or blocked too much of the areas needing to be carved away.
I ended up holding the driver part using a 10 mil rubber glove (to give extra grip) and carving away using small diamond de-burring bits (with my Dremel). Since the tiny driver would heat up quickly, I had to keep dipping into a cup of water to quickly cool it down. The first time I did this, the moisture made a lubricant that kept me from holding the driver tightly. This is the point where I spent twenty minutes searching for the driver that was flung from the grasp of my wet gloved fingers. Once i found the driver, I sprayed the fingers of my gloves with some spray contact adhesive. This gave my gloves the needed extra grip to hang onto the driver after cooling it. The remainder of the carving went along without further incldent. The finished driver was joined using epoxy.
It's rainy here now and is forecast to last at least another day. So I am getting every thing ready for painting as soon as the weather clears. I'll show more photos as soon as it's painted. As always, if others have done this or similar tasks in a different way, I'm always eager to hear about your methods. Click on thumb nails to enlarge images.