Dump to tractor conversion guide

Dump to tractor conversion for dummies
I talked about this in other threads, but thought it would be a good idea to put all steps in one post, so people can easily look back at it as a reference on how to do this. I ended up with FIVE pages of text, a bit long for one post. Here are only the main points and the pictures. The full text with all explanations and problems that can occur can be downloaded from our website (link under the pictures)

Warning
Trying to free these bolts might be problematic, be careful not to mess up your hands.




What you need to remove the dump bed
1. Spray can of WD 40 and a steel brush
2. Two bolt and nuts M10 - 8.8 high-grade steel. To bolt the dump bed to its subframe
3. Wrenches sizes 24, 26, and 29, best is the open-end-ring type. Get two of each.
4. Socket wrenches in 24, 26, 29.
5. Timber to lower the bed on: the pump which sticks out 10 inches below the unit.
6. A box to put in all your bolts, nuts, springs, rings, and whatever you took off and out.
7. A telescopic handler or crane able to manipulate at least 4,000 lbs at its tip.

Step one: 1-2 days BEFORE starting the real work.
8. Clean all bold and nuts and soak them in WD-40, which needs time to work.

Step two: make sure you have enough time and a good mood before you start.

Step three: the little things are easy to forget (with disastrous results)
9. Bolt the dump bed to the sub-frame.
10. Disconnect the levers to the hydraulic pump close to the pump.
11. Disconnect the pump from the drive shaft.
12. Tie the shaft with some rope or belt to the frame.
13. Disconnect the rear lights. They are connected to the sub-frame.

Step four: freeing the sub-frame with the bed in one go.
14. Front connection: remove the split pen out of the lower bolt.
15. Free the bolts and nuts.
16. Back connection: loosen the 4 bolts connecting subframe with the frame.
17. Take all bolts and nuts out and safe them in your box.

DO NOT DO THIS WITH THE DUMP BED RAISED BECAUSE IT SEEMS EASIER.



Step five: and now for the fun.
18. Connect four chains or heavy belts to the corners of the dump-bed
19. Raise the dump-bed unit SLOWLY an inch or so to get it loose from the main-frame
20. Check if all is really free, especially the connections to the hydraulic pump.
21. If not, lower the bed again and get it free.
22. If all is ok, raise the bed slowly, taking care not to damage the pump.
23. Use 4x4 timber to help maneuver the bed free
24. Lower the unit on the floor and make sure to keep the pump off the ground.
25. Take of the wooden spacer planks that was between the sub-frame and mainframe.



That is part one done. Time for one more cup of coffee for the road.

Creating an M52: adding the fifth wheel

What you need
1. A fifth wheel unit.
2. Buy high-grade NEW bolts and nuts to fix the 5th wheel to the frame.
3. Rent a professional magnetic drill.
4. Buy high-grade drilling oil.
5. Buy a high quality cutter bit.

Step 6: measuring: how to fix the 5th wheel. Take your time for this one!!!
There are two options:
I) Bolt side-rails to the main frame and then mount the unit onto the side rails.
II) Mount the unit directly onto the frame (which I did).

Option II: what I did
If the authorities agree (ask BEFORE you start), this one is the easier option.
6. If connected, disconnect the spacer plate from the actual 5th wheel assembly.
7. Measure how and where the unit will and can be connected to the main frame.
8. Fix the spacer plate onto the mainframe, make sure it is centered correctly.



Step seven: drill baby drill:
9. Make sure that you have good clean flat surfaces to position the drill on.
10. Line up the magnetic drill and switch on power and then the magnet.
11. CHECK IF THE MAGNET HOLDS AND SECURE THE MACHINE
12. Put a bit of cutting oil on the surface
13. Start drilling but DO NOT put a lot of pressure on the drill.
14. Every now and then, remove the steel thread coming off and add a bit of oil.
15. After each layer of steel perforated, stop and remove the residue material from the middle of the hollow drill.


Step eight: connecting the unit onto the main frame
16. Bolt the spacer plate onto the frame.
17. The nut for the middle bolt is hard to get at. Think of a solution BEFORE doing 16.
18. Bolt the fifth wheel onto the spacer plate.

That’s it. Piece of cake (phew). One we had the holes and knew the routine we managed to get the 5th wheel on and off in about 30 minutes.

We took the 5th wheel off again and put the dump bed back. No sweat.

really bad joo-joo to drill into a flange. always better to drill into a cross web, like the factory did.

drilling the web is stronger like Jaxsof said, but with the plate you mounted it should be fine. I would recommend putting those angle that were on the outside of the frame on too. great post by the way. I didn't see if you mentioned that the fifth wheel pin center should be 4" forward of the center of the axles. I can see that you positioned it right though.

jaxsof said:

really bad joo-joo to drill into a flange. always better to drill into a cross web, like the factory did.

Click to expand...

Just to be sure (like I said, its a guide for dummies ).
In US English terms, the top and bottom sections of a U-profile beam like used in the truck frame are called flange and the vertical section in between both flanges is the cross web?

The angle is the L-profile that in this specific case call I called the side rails?


Adding the side rails as originally used could have been the easiest way. Four problems with that in this case. The two pics on left show how a side rail is attached to the main frame in civil European trucks. Two pics on the right show how it is done with an M818 water trcuk I saw in a scrapyard in the Netherlands.

1. Getting those side-rails off the donor truck would have been a major pain; too many rivets and in hard-to-reach places.
2. This section of the M51 frame has already lot of rivets and connections in the cross web as well, so I would have to start cut holes into the side rails to go around those.
3. To get a good connection all along, the bolts for the side rails would have to be rather high in the cross web as well, away from its centerline.
4. The frame of the donor truck and that of the M51 differ about 1/2" in width. The old holes on the spacer plate would have been in the wrong position, but only a little bit so I would not be able to drill clean new holes for the new assembly in the spacer plate.

According the Dutch DoT, it is almost always forbidden to drill into a top or bottom flange. You can only drill around the center line of the cross web. Welding something onto a frame is absolutely forbiddden.

So I went with the pic above and some other detail pics to the DoT and to a company specialized in adapting civil trucks. Both came to the same conclusion that in this specific case my solution is OK. It is doable without significant loss of strenght because three of the five bolts go through both the frame and the cross beam, and the spacer plate itself adds strenth as well.

They actually recommended to use only 1 bolt at the rear side (left side of picture). Two would lessen the amount of solid steel between the two rivets too much. The five remaining bolts would be more than enough for connecting the unit to the truck.

Location of pin center. I was thinking including that, should have done so. You are correct, should be 4" forward of the center of the axles. You have some room there, which is used by those sliding fith-wheel units. In my case, the way the spacer plate fitted around the rivets put the center a fraction away from the optimum location. The DoT agreed that this difference was not enough to be bothered about or mention specially in the papers.

I also replaced the orginal pintle hook (illegal in the EU) with a certified fish-mouth trailer coupling.

The DoT said they would approve the construction as suggested and would calculate the max allowable tow load and GVW based upon the original specifications of the truck and of the used parts and the materials used. Once they said that, I started drilling. I am very glad they kept there promise and accepted the construction when I finally showed up there with the ready product.

According to the papers, the specifications now are:

Max loaded truck weight 42 500 lbs
Max trailer weight 68,500 lbs
Max semi-trailer weight 68,500 lbs
Max GVW 90,500 lbs

Yes, I know it's more than the original specifications (which are underrated). And to stall comments, no, no way I will ever go up to that max weight with these old brakes and engine (but it's nice to have it on paper).

My M931A2 Tractor is set up with the side rails on the frame that the 5th wheel bolts onto. I'd like to get a lower profile 5th wheel if possible that I may be able to nest under a bed so I could have the option of craning the bed off quick and exposing the 5th wheel. We'll see...it may end up being moved back the frame a little to lessen the angle the plate would need to be at since the truck is tall. Again, we'll see. Soon will have all my tractor parts off and for sale; spare tire holder and jib behind the cab mount dealie, 5th wheel, and rear ramps. Will pallet ship-