dump truck with fifth wheel?

[Robo McDuff]

I am busy getting an M51A2, as explained in the linked thread.

Trying to figure out as much options as possible beforehand. Probably lots of people already did this, but does anybody has ever tried to make a dump truck - tractor combo?

Meaning, being able to take of the dump bed and install a fifht wheel and back? I saw it exsist in Canada (about 30 years ago) where some rig operators shifted between dump truck and tractor for logging operations depending on the season or demand. Not something to do every 5 minutes, but doable within one or two hours if you have a large enough machine shed or something similar (we do).

 

[m816]

The dump and the fifth wheel tractor are the same chassis.So it should be dooable.

 

[hndrsonj]

Yes, same chassis but that's alot of work. Trucks are relatively cheap just pick up a 818 also.

 

[hndrsonj]

Just saw your location, might not be so cheap i'm guessing.

 

[Robo McDuff]

Apart from that, Olga, my parter of 16 year, would kill me if I came home with two of them

The practical fact is also that I need a double registration inspection, once as dump truck and once as trailer, but that is not too bad, they just check if it is mounted correctly and copy the dimensions from the manuals.

 

[73m819]

When I worked at the quarry, we had dump come quite often , he had mounted a dump box over the fifth wheel, he said that could pull the box off in about 15 min., he had a A frame that he drove the dump under, raised the bed and secured it to the frame, he had legs that attached to the rear, then unpin the sub frame, use the hyd. to raise the sub frame (double axting cylinder), pin to bed, undo the hyd. quick disconnects and then drive away. I have seen the truck as a dump and as a tractor pulling a dump trailer

 

[Robo McDuff]

Ron, that sounds even better than I had in mind .

That means the hinges at the dump box should be mounted about 20 inches higher above the truck frame than normal to fit the dump box over the fifth wheel?

Any chance to a contact to that guy?

 

[Robo McDuff]

Just had a better look at the location of the hydralic system pushing the dump body up on DesertFox and Marcel's trucks. Those cylinders are located much farther backwards and attached to the dump body much farther back then I thought. I would expect that locating it more forward and attaching it more to the front of the dump body would be more efficient. You would need a telescopic hydraulic cylinder but it needs a lot less pressure to raise her.

Whatever, that location will be the biggest problem interfering with a permanent installed fifth wheel.

Busy on drawings, but the principle I am looking at is following:

1. The fifth wheel stays permanent in place (messing with that as "removable" probably would make the authorities go bananas).

2. Make a permanent subframe under the dump body to let the raised body rest on the frame. This needs some calculating to make sure that the weight distribution on the frame stays the same and the integrity of the dump body is not endangered.

3. Make a system to quickly free the connection of the hydraulic cylinders to the dump body.

4. Make a system to fold the cylinders backward or at least out of the way of the trailer body.

Desert Fox and Marcel, do you have some detailed pictures you could post or PM from the connection of the hydraulic cylinders to the main frame, and from the hinges in the back with the dump box raised?

Ron, do you remember or ever saw with the truck you mentioned how the cylinders were positioned with respect to the fifth wheel?

By the way, it should not be 20 inches but about 25 centimeters (10 inches) that the body has to be raised.

Ron again, this 43M20 converted to tractor you mention in your profile, did you do the converting yourself or you bought it like that?

 

[Robo McDuff]

Just found this site. Basically, the cargo assembly fits as a small wheel-less trailer over-on the fifth wheel.

Gave me some great ideas how to do this. For a cargo body, it would be a piece of cake. Unfortunately, for a dump truck a bit less; the fix of the hydraulic cylinders are the big problem in all ideas .

 

[73m819]

on the truck I talked about, the lift cylinder was at the front ,outside of the box, with the box built around it like a U, it attaches to the top of the tunnel and to the front of the sub frame, this type of lift cylinder setup is very common, with this type of set up, it allowed the sub frame to set on the frame with the fifth wheel between it, not sure if he used blocks, and/or a low profile 5th wheel

 

[kubota_247]

I might be totally missing the boat here, but couldn't you use a sigle axle or tandem axle dolly with a 5th wheel plate that has a lunette ring on the tongue and pull this with your dump truck. I've seen these in use but don't know any technicalities or legalities.

 

[Robo McDuff]

I might be totally missing the boat here, but couldn't you use a sigle axle or tandem axle dolly with a 5th wheel plate that has a lunette ring on the tongue and pull this with your dump truck. I've seen these in use but don't know any technicalities or legalities.

It's not common here in Europe, only in Finland and Sweden, and since a few years as trial in the EU with special combinations.

Another problem is that in Europe the dimensions of a tractor and trailer are limited. In the netherlands, the max length are as following

• single motorized vehicle (truck or trailer) 12 meters (39 feet 4)
• semi-trailer length also 12 meters, measured from the center of the king pin
• standard trailer also 12 meters

However, the problem is total overall length:
Semi tractor trailer combo: 16.5 meters or 54 ft 1
Truck trailer combo: 61 ft 2

This is measured from bumper to bumper. That's why Europeans mostly drive cab-overs and use tricks like retractable booms beteen truck and trailer. Sleepers for some time also used to be above the cabine instead of behind them.

 

[Robo McDuff]

As usually, I make it too complicated and also fail to do the 101 class before spekaing.

See the two pictures of the fifth wheel details. Now quite common in Europe: the fifht wheel assembly bolted onto a base plate. The base plate is bolted ONLY WITH FOUR BOLTS onto a slide rail. The slide rails is bolted outside onto the main frame with 12 bolts and sticking just above it.

Sliding the fifth wheel means loosening the base plate from the slide rails and shift the fifth wheel forward, backwards, or just take it off to make place for the dump body.

Which means I do not need special constructions to raise the dump body above the fifth wheel, I can just take it off (lifting it back up might take a bit more energy though).

Hydraulic cylinders. Have some ideas to get them out of the way, but have to see how they are really fitted onto the truck first.

Finally, a nice detail of a Czech tractor Honey, did you pick up the beer on the way home?

 

[Robo McDuff]

The dump and the fifth wheel tractor are the same chassis.So it should be dooable.

Just found something nasty. the dump truck has a DOUBLE FRAME or a subframe on top of the main frame. Did not notice that before.

Any idea how the second one is bolted on top of the first one?

Anybody knows if the hydraulic cylinder is connected to the subframe or to the main frame below it?

 

[73m819]

the sub and the dump come off as a unit, mounted with angle on the frame and sub

 

[Robo McDuff]

the sub and the dump come off as a unit, mounted with angle on the frame and sub

Tomorrow or Saturday I hope to take possession (keep your fingers crossed, hope the guy did not change his mind). Then I really can start working.

Ron, this sounds very interesting and promising, if the bolting to the main frame is not too complicated. That might mean that with four hydraulic support legs we could unbold the unit, raise it above the main frame, and drive the truck from underneath it, like they do with some cargo units. If so, and its a big if, that is certainly doable. I might even change -simplify the way the unit is bolted to the main frame.

The fifth wheel assembly I have solved in theory. That would combine perfect with the unit structure of the dump body. The sliding rails for the 5th wheel assembly here in Europe are normally bolted to the outside of the main frame (see earlier pictures) and stick a few centimeters above the frame. That actually might help centering the dump unit and help keep it in place.

Now its up to the registration guys to ask if they will accept such a switching unit as valid and put both things on the papers.

As I said, keep your fingers crossed.

 

[Robo McDuff]

It looks the dump body turns on hinges fixed to the subframe, as do the hydraulic cylinders.

The subframe is bolted to the main fraim with only 6 bolts per side. Four below the hinges (picture one) and two what looks like a spring connection at the front (picture 2).

That makes taking the dump unit off relatively easy.

The fifth wheel slide rails would fit along the upper part of the main frame, and the fifth wheel and base plate would be fixed to that with four bolts only.

Most important, the Dutch DOT equivalent sees no problem in giving both options on the registration papers:

Dump work, with empty weight x and total weight y, max towed z.
Tractor work, without dump body and subframe: empty weight is a, max semi-trailer towed weight is b.

Howewer, without a reliable source of better data on gross train weight, I might loose all my towing capacity.

 

[duncan]

For data, I would bet someone here could get you a copy of their american paperwork with gross vehicle weights, curb weights, etc on it. The DOT only needs a reliable reference.

 

[Scout]

I have not had a chance to read all the posts in the thread - but this is a concept that we have been wrestling with at work. We have a 10-wheeler, tri-axle with gobs of power, and an underpoweded tractor that doesn't see much use. We're toying with the idea of being able to swap the tri-axle dump body for a 5th wheel. I know of one contractor who has a truck set up like this - apparently he can go from dump truck to tractor in about 20 minutes. I have noticed recently that the NYS DOT has a system for thier trucks that can use one chassis with a dump body, salt body, or tractor. The tractor attachment has a subframe with a headache rack and 5th wheel attached. I've seen them at rest areas tilted back on two stilts - looks like they can swap bodies without any hoisting equipment, back under the propped-up body and drag it on. Can't for the life of me find any info online. It's got to be a manufactured product, it's not like the state is making them up themselves. I'll stop and see if I can get info off one next time I see one.

 

[Robo McDuff]

I once saw a system of how they fitted a swappable fifth wheel assembly on a truck. With some kind of click it in system, ready in a few minutes. Can not find the video back

Anyway, my concept for how this could work, after inspecting the truck more carefully, is following

Ideally, you need a system to raise and lower the truck about 8 - 10 inches. With air suspension, this would be a piece of cake. Since we don't have that, we will have to make four hydraulic legs that can easily attach to the truck or the dump bed. For the moment, we can also do that with two 10-ton hydraulic jacks under the truck.


Dump bed removal
1. Raise the WHOLE TRUCK about 8 inches (jacks, hydraulic legs, whatever I can figure out).

2. In front of the dump bed, there is an option for locking the front of the bed –left and right side– to the sub-frame. Lock that one.

3. Install support legs under the dump bed (drawings will follow later).
two legs will go under the tail of the dump bed.
two legs will go left and right front under the front of the dump bed.

4. Loosen and remove the six bolts on each side holding the sub-frame onto the main frame.

5. Loosen the link between the PTO and the hydraulic pump for the dump body (have to figure a quick way for that, maybe an electric pump would be the way to go)

6. Loosen the link between the operating lever in the cabin and the hydraulic pump. Electric pump with remote or wire controls would solve both problems.

7. Lower the truck. The legs will keep the dump bed high, and the truck can drive from underneath it. The subframe is hanging under the dump bed.

8. Reattaching the dump bed: do all in reverse order.

Fifth wheel assembly.
Quick and dirty: only a fifth wheel assembly, better would be a platform including the fifth wheel and base plate, plates to cover the frame space between the spare tire area and the fifth wheel, and the sliding ramps at the back.

As to fifth wheel, I now saw how they are attached to the frame (see pictures). No need to bother with a separate side rail bolted to the main frame. Just drill four or six holes directly into the top rail of the main frame and ready.

Basically the switching system could be the same as with the dump bed, but much lighter and hence easier. Just make a simple support leg system that holds the assembly high, drive the truck underneath it, and raise the truck.

You further need to add the electric connections and air connections for the trailer. This you can easily do as permanent fix, next to the spare tire. Just make a T connection on the air tanks, one to the back of the truck for your normal trailer, one to the spare wheel area for your semi.

I have to change the lighting anyway for the DoT requirements. I will install a new wiring for the lights and blinkers, so I can keep the original lights and switches functional as well. Quite easy to branch the wiring going to the back with a connection to the spare wheel area as well.

Easy on paper, now putting it in practice.