Tri-dem "must Have Three Drivers..."

[Maxville Truck]

I Have a customer whom I will be putting a "silage/grain" hauling truck together for, They want a shorter turning radius in the fields but want the carrying capacity of 3 axles in the rear. What I propose to do is take a day cab ch613 with camelbacks and add a 3rd air axle driver to the rear of the tandems.

I know it sounds a little loony.. however this truck will need to "float" in questionable field conditions and the box will either be 24 or 26 feet long. so it will carry a lot of weight when loaded. A normal tag axle will only drag along. Thats why we thought drive the third one.

So here's my design thoughts and I'm looking for anyone here to pick it apart.

1. I will either use an air power divider on the front axle, or the automatic one.

2. I will definitely use an air power divide on the center axle (rear camelback)

3. standard rear axle in the rear (3rd axle)

4. the rear axle will be air which i will set up to dump the air so the weight fall to the camelback (front 2) for shorter turning, also when the air dumps the center power divide will kick in. ( THEY ORIGINALLY WANTED THE REAR AXLE TO LIFT BUT I FIGURED IT WOULD BE TO MUCH DRIVE LINE ANGLE.)

5. not sure how i should set the rear axle up... as far as ride height... I figured a leveling valve to begin with but, as the box gets full it will squat the camelback springs and cause the rear axle to fully inflate and take some pressure off the camel's, so now i'm thinking just set the pressure on a turn dial.

I'm enclosing a picture of one other truck i set up, it is a quad axle but it gets hung up in the fields...

I'm going to use the same wheel base minus the pusher. any input would be appreciated. :SMOKIE-LFT:

[theakerstwo]

I Have a customer whom I will be putting a "silage/grain" hauling truck together for, They want a shorter turning radius in the fields but want the carrying capacity of 3 axles in the rear. What I propose to do is take a day cab ch613 with camelbacks and add a 3rd air axle driver to the rear of the tandems.

I know it sounds a little loony.. however this truck will need to "float" in questionable field conditions and the box will either be 24 or 26 feet long. so it will carry a lot of weight when loaded. A normal tag axle will only drag along. Thats why we thought drive the third one.

So here's my design thoughts and I'm looking for anyone here to pick it apart.

1. I will either use an air power divider on the front axle, or the automatic one.

2. I will definitely use an air power divide on the center axle (rear camelback)

3. standard rear axle in the rear (3rd axle)

4. the rear axle will be air which i will set up to dump the air so the weight fall to the camelback (front 2) for shorter turning, also when the air dumps the center power divide will kick in. ( THEY ORIGINALLY WANTED THE REAR AXLE TO LIFT BUT I FIGURED IT WOULD BE TO MUCH DRIVE LINE ANGLE.)

5. not sure how i should set the rear axle up... as far as ride height... I figured a leveling valve to begin with but, as the box gets full it will squat the camelback springs and cause the rear axle to fully inflate and take some pressure off the camel's, so now i'm thinking just set the pressure on a turn dial.

I'm enclosing a picture of one other truck i set up, it is a quad axle but it gets hung up in the fields...

I'm going to use the same wheel base minus the pusher. any input would be appreciated. :SMOKIE-LFT:

Let me ask or comment on the ideal. Years ago i did a 3 axle all power set up but i knew it had to be a real chore in the start.

I used rockwell and peterbilt suspenion and one leveling valve so that was simple cause i could not lift one axle because when you lift any one of the axles it puts too much working angle on the ujoints and it will tear up too many things like the trans for one. On this set up they did not raise the 3rd axle anyway and i dont think you will ever be able to raise the 3rd axle with out pulling the drive line. If you can do it get a patten on it. I whent to a rockwell dealer and he looked up what i need and we only needed 1 power divider.It was on the middle unit and the front had a stright drive no prower devider and the back was a rear/ rear. I was told that the front would pull all time and the power would be divided between the front and the back 2 axles which they can divide the power between them self. I think i could have used a air lockout in front also but keep it lock all time and saved the money that the extra parts cost. The ujoint working angle is very importaint and if you need more infro on that i can scan sone for you to convince you that the angles have to stay within a rangle when the joint is turning. glenn

[HK Trucking]

How about building it as a quad, and use 2 camelback setups, and have 4 driving axles?

[Kav]

Hi Maxville. Why cant you set it up the same as the standard Australian Mack Trident with the Tri-drive which is used in the Northern Territory to pull four or five trailers. I think they use a fairly standard Air-bag suspension with two front through drive axles and one rear axle.- Michael

[bruiser]

Don't know what happened to my previous reply so if this happens to be redundant please forgive me. Have you considered using a steer axle from a 4 wheel drive? I realize what you were saying about dumping the air but not lifting the axle, it seems to me thats just asking for trouble the first time you high center that axle the only thing thats going to prevent it from rising is either the frame or the tires hitting the body.

[ThaddeusW]

Hmmm something like a Robinson drive mechanism would be perfect. I don't know if they are available here in the US but it works like this:

In the most simple configuration you have a leading drive axle and a trailing tag axle with normal tandem spacing. Both the drive and tag axle have dual tires. A simple friction wheel or sprocket is on a hinged arm with a hydraulic or air cylinder on each side between the axles. When you drive normally the truck is a 6x2 but if you need more traction you flip a switch and the friction sprockets are jammed between the tires transferring power from the drive tires to the tag tires giving you a simple 6x4 setup.

The Finnish truck company SISU (who used Mack engines) developed a tri axle setup called the Finn Bogie. It has a single planetary hub reduction axle with a leading self steering tag axle and a trailing dual tire lift axle. On the road both axles can be lifted when empty so the truck has only 2 axles on the road. When at the job site the rear tag is dropped to get the capacity of a tandem. After loading up you drop the leading tag to stay road legal and if you get stuck at the site just use the Robinson drive to get you free. Lighter and simpler than a tandem.

Here is the best picture of a Finn Bogie I could find:

I bet that Robinson drive would work just fine with a set of tandems too. Might even be able to fabricate a setup yourself.

Oh and I just read up that SISU does indeed have a tandem in which the rear drive axle is disconnected and lifted. Probably has some type of clutch between the front and rear drive axle.

Ah finally dug up the link to the Robinson drive system:

http://www.nurmiauto.fi/index.php?kat=36

Also has a pdf link that better illustrates the design.

[TandemB]

Maxville, years ago Diamond Reo built tri-drives used for cement mixer chassis. I used to have sales brochures but thats a long time ago. I also have seen some of these trucks in a truck junkyard in eastern Pa. I know where they are (if still there). Could call and ask and if over that way I could possibly take pictures. Tandem B

[theakerstwo]

Maxville, years ago Diamond Reo built tri-drives used for cement mixer chassis. I used to have sales brochures but thats a long time ago. I also have seen some of these trucks in a truck junkyard in eastern Pa. I know where they are (if still there). Could call and ask and if over that way I could possibly take pictures. Tandem B

I dont think they could raise 1 axle like he wants to do . I dont know how that is going to be done. glenn

[Packer]

Thad,

I looked that over and the PDF shows a very long spring (and an air bag?)

Pivot point would be front spring hanger and because of the air bag, the axles would tilt rather than lift.

(?)

Packer

[Coalbucket]

Here is a brochure of ROBSON Drive

http://www.vbg.dk/dk/products/robsondrive/...20_brochure.pdf

[Speed]

I'm also wondering about putting a four wheel drive front end back there;seems like as long as you're planning on a drive axle,it'd be even better to have one that can help the truck make tight turns in soft conditions. Maybe pull out all the stops and set it up with duals. I'm thinking it could be plumbed into an electric/hydraulic pump with electric control;the driver could easily shut it off so the rear axle doesn't steer unless he wants it to,like the set up used on "Monster Trucks". Come to think of it,the shops that supply those rigs can probably help with getting the right parts and setting 'em up for best operation.

Just an idea.

Speed

[ThaddeusW]

I'm also wondering about putting a four wheel drive front end back there;seems like as long as you're planning on a drive axle,it'd be even better to have one that can help the truck make tight turns in soft conditions. Maybe pull out all the stops and set it up with duals. I'm thinking it could be plumbed into an electric/hydraulic pump with electric control;the driver could easily shut it off so the rear axle doesn't steer unless he wants it to,like the set up used on "Monster Trucks". Come to think of it,the shops that supply those rigs can probably help with getting the right parts and setting 'em up for best operation.

Just an idea.

Speed

Hey speed,

The Oshkosh PLS 10x10 has a rear driving steer axle. I seen a picture of the side and there is a steering drive shaft running from the front tandem steer axles and that turns the rear axle. so the steering wheel turns the twin steer and the rear most axle.

[Speed]

That sounds like an interesting set up. What was it used for,cranes and that sorta stuff?

Speed

[ThaddeusW]

That sounds like an interesting set up. What was it used for,cranes and that sorta stuff?

Speed

Its a military truck that has a hook lift roll of system that can haul flat racks, fuel tanks, 20' containers, a concrete mixer, dump body, and a bitumen spreader used to make quick and dirty roads. Same as a regular hook lift roll off for dumpsters.

Here is a picture I found that shows the left rear axles:

The steering gear in between the two rear axles and you can see the shaft

[GearheadGrrrl]

I believe that's a NATO standard called the "DROPS" system that the British initiated. It's rather clever, and they can even pull a trailer with another module on it.

[nrs91]

yea thats tha DROPS system

how are twin steer trucks set up?

anybody have a diagram?

trying to design a twin steer land rover and possibly have a rear steer axle too

maybe the twin steer set up could be used to make the rear steer on this truck but it would be steering all the time...

thanks

Nick

[ThaddeusW]

yea thats tha DROPS system

how are twin steer trucks set up?

anybody have a diagram?

trying to design a twin steer land rover and possibly have a rear steer axle too

maybe the twin steer set up could be used to make the rear steer on this truck but it would be steering all the time...

thanks

Nick

I have been looking into the setup as well and I have seen two different methods. First I have seen a gear box that splits the steering column into two steering gear boxes. The second setup is a little hard to describe but I can try to draw it up in using my leet paint skillz, lol:

The front steering box is setup normally but the pitman extends upward as well. There is a link bar that runs to the second steering box. Now you can see three black bars that run between the three points of connection on the second steering box. They represent the distances between the steering gear shaft and the link bar(A) and the pitman arm and steering gear shaft (. The distance A is the same on both the front and rear pitman arms. But B is shorter than A on the rear pitman arm. This provides a reduction in the steering angle. The second steering box is probably a slave box that has two hydraulic lines running to the front box to provide assistance.

[Maxville Truck]

Well, I built it...

1994 Mack CH with a 12,000 front and mack taper leaf suspension in rear. we were going to put the air behind the taper leaf, but the power divide lock ended up not giving any suspension travel under the trunion tree, so we had to move the tandem back and redrill all the holes. we then proceded to mount a mack air suspension ahead of the taper leaf with its own leveling valve. the truck had a push axle on it when we got it, so I used the existing air controls for the air axle, I hooked the leveling valve to the down line (regulated) of the push axle, (so we could limit how much pressure the axle would have when loaded, i figured the taper leaf suspension would settle under a heavy load, and i didn't want the air axle leveling valve over compensating and taking too much weight off of the tandems) I hooked the push axle's lift line to the dump line of the leveling valve and also to the front power divide (via a check valve) only, this way if they want (for lord knows what?) they can steer on the back tandem but not have the front drive spin. We also have the option of lock all 3 axles with the front 2 having power divides.. the truck has an apron chain silage unloading box built in Ringle, WI, 24 feet long. We run a dry valve hydraulic pump off the front crankshaft. The truck is not fully completed, but is operational.... I will be posting pictures as soon as we are completed with it.. (I'm taking a much needed vacation this week in Vegas,) and they wanted to use it on "2nd" crop hay... If this works good we will be building a second one like it this fall.. :banana: :SMOKIE-LFT:

[ciw65]

Well, I built it...

1994 Mack CH with a 12,000 front and mack taper leaf suspension in rear. we were going to put the air behind the taper leaf, but the power divide lock ended up not giving any suspension travel under the trunion tree, so we had to move the tandem back and redrill all the holes. we then proceded to mount a mack air suspension ahead of the taper leaf with its own leveling valve. the truck had a push axle on it when we got it, so I used the existing air controls for the air axle, I hooked the leveling valve to the down line (regulated) of the push axle, (so we could limit how much pressure the axle would have when loaded, i figured the taper leaf suspension would settle under a heavy load, and i didn't want the air axle leveling valve over compensating and taking too much weight off of the tandems) I hooked the push axle's lift line to the dump line of the leveling valve and also to the front power divide (via a check valve) only, this way if they want (for lord knows what?) they can steer on the back tandem but not have the front drive spin. We also have the option of lock all 3 axles with the front 2 having power divides.. the truck has an apron chain silage unloading box built in Ringle, WI, 24 feet long. We run a dry valve hydraulic pump off the front crankshaft. The truck is not fully completed, but is operational.... I will be posting pictures as soon as we are completed with it.. (I'm taking a much needed vacation this week in Vegas,) and they wanted to use it on "2nd" crop hay... If this works good we will be building a second one like it this fall.. :banana: :SMOKIE-LFT:

Well done fella. I have been following this topic with interest. Am keen to see the pics.

[Maxville Truck]

Here 's the finished product..... We built the front bumper for it also, It has a live pump driven off the crankshaft also.... I will be posting a video to youtube when I get a chance.