HEMTT Steering Question

[P_W]

Hi guys, I've searched but did not find what I was looking for.

On a HEMTT, how is the steering hooked up? From what I've read, the steering is not full hydro and it has some sort of mechanical linkage, but how is that hooked up with the steering wheel in front of the axle?

Also, is it possible to use a manual transmission in a cab-forward truck like a HEMTT or are you stuck with autos?

Thanks a bunch.

 

[Jones]

From the steering wheel, the column runs to a 1:1 90 degree box pointed towards the 'wind tunnel'. Once inside the wind tunnel it goes into another 1:1 90 degree box and heads back and down to the steering box that controls steer axle #1.
Off of the steering box a control valve hydraulically tells a second steering box that controls steer axle #2 what to do.
The biggest problem with manual transmissions in FC situations is clutch and shift linkage. A hydraulic clutch gets you half way there but shift linkage is another story.

 

[BobS]

Shift linkage is extremly easy with the Morse kit.

Steering is also easy to connect both axles-3 hydraulic slave steering gears on the frame, right hand (for a LHD vehicle) steering knuckle mounted lever arms on both front drive axles, and a bellcrank linkage connected to these 2 right hand lever arms. With attention to the linkage ratios, you can easily obtain perfect Ackermann steer on both front axles.

The same basic idea was used in the 10 steering axle trailer I posted pics of a week or so ago. (The pic with the M60 on the trailer)

If you are doing a refit...it's a little more complicated.

Best regards,

Bob

ADDENDUM: http://www.eng-tips.com/viewthread.cfm?qid=54516 an engineering discussion thread on Twin Steer systems. FYI.

 

[P_W]

Thanks for the info guys, I think I understand it now. I looked at some HEMTT pictures and and finally realized that that was a steering shaft going to the pass. side framerail.