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Cheap and Dirty Mid-Engine Truck

Here's another idea inspired by Junkyard Wars/Scrapheap Challenge
  (+3, -5)
(+3, -5)
  [vote for,

So I was thinking the other day about an easy way to make a truck mid-engined for better weight distribution. Lots of racing 4x4's (monster trucks, trophy trucks) have a mid-mounted engine, and instead of making a custom setup, here's what I came up with:

Take any body-on-frame 4x4 and strip it down to the frame and axles. Move the engine, transmission, and transfer case backwards a few feet, leaving the axles and suspension alone. Now switch the places of the driveshafts. The rear driveshaft becomes the front driveshaft and the front one goes in back. The engine will be moved back a distance equal to the difference in the lengths of the driveshafts. This way, the driveshafts simply drop into place. Then put the bodywork back in place, either cutting holes for engine clearance or just moving the truck cab back behind the engine.

You would have to tweak the suspension a little to cope with the shifted weight, but the truck would now float over sand nearly as well as a rear-engine Baja Bug, but with four-wheel drive for better traction.

discontinuuity, Apr 02 2007

Truck Chassis http://www.off-road...tout/photo_12.html#
Note location of tailshaft of Transfer case near middle of chassis. [jhomrighaus, Apr 02 2007]


       I like it: it sort of suggests those awb drag cars from the '60's.   

       Some would say, however, that a project like this would have cost implications anyway, and that the cost of a pair of custom driveshafts wouldn't break the bank in the scheme of things. Bun anyway.
Ned_Ludd, Apr 02 2007

       You then end up with a truck that has one forward gear and 4-6 reverse gears, rear-wheel steering, and a live axle in front with independent suspension in back. Also, the seating area would be full of engine and the body would be on backwards.   

       The work required to fix all this would be equivalent to building the thing from scratch in the first place. And if you're going through all that trouble, you'll use a proper space-frame chassis, like all those trophy trucks and monster trucks use. (was [-], edited to [+-]; see anno below)
5th Earth, Apr 02 2007

       [5th], I think you're assuming he'd have to turn the engine around; [rasberry] just said to move the engine back and swap the drive shafts coming from the transfer case.   

       Running the cooling lines should be amusing.
elhigh, Apr 02 2007

       Isn't moving the engine back going to screw up the cargo capacity? I mean even if you have two cargo areas, one in front and one in back, that seems not as convenient as having one big one in back.   

       Oh, and what problem is this idea the solution to? Call me confused.
Galbinus_Caeli, Apr 02 2007

       One small problem is that on many trucks the end of the transfer case of the truck is already very close to the center of the vehicle as it is so doing this would really only move the engine back just a little bit.
jhomrighaus, Apr 02 2007

       [5th], your version could be achieved just by turning the driver's seat round.
david_scothern, Apr 02 2007

       The only problem would be the very steep driveshaft angle for the rear axle if you move the engine back behind the cab. as [jhom] pointed out, if you just move the engine back a little bit, you can greatly improve weight distribution and only have to hammer out the transmission tunnel and rebuild all the drivetrain mounts. But this is already a standard practice in many motorsports. A project I'm working on is a similar idea to this, but basically using the front output shaft of a transfer case to power the rear axle with the engine moved back to be slightly foward of the rear axle. It would be rear wheel drive only, but I intend it to be more of a street truck than an off-road truck. There's more to it than that, but thats my basic idea.
Hunter79764, Apr 02 2007

       [jhomrighaus], in the picture you linked to, it looks like the transfer case output is still about one or two feet forward of the truck's center. Even moving it back that little bit would change things.   

       [Galbinus_Caeli], my vision for the bodywork involved simply putting a truck cab at the very back of the frame and leaving the rest exposed. Of course, you could always put one or two truck beds on it for practicallity. There is no real practical application for this idea, except maybe in off-road racing. It just seemed like something you might see on Junkyard Wars, held together with tape and wire.
discontinuuity, Apr 02 2007

       Oh, so it wouldn't still try to be truck-shaped? Then I'd give you another bun if I could.   

       What about one of those funny looking delivery van cabs with the engine mounted underneath it? Place one of those on there and you might be able to retain a "normal" driving position on the truck.
Hunter79764, Apr 02 2007

       Corrections noted. The majority of the problems I originally pointed out are based on incorrect assumptions. However, I still think this method would put the engine squarely in the cab area, forcing a rework of the body and seating arrangements. Not as a big of a problem as my first interpretation, but still a bit of an issue. Vote changed to neutral.
5th Earth, Apr 03 2007

       Yes, you would need to cut out portions of the body work to fit the engine. But if you don't mind sharing cabin space with the engine, this is really no problem. Just watch out for broken fan belts!
discontinuuity, Apr 03 2007

       My understanding is the whole idea for this thing is for an off-road racer or just for funning. No practical considerations are required, so the usual necessities of useful load bed and uncompromised accomodations are off the board.   

       If you're going to take the enormous step of placing the engine abaft the cabin, then whatever other alterations you might make to accomodate that are simply another slice of the pie.   

       FWIW, you could do a super quick and dirty version of this by simply constructing a frame and bolting the engine to that, right in the bed. You wouldn't even have to move the tranny or transfer case. The engine does its thing in its new home, and power is routed via a Kevlar belt (think Harley Davidson cruisers) through the bed to a jackshaft under the truck, up to the input end of the tranny. It raises the CG to an uncomfortable height, but hey. We're just spitballin' here.   

       The clutch will be a little funky. To cope with the rotating mass, it may be best to have a hydraulic clutch on both the engine and the tranny, and split the line coming from the clutch master. The rest is just plumbing of fuel and cooling lines, some vacuum lines, simple stuff.   

       The suspension will be totally out of kilter with several hundred pounds missing from the nose.
elhigh, Apr 04 2007


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