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|#846 - Cummins Swap|
|Author: andy1canada (Show all albums)|
Going to give this another try as my first attempt didn't go so well on the 'Diner-conversion' thread (Will update/edit that soon).
Started my Cummins swap by pulling off the bumper; only took better part of an hour. That sucker is HEAVY! Better part of a 100 lbs I bet. Will be looking to knock substantial weight off that baby while still retaining a 5000 lb towing standard.
This will take a while as it will unfold as time and resources permit, so please be patient.
More pics and hopefully some videos (FMC-TV) to follow.
To figure what I thought could be right place to weld the upper spring mount I decided to use the point on the chassis frame where the radius from the center of the torsion bar tube (center of rotation) out to the center of the air spring disk. Then it was a simple matter to transfer that distance up onto the chassis.
Forgive me my Cummin's brethren for I have sinned...all I had handy was some 'Caterpillar yellow' rust paint!
The bolt holes are more or less in a straight line on 4 1/4" centers. My laser came in handy for aligning the holes (which are also the centerline of the air-springs and the 3ft long mounting arms) which all had to position correctly (plumb) beneath the upper spring mount on the chassis. As is shown in the pics following, the 6" dia. circular 1/4" upper spring mount disc needs to be offset from the chassis beam enough to allow access to the mounting bolts and air-line hardware.
Here you can see the weld on the radius of the outer torsion bar tube. Had to grind off a bunch of what appeared to be asphalt black undercoating to expose clean steel.
Ignore the extra hole in this view; it was already in the beam material I used.
Added two 5/16" small gussets to the angle bracket to beef it up some. Drilled 3 x 11/16" holes for the 3 x 5/8" (gr.#8)bolts that will secure the air-spring mount arm to the mount. Note: I made the bolt holes 1/16" larger for two reasons (1)I'm not a machinist and only have a simple drill press to drill these holes in correct alignment and knew I'd be off a bit so this would provide some wiggle room. (2)slightly larger holes would also provide useful horizontal adjustment to help correctly align the lower spring mount with the upper one on the chassis. The following pics show the mount in place and the welding tracks where it's attached to the trailing arm.
Prep work on the trailing arm/torsion bar tube mount bracket footprint.
As Frank and Lenny and no doubt others have, I decided to mount the air-spring support on the trailing arm somehow. The road I took relies entirely on this 5/16" pc of angle iron being securely welded to the upper end of the trailing arm and to the outer torsion bar tube. This needed to be done right, so I hired a professional welder to do this particular job. All other parts I welded myself and as I am a woodworker by trade, I make no apologies for how sloppy many of the welds are.
Disclaimer: This is a sketch of the general idea of the direction I've gone with on this air-spring mod on my coach. Any sketches and all related pictures I'm sharing here on this subject are simply to provide my fellow coach owners with another perspective on an air-spring install on an FMC motorcoach. I am not in any way endorsing/suggesting/advising that this method will work, or, is safe to copy or use on other coaches. Anyone who does so, does so at their own risk.
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