Originally Posted by Daytonacoupe66
I am appreciative of suggestions on how much space to leave between the bottom of the fender and the top of the tire. I have no weight on the rear right now so expect the springs to compress somewhat when a bed is added. A few photos are included that depict approximately 7 3/4 inches for the stock fronts, but that looks like too much for the rear, so I'm looking at 6". Most of the photos I'm looking at have less space in the back than the front. At 6" I have approx. 1 3/4 inches from the top of the fender to the top of the rear shock mount. Any suggestions?
I also have to fab the fender brackets from scratch. I'm not finding many examples of the configuration of fender brackets mounted directly to the frame and see that a few of you have fabbed these up.
Never one to tell someone what to do, but usually willing to throw out some observations, so here goes. I think the dearth of frame-attached rear fenders is likely due to the huge suspension travel of the Mog, and the fact that any bed/ body has travel of its own, i.e. the potential is for the total travel above/ below the fender to be very large.
By way of starting point, I did some measures on my RW1, 7450 kg GVW. Sitting static in the shop, with partial tanks in a gutted/ rebuilt "camping" firebody (itself a Wackenhut original), I'd guesstimate the weight at 13,500-14,000 lbs, with a fair amount over the rear wheels. Tires are Conti 365/ R80 MPT's, with little wear. Firebody floor is 1/8" +/- (transmogrified when transshipped from a metric universe) aluminum.
Top of shock tower to bottom of floor plate 1 1/4"
Top of tire to bottom of floor plate 8 1/2"
Top of frame rail (at rear, level section) to bottom of floor plate 9 1/4"
Track width approx 90"
Width of rebound bump stop limit bumpers 34"
Static clearance/ travel room below rebound limiters 3 3/4"
The width ratio between limiters and track suggests a multiplier of about 2.6, which suggests that there resultant travel at the outer edge of the tire could be almost 10 inches. That would undoubtedly announce itself quite vociferously, so I am inclined to think there is a modifier at work, namely that the axle as a whole will move away from the body, as regulated by the pivot points of the Panhard rod, so as to achieve a balance of total upward force from the TWO springs as measured against the axle loaded weight. Long way of saying, the 8 1/2" clearly (so to speak) works, but good reason not to reduce that.
On to the frame flex/ body torsion side of the equation. The twist deflection limiter studs on the rear subframe crossmember are 16" outboard of the center of the truck frame, which is coincident with the pivot point of the subframe (what a surprise-super symmetry). One half of the track is 45", so there is a travel distance multiplier of 2.8. Measuring 1 7/8" of clearance at the frame bump stops/ studs suggest a theoretical possible downward travel of the firebody at the outer edge of the wheel of 5 1/4".
Lacking the ambition to pull out of the shop and find a large rock to surmount (the truck, not me), I have to mentally model the combination of spring compression and torsional twist in the firebody. I confess, the only thing I can definitively state is that I have wound the truck up a reasonable amount (but not to an extreme) and haven't scraped or bound up anything. What I am fairly confident of is that the suspension travel allowances on my truck are not to be reduced, and any fender on a similar Mog probably needs to respect those kind of clearances. It may be that , at least in some circumstances, the body will twist upward as the corresponding wheel rebounds upward; diverging rather than converging.
Another method of analysis is to look at the Atlas catalog, specifically their subframe and the fender liners they fabricate for use with. I have the Atlas subframe as a kit, but not yet assembled (time and money, natch). Michael Dennig told me the top of their subframe would be 75 mm lower than "standard", which is the amount they need the wheel well to intrude upward above the top of the subframe, to allow for wheel/ suspension travel. Their fender liners use all of that upside clearance, and are a subframe mount, NOT a frame mount.
A suggestion: do a real simple frame-fixed crossbar(s) mount for the new poly fenders, that will allow you to drive around now, and then do a snazzy subframe/ bed/ body mount when that becomes a reality.