Math problem

[wereveriroam]

Hello everyone. I posted for the first time the other day and got several useful answers to my question. I now find that I'm in need of some more expert advice and would like to find out what you think. I'm aware that you need a certain minimum distance between your hitch and back of cab, that makes sense to me. I imagine that you'd take out your back window or worse when turning if that distance is to close.
However, I have yet to find a distance on how much length is too much from the center of the rear axle to back of truck. I'm looking at flatbed trucks and found one with an 11' bed, it's 48" from center of rear axle to bumper. My concern is that on a turn the back of the truck will do some major damage to the generator box area. It seems most trucks have a 36"ish measurement here.
I took some measurements and think it will barely work. Since I screw up every now and then I'm wondering if I may have overlooked something. From the pin it's 6' to the generator box in a straight line. Now imagine where these lines intersect > to be the pin, the distance to the end of the legs is 7'6". I know there's got to be a formula to figure this but...
I'm thinking that the closet the corner of the bed will come to hitting the generator box is on a 45 degree turn since that's halfway to 90 degrees, after that the distance will increase. I'm thinking I'll have 6" of clearence? I see flatbeds come in just about every length, I know 9' & 10' work. Thanks!

[tquarles]

ok. You need 3 measurements and a couple simple calculations:

a: Measure the distance from the pin of the 5th wheel to the front of the generator box.
b: Measure the distance from the center of the axle to the rear-most point on the truck
c: Measure the overall width of the truck at the rear.

d: Compute c/2 - the distance from the centerline of the truck to the furthest out point on either side.
e: Compute sqrt( (b*b)+(d*d)) (long size of a right triangle - this is the distance from the centerline of the truck above the centerline of the axle to the corner point you picked measuring c)
f: Compre e to a - if e is greater than a, expect damage. If a is greater than e, you should clear at any angle. ALLOW A LITTLE EXTRA FOR SAFETY.

(it'll only be the 45 degree angle you speculated if b and d are the same).

[wereveriroam]

Quote:

Originally Posted by tquarles ok. You need 3 measurements and a couple simple calculations: a: Measure the distance from the pin of the 5th wheel to the front of the generator box. b: Measure the distance from the center of the axle to the rear-most point on the truck c: Measure the overall width of the truck at the rear. d: Compute c/2 - the distance from the centerline of the truck to the furthest out point on either side. e: Compute sqrt( (b*b)+(d*d)) (long size of a right triangle - this is the distance from the centerline of the truck above the centerline of the axle to the corner point you picked measuring c) f: Compre e to a - if e is greater than a, expect damage. If a is greater than e, you should clear at any angle. ALLOW A LITTLE EXTRA FOR SAFETY. (it'll only be the 45 degree angle you speculated if b and d are the same).

Thanks tquarles, your so helpful. I do have one question since my math didn't come out right. When I get to f: do I subtract the sum from e: (4560.25) from the inches of a: (72) which doesn't seem right or the square root of (72) which is (5184)?

[CD]

wereveriroam
It seems to me a much simpler method would be to use a tape measure and someone to help. If you are looking at the truck, lay out the pin location on the truck bed and measure from there to each corner. If I'm not mistaken the pin location should be about 2' forward of the rear axle. Hope this helps. If you can't use the truck, lay it out on the ground, floor etc.

[tquarles]

Your result in (e) is not a sum - it is the square root of a sum.
That is what you compare with your number from (a).

[wereveriroam]

Hey guys, I redid the math formula and the bed length will work but forget about accessing the generator box when hitched. CD I originally laid it out on the ground as you suggested (much simpliar IMO) and came up with the answer but didn't trust it. Thanks again!

[Ray,IN]

FWIW, some flat-bed trucks used for pulling a 5er or gooseneck trailer have bed corners mitered at 45* to increase turning clearance.

[wa8yxm]

Suggestion.. Drive the truck without any load.. I know a few truck makers who put the axle too far back.. This means that they have great Cargo Carrying capacity (Which they are very quick to advertise) but if you are "Deadheading" with no load in the bed.. And the road is anything but clear and dry.

You go round a curve at highway speeds and "Clear and Dry" will NOT describe your underwear... Been there.. thankfully I had slowed enough to stay clean.

If you want to learn how a truck handles empty.. A suggestion

Enterprise Rent-a-car

Rent one for a day

[wereveriroam]

Thanks again guys for some more very useful knowledge and insight. I have been looking at flatbed & chassis, standard cab, stick shift F-450/550's with the older 7.3 Powerstroke. I'm on a budget and I'm just going to use the truck to move my trailer (full timer) from point A to B with very little daily driving. I'm looking for a 60" cab to center of rear axle but they're hard to find, most are 84". The flatbeds are very high off the ground and the length of the long bed is almost excessive. Now I'm figuring I'll take the bed off and put it on craigslist then buy a used pickup bed. Everyone tells me that the truck is overkill for what I'm going to use it for but I'd rather have way too much truck than not enough. I know my choice of a truck isn't perfect but it seems to be the best one for what I'm going to use it for.

[Ray,IN]

"Now I'm figuring I'll take the bed off and put it on craigslist then buy a used pickup bed."
Sounds like a good plan to me, you might even work out a trade with an equipment sales lot.