Top of wheel at jounce?? Frame flex comparison..

ScottReb

Adventurer
Just a couple of questions for the group. Im looking at F550 and Ram5500 body builder. They show a measurement of "top of wheel @ jounce." The height of the tire above frame rail on Dodge (8.6") and the difference of tire height on the Ford (5.5"). Am I correct in assuming this a relatively good indicator of flame flex?? If so, since the 5500 shows the tire approx at frame height (assuming stock size), the Dodge has quit a bit more flex or twist.

Am I getting this right?? Im curious to see how high a sub fame with 3 pt mount will need to be above the frame rails and how much fender cut outs would be need. This all hypothetical at this point since I currently have neither. Just comparing the 2 trucks (only on this aspect:)).

Can anyone ER tell me about how much space between the shell and frame of the ER or GXV? I don't think ER uses a subframe, not sure about GXV. I believe Turtle V did.

Thanks
Scott
 

LoRoad

Adventurer
Not sure if this will help or not. But isn't this more an issue of suspension travel vs. frame flex? Most frames are designed to flex at some level, some greater, some less. But it is primarily the suspension which allows wheels/tires to move up and down, yes? If that's true, then what you would want to find out (and I think the manufacturer should be able to answer the question with a phone call) is maximum displacement. I can tell you that on SherpAlypto the manufacturers builders guide says that there needs to be 3" of clearance above max articulation.
 

ScottReb

Adventurer
Thanks LoRoad. Makes sense. The whole mounting is making my head spin. I won't be doing anything except questioning all you guys but it would be nice to wrap my head around it. There are a lot of opinions but very few who have built and used their covers for 10s of thousands of miles.
Obviously I'm hoping to use the ford or dodge platform vs COE like yourself but the same physics apply. Can you tell me how high BlissMobil is putting your subframe (or box in their case) above frame?? They don't use a subframe with the design of their cabin I'm guessing. Just as a reference.
Hoping an ER/GXV guy chimes in too.
 

LoRoad

Adventurer
Can you tell me how high BlissMobil is putting your subframe (or box in their case) above frame?? They don't use a subframe with the design of their cabin I'm guessing.

There is a subframe per the design:

Subframe.jpg

which appears to be 7.22 inches.
 

ScottReb

Adventurer
Thanks for the pic. It appears to be a 4 pt, 7.2" is to the top of the subframe. If thats 4" sub thats only 3.2". Im sure the BAE has a pretty rigid frame. I would have guessed more was required. Im going to contact ER and GXV and ask if they will give some specifics on their respective 3pt mounts.
 

LoRoad

Adventurer
It appears to be a 4 pt, 7.2" is to the top of the subframe. If thats 4" sub thats only 3.2". Im sure the BAE has a pretty rigid frame.

This might help visualize the situation.

Total truck BAE Rodney pic 1.jpg

According to the builders guide there should be a total of 8.5" clearance above the top of the frame rail (on the 6x6 which is what we have), and that that would leave a 'nominal' 3" of additional clearance to the top of the tire.

6600 - Tire Clearance.jpg

So while 7.22" isn't the 8.5" recommended, this does still leave 1.28" of additional clearance. While it's not the 3" they suggest for 'additional clearance' there's still a fair bit. Now this might sound crazy to some to leave an amount less than the 3" recommendation but only until you know that there is a hard stop on the frame which would keep the articulation from going any further.

This was deemed acceptable and Bliss added additional protection to the box and the tires by incorporating the buffer plate you see in the drawings.

Hope this helps.
 
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ScottReb

Adventurer
Ill probably end up with another Dodge as well. Figured there are more 550 then 5500 for info on the ER forum though.
 

incognito

Adventurer
HY again,

in fact i've wanted Dodge little flex frame. otherwise the cabover part of the camper will hit the cab if it too much flex in the rear or not enough space between the cab and the cabover. too much space between those 2 not good neither. What is good for offroad is suspension flex and less weight.keep the weight as low as possible
hope this helps
incognito
globalcamper.blogspot.ca
 

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