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support for camper


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#11 JHanson

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Posted 23 October 2022 - 07:09 PM

Thanks to all who answer my question.  One more, a man I met this summer had put Summo spring on the front of his truck while having work done on the back.  His reason he hope to add wench and bumper at a later date.  What do all of you think of this set-up?  Will this work or would something else work better?

No. Tundras, as with most Toyota trucks, tend to be oversprung in the front. You'll likely not need any modification, but if you do, a proper uprated spring would be a far, far better choice.


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#12 ckent323

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Posted 23 October 2022 - 10:18 PM

My gratuitous thoughts

Think about how and where you will be using your rig and what your abilities are to repair problems.   All parts are subject to failure and I have read about far more failures of airbags than springs.  Also, all mods come with some changes in the OEM characteristics, e.g.  handling, ride, maintenance, etc.

If most or all of your use is on highway air bags may be a no brainer.

If you travel off road to remote locations think hard about the consequence of an airbag failure. 

I have driven the road to McCarthy as well as on other rougher off pavement roads such as to the top of Vincent Hill in the Blue Mountains of Oregon and numerous desert roads all over the Western US with my Dodge Clubcab Diesel W250 carrying a 2007 FWC Keystone camper on OEM leaf springs and Monroe Gas Magnum shocks. It was always a stiff ride but worse the front suspension bottomed out against the bump stops on the frame too easily.

This past year I upgraded to aftermarket Deaver leaf springs front and rear and Bilstein 51xx series shocks.  The new leaf springs are a bit softer than the OEM springs as well as lift the truck 2" higher than stock to give a bit most suspension travel (front axle travel was only 3/4" to the hard stops and is now 3").  The new springs work great but I was getting too much truck roll going around corners so I recently added a rear anti-sway bar which made a significant improvement and now there is much less roll around corners.  I am now happy with the overall result.

I am not familiar with the mods required for adding airbags to a Tundra so can't give specific advice but I urge you to be sure to think all the options through from a consequence of failure perspective before putting down your cash and implementing a mod.


I hope this is helpful,

 

Craig

 


Edited by ckent323, 24 October 2022 - 07:13 AM.

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1993 Dodge Cummins W-250 Club Cab long bed, 2007 FWC Keystone


#13 michelle_east_county

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Posted 25 October 2022 - 06:34 AM

I'm not a big fan of airbags except for people who take camper on and off. Air compresses as a geometric progression, whereas a spring compresses at a more linear rate (ignoring stepped or staged effect of overload leafs or variable rate coils). Many airbags are of a length and designed to only start to compress from normal ride height and if over-inflated relative to load, quickly support the load too firmly, feelng like a child's hippity-hop ball or over-inflated basketball. Shocks can't dampen them then.

But, assuming you're not actually using airbags to support a load beyond what the truck is rated for and instead only to better support and assust with an appropriate load, and don't have them over-inflated, some are OK IF support starts before (above) normal ride height. And, failure of an airbag may only mean an uncomfortable remaining trip where you go more slowly and carefully in places. The original springs are still there, so it's not like you'd be left by the side of the road as if an axle or main leaf broke.

Edited by michelle_east_county, 29 October 2022 - 04:46 PM.

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#14 ckent323

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Posted 31 October 2022 - 08:37 AM

ramblinChet,

I'm curious, where did trying to limit loads to 50% of payload capacity (GVWR-curb weight) come from?
 

As far as I am aware there are not many 3/4 ton pickups with payload capacities large enough to carry a fully outfitted FWC camper if the target was 50% of payload capacity, particularly 4wd diesel pickups.

A fully loaded FWC Grandby camper after filling with water, food, camping gear, house batteries, solar panels, awning and two people typically comes in well over 1500 pounds, likely closer to 2,000 pounds.  Based on targeting 50% payload that would mean the truck would need at least a 3000 pound to 4,000 pound payload capacity.  I think that is more than most 1 ton trucks have.  Indeed, the 100% payload capacity of most 3/4 trucks is reached or even exceeded at about 2000 pounds.  I do realize that there are domestic, 2WD, smaller gas engine, standard cab 3/4 ton pickups without weight adding options that have payload capacities well over 2000 pounds.

Am I misunderstanding what you wrote?


Edited by ckent323, 31 October 2022 - 09:03 AM.

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#15 ckent323

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Posted 02 November 2022 - 01:12 PM

Interesting.

 

I am not a mechanical engineer (rather Electro-Optical) but I have worked on a lot of mechanical hardware in the design and implementation stage during my 44 year aerospace engineering career.  To the best of my recollection most if not all of the mechanical items that I encountered were designed and tested with load margins of at least 150% and if critical 200% of rated load.  Indeed design margin was required and is standard engineering practice (even in Optical design).   I would be very surprised, shocked actually, if the GVWR on vehicles was based on only 100% load design or testing with no  margin.

I did a google search to see if I could find any info on truck manufacturer design margins for weight ratings and all I found is that axles often have margin built into their ratings to ensure they do not fail.

I did find the following relative to larger trucks (however, I suspect this also applies s to light duty trucks):

"Often, GVWR and gross vehicle weight (GVW) are thought to be the same, but they are not. A truck’s GVWR is the maximum weight rating established by the chassis manufacturer. GVW is the total weight of the truck and payload at a point in time.
 

There’s a common misconception that a truck’s GVWR is determined by adding gross axle weight ratings (GAWRs) together for all axles. Although this was a common way of calculating GVWR many years ago, it’s no longer an accurate method.

The chassis manufacturer task of establishing a vehicle GVWR is much more difficult today due to advancement of safety system standards and how vehicles meet these requirements. This is why many trucks have a GVWR much lower than the combined axle ratings. It’s not uncommon for a truck with a GVWR of 19,500 pounds to have a front axle rated at 7,500 pounds and a rear axle rated at 14,700 pounds.

Safety standards that apply to braking, vehicle stability, and chassis manufacturer internal standards for durability, dynamic stability and handling can restrict GVWR even though the sum of the axle ratings exceeds 22,000 pounds. In this instance, the OEM set the GVWR at 19,500 pounds based on test results and vehicle dynamic performance to ensure a safe, reliable truck.
 
A specific vehicle’s GCWR is based on parameters established by chassis manufacturers. The manufacturer makes an assessment in accordance with SAE International test protocols, determining maximum GCWR. Additionally, the OEM runs stringent tests based on internal requirements which may include testing total GCWR braking capability using only the towing vehicle chassis braking system. GCWR is the total weight of the truck pulling the trailer and the trailer itself. The truck chassis dictates proper GCWR for safe operation of the combination truck and trailer."

https://www.ntea.com...rk_trucks1.aspx

 

SAE J2807_202002 Performance Requirements for Determining Tow-Vehicle Gross Combination Weight Rating and Trailer Weight Rating establishes minimum performance criteria at GCWR and calculation methodology to determine tow-vehicle TWR for passenger cars, multipurpose passenger vehicles, and trucks. This includes all vehicles up to 14000 pounds GVWR.  This is a document that requires purchase so I cannot see the contents.
 

In absence of evidence to the contrary, I am confident vehicle manufacturers have margin in their designs and we can rely on the GVWR ratings of our trucks to determine safe loads. If this were not the case I suspect the potential liability to the manufacturers would be measured in very large dollar amounts.

I respect your opinion for the use of your truck but relative to a recommendation to others I think it errs on the far too cautious side.

If anyone reading is intimate with truck manufacturer design rules and design margins It would be most helpful to learn if there are standard practices or design rules relative to GVWR margin.

I hope this is helpful,

 

Craig


Edited by ckent323, 02 November 2022 - 01:26 PM.

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1993 Dodge Cummins W-250 Club Cab long bed, 2007 FWC Keystone


#16 michelle_east_county

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Posted 08 November 2022 - 05:33 AM

Another source for a working load for vehicles of about 50% of rated load capacity is how the vehicle will typically be used and optimizing spring rates for that. For a "half ton" truck (which, if a newer full-sized domestic, may mean up to a ton, including driver and passengers), a load up to about a half ton will ride and handle pretty OK, though better with a little less weight as manufacturers know most run around empty and are used for commuting. I recall Chrysler "K-cars" of early '80s were described in some car magazine or other of the time as being optimized for a driver and two passengers, which would have been about 50% of total payload capacity. Our 2020 F-350, Camper Package, 11,400 lb GVWR, 4,300 lb payload incl driver and passengers, rode empty much like an empty three-quarter ton truck of 25+ years ago due to high arch of rear springs being used to carry load and allow for lots of sag. TorqueLift Upper StableLoads (which engaged upper overload leafs constantly under load) helped with the 3,000 lb wet, loaded weight of Hallmark Ute but there was still porpoising after some dips, and some slow-motion wallowing. The truck was not at it's limits, was still safe enough to drive, but didn't feel solid and secure until one more leaf spring was added by Deaver Suspension in Santa Ana, CA, to each main leaf pack. I'd removed the TorqueLifts but Deaver actually would have been OK if I'd left them so compensated with a thicker spacer between main pack and upper overload, thus bringing them close to engagement with the camper on. Ride and handling is now more like the unmodified truck had less than a ton in the bed, and it corners pretty flat, with little wallowing. On gravel roads, the engaged upper overloads are a little rough but not bad, and smooth-road handling gains seem worth it. If I ever loaded truck to full rated capacity, it would more safely handle the load now than if as it was out of the factory. Empty load ride test is still pending but as I requested Deaver not firm it up like the proverbial lumber wagon, I expect it to at least be tolerable.

You can load vehicle to rated capacities and they may safely handle it, but not well, unless you do certain mods. As for going over that capacity, there is plenty of reserve to deal with the guy who occasionally loads too many blocks at Home Depot and not have a broken truck immediately, but if in a wreck there may be criminal penalties and loss of insurance coverage.

Edited by michelle_east_county, 08 November 2022 - 05:43 AM.

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