Relocating Spare Tire & Storage Trunk Carrier - R-pod Owners Forum

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podwerkz

Senior Member

Joined: 11 Mar 2019
Location: Texas
Online Status: Offline
Posts: 966

Topic: Relocating Spare Tire & Storage Trunk Carrier
Posted: 19 Apr 2021 at 4:29pm

Dang. I hope you have good insurance.

r･pod 171 gone but not forgotten!

Colt

Senior Member

Joined: 16 Nov 2019
Online Status: Offline
Posts: 383

Posted: 19 Apr 2021 at 4:56pm

WOW!

Weigh the original spare and tire mount. Measure the horizontal distance from the pin hole in the original hitch to the center of the tire. Multiply that by the weight of the tire/mount assembly. Then, divide that by the horizontal distance from the pin hole to the center of your hitch basket. THAT is the safe weight limit of the hitch for a load in the basket. I doubt it be as high as the weight of the basket alone. That huge lever arm the basket has against the OEM hitch is like adding a pipe to a wrench to loosen a bolt. Plus, a bouncing load can easily add 2x the force of a static load.

That long lever arm is why the frame WILL bend at the axle if you do that often enough. The stress flows in the frame to the axle where it is transferred to the ground. The max bending stress is at the axle; that cheater bar thing again.

Put your storage box inside the trailer over the axle. Do not exceed the Gross Weight limit of the trailer or axle.

I know this sounds harsh. I hope it is about as harsh as the bouncing generators and gas cans will be when it lets go on the interstate. This is not 1970s design engineering (there is no excess capacity). With computers, that frame can be sized to within a very few percent of design loads. You can be sure FR did so to get the trailer weight so low.

John
'16 R-Pod 180

offgrid

Senior Member

Joined: 23 Jul 2018
Online Status: Offline
Posts: 5290

Posted: 19 Apr 2021 at 6:04pm

There are no mandatory design limits for the structural forces over the road vehicles are required to withstand. I've looked. Best I've seen are recommendations for heavy trucks that they should be able to at withstand forces in the range of 2.75 to 3 g's. Light vehicles like cars and pickups are tossed around more so have to be higher. The actual design limits used are company proprietary.

In contrast, I've run the numbers on the rpod frame and it's under 2g's at the axle. You can get light and cheap, or you can get strong and heavy, or you could probably design something fancy like a unibody trailer box and get strong and light, but it wouldn't be cheap. But you can't get all three. Rpods are light and cheap, don't for a moment assume they are strong. They aren't.

1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

StephenH

podders Helping podders - pHp

Joined: 29 Nov 2015
Location: Wake Forest, NC
Online Status: Offline
Posts: 6289

Posted: 19 Apr 2021 at 6:20pm

Light -- Cheap -- Strong

Choose only two of the three. There is no alternative.

StephenH
Happy is the man that findeth wisdom,...

ouR escaPOD mods
Former RPod 179
Current Cherokee Grey Wolf 24 JS

Dirt Sifter View Drop Down

Senior Member

Joined: 30 Dec 2018
Location: Right side OR
Online Status: Offline
Posts: 170

Posted: 20 Apr 2021 at 12:45pm

aimsghali, this isn't an ego thing, its a safety thing. It is a safe bet you NEED to listen to the good advice and reasons behind it posted by the experienced members of this forum. I am not new to towing, but don't have near the experience of those who have cautioned you, and I can see nothing but trouble from your set up. Best of luck.

Greg n Deb 2020 195 HRE
'07 Tundra 5.7L., '17 Tacoma 3.5L. Both with tow packages
1 Puggle, 1 Chihuahua support staff

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podwerkz Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 11 Mar 2019 Location: Texas Online Status: Offline Posts: 966	Topic: Relocating Spare Tire & Storage Trunk Carrier Posted: 19 Apr 2021 at 4:29pm
	Dang. I hope you have good insurance.
	r･pod 171 gone but not forgotten!

Colt Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 16 Nov 2019 Online Status: Offline Posts: 383	Posted: 19 Apr 2021 at 4:56pm
	WOW! Weigh the original spare and tire mount. Measure the horizontal distance from the pin hole in the original hitch to the center of the tire. Multiply that by the weight of the tire/mount assembly. Then, divide that by the horizontal distance from the pin hole to the center of your hitch basket. THAT is the safe weight limit of the hitch for a load in the basket. I doubt it be as high as the weight of the basket alone. That huge lever arm the basket has against the OEM hitch is like adding a pipe to a wrench to loosen a bolt. Plus, a bouncing load can easily add 2x the force of a static load. That long lever arm is why the frame WILL bend at the axle if you do that often enough. The stress flows in the frame to the axle where it is transferred to the ground. The max bending stress is at the axle; that cheater bar thing again. Put your storage box inside the trailer over the axle. Do not exceed the Gross Weight limit of the trailer or axle. I know this sounds harsh. I hope it is about as harsh as the bouncing generators and gas cans will be when it lets go on the interstate. This is not 1970s design engineering (there is no excess capacity). With computers, that frame can be sized to within a very few percent of design loads. You can be sure FR did so to get the trailer weight so low.
	John '16 R-Pod 180

offgrid Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290	Posted: 19 Apr 2021 at 6:04pm
	There are no mandatory design limits for the structural forces over the road vehicles are required to withstand. I've looked. Best I've seen are recommendations for heavy trucks that they should be able to at withstand forces in the range of 2.75 to 3 g's. Light vehicles like cars and pickups are tossed around more so have to be higher. The actual design limits used are company proprietary. In contrast, I've run the numbers on the rpod frame and it's under 2g's at the axle. You can get light and cheap, or you can get strong and heavy, or you could probably design something fancy like a unibody trailer box and get strong and light, but it wouldn't be cheap. But you can't get all three. Rpods are light and cheap, don't for a moment assume they are strong. They aren't.
	1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold

StephenH Members Profile Send Private Message Find Members Posts Add to Buddy List podders Helping podders - pHp Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6289	Posted: 19 Apr 2021 at 6:20pm
	Light -- Cheap -- Strong Choose only two of the three. There is no alternative.
	StephenH Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS

Dirt Sifter Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 30 Dec 2018 Location: Right side OR Online Status: Offline Posts: 170	Posted: 20 Apr 2021 at 12:45pm
	aimsghali, this isn't an ego thing, its a safety thing. It is a safe bet you NEED to listen to the good advice and reasons behind it posted by the experienced members of this forum. I am not new to towing, but don't have near the experience of those who have cautioned you, and I can see nothing but trouble from your set up. Best of luck.
	Greg n Deb 2020 195 HRE '07 Tundra 5.7L., '17 Tacoma 3.5L. Both with tow packages 1 Puggle, 1 Chihuahua support staff