ouR escaPOD mods

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I'm not a structural engineer and my degree is in physics but I have done a lot of engineering and managed structural engineers and construction projects quite a bit. So, I usually know enough to get by with simple beam analysis like this. The simplification is to assume that the frame is uniformly loaded, after that its pretty straightforward. 
I don't know that anyone has proactively reinforced their frame but at least one member has had a frame failure and it was at the rear axle where you would expect it to be. That was olddawgsrule and I think Lippert fixed his frame in that area by welding on another 4x2 tube under the existing one. 

That's what I'd do, take a piece of the same 4x2x0.1 inch material and weld it to the existing tube under the axle, then reattach the axle to that. That roughly triples the strength of the tube in that area. It would also act as a riser kit. Ditto in the front where the max stress is actually under the trailer box a bit not at the tongue itself. You don't need to run the tube very far forward of the axle or very far forward on the tongue, you can see from the diagram  that the stress drops off pretty fast. Sometime last year I did an estimate on where to start and stop the doubled tube, you could probably find it in a search.

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offgrid Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290	Post Options Post Reply Quote offgrid Report Post Quote Reply Topic: ouR escaPOD mods Posted: 19 Aug 2020 at 12:35pm
	I'm not a structural engineer and my degree is in physics but I have done a lot of engineering and managed structural engineers and construction projects quite a bit. So, I usually know enough to get by with simple beam analysis like this. The simplification is to assume that the frame is uniformly loaded, after that its pretty straightforward. I don't know that anyone has proactively reinforced their frame but at least one member has had a frame failure and it was at the rear axle where you would expect it to be. That was olddawgsrule and I think Lippert fixed his frame in that area by welding on another 4x2 tube under the existing one. That's what I'd do, take a piece of the same 4x2x0.1 inch material and weld it to the existing tube under the axle, then reattach the axle to that. That roughly triples the strength of the tube in that area. It would also act as a riser kit. Ditto in the front where the max stress is actually under the trailer box a bit not at the tongue itself. You don't need to run the tube very far forward of the axle or very far forward on the tongue, you can see from the diagram that the stress drops off pretty fast. Sometime last year I did an estimate on where to start and stop the doubled tube, you could probably find it in a search.
	1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold

DavMar Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 04 Aug 2017 Location: Lexington, NC Online Status: Offline Posts: 592	Post Options Post Reply Quote DavMar Report Post Quote Reply Posted: 19 Aug 2020 at 5:53pm
	offgrid, thanks for the information. As I said I would like to see a write up on a tongue and other frame modifications by someone before I tried to tackle the task. I would have no problem with the idea of rising the Pod 4" if you were to raise the frame under the axle though I might then look into new entrance steps to add a step. Or adding a section of box beam under the tongue as you suggested but it would sure be nice to know exactly the length and placement of the steel, ect. before a novice like myself would even attempted to contract with a welder to do this great modification.
	Dave & Marlene J with Zoey the wonder dog. 2017 Rpod 180 2016 Toyota Tacoma SR5 4x4 Lexington, NC

offgrid Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290	Post Options Post Reply Quote offgrid Report Post Quote Reply Posted: 19 Aug 2020 at 7:14pm
	Ok, I found my post from last fall on this. Looks like I suggested reinforcing with 2x2x0.1 tubes up front and 4x2x0.1's at the axle. Probably I was thinking that would keep the weight down and ground clearance higher in the front, plus the loading on the frame isn't as bad there as at the axle. The riser kit adds 3.5 inches anyway so the 4 inches is pretty much equivalent. Here it is: Ok, I ran the numbers for the combined beam case. The formula for adding two asymentrical shapes together turned out to be a little tricky. I assumed a uniformly loaded frame from the tongue to the rear of trailer beams and a 3800 lb total weight. That's not really right but it simplifies the problem quite a bit and its not terribly far off. That puts the two max stress points at the axle and at a point about 58 inches aft of the ball. The stress is about half as much at the 58 inch point as it is at the axle. I get a 2G load capacity factor at the axle and 4G at the 58 inch point when I add the 2x2x3/16 tube under the 4x2x0.1 tube. If it were me, I'd stack 2x2x0.1 tubes in the front and use 2x4x0.1 tubes at the axle. That bumps the safety factor up to about 3G at throughout. You should have room to add the 4 inch tubes, they will add roughly the same height to the trailer as the riser kit does. I would make the length of the axle area frame reinforcement pieces 66 inches long and start them 28 inches in front of the axle, ending 38 inches behind it. I would make the 2x2 tongue area reinforcement pieces 78 inches long and start them 18 inches back from the hitch, ending 8 ft behind it. Total weight increase would be about 80 lbs.
	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: 6288	Post Options Post Reply Quote StephenH Report Post Quote Reply Posted: 06 Nov 2020 at 12:35pm
	Thanks to John T, I now have a cross-brace under the floor of our RPod to prevent the problem John M. detailed. Since John T lives near me, he had a shop fabricate two tubes with end plates. Mine was sized to fit the space on our RPod. His is slightly longer. (again, let no two pods be built the same seems to apply). I cleaned it up and painted it. This morning I installed it. The shop put 5 holes in the mounting plates, but I only used 3 of them, thinking that it should be sufficient since this is to strengthen the floor, not carry the entire load. Here are a couple of pictures: This is a preventative measure. Our floor is still pretty good. This is to support it to hopefully prevent the problems John M. had. Ours supports the existing floor without the additional layer that the factory put on John M.'s 'Pod.
	StephenH Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS

GlueGuy Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 15 May 2017 Location: N. California Online Status: Offline Posts: 2628	Post Options Post Reply Quote GlueGuy Report Post Quote Reply Posted: 07 Nov 2020 at 9:31am
	StephenH, is that the area underneath the kitchen? Reason I ask is because that's exactly where we put our hide-a-spare, and because of the limited space, the spare tire pushes up very firmly against the floor. I'm thinking the hide-a-spare/spare tire pretty much accomplishes the same function?
	bp 2017 R-Pod 179 Hood River 2015 Ford F150 SuperCrew 4WD 3.5L Ecoboost

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: 6288	Post Options Post Reply Quote StephenH Report Post Quote Reply Posted: 07 Nov 2020 at 1:27pm
	Yes, that is the area. I expect that the hide-a-spare will serve the purpose with the exception that it is more flexible than the brace I installed. It can bounce some, but overall, if it is tight against the bottom, it will provide support.
	StephenH Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS

offgrid Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23 Jul 2018 Online Status: Offline Posts: 5290	Post Options Post Reply Quote offgrid Report Post Quote Reply Posted: 07 Nov 2020 at 3:56pm
	I think anything you do to carry some of the floor load over to the frame would take care of the issue. It’s not like its grossly under designed. The tire is going to be inflated to 50-60 psi so even 5 square inches of contact area would reduce the floor load by 250-300 lbs which should be plenty.
	1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold

JA-Pod Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 28 May 2019 Location: Raleigh NC Online Status: Offline Posts: 35	Post Options Post Reply Quote JA-Pod Report Post Quote Reply Posted: 09 Nov 2020 at 9:29pm
	A followup to StephenH, Installed the bar under the floor of my 179, although my floor was not having a sagging issue, it always seemed a bit soft, after installing the bar it is very solid, it was a good investment. Simple design, measure between the frame, the welder subtracted 1/8 inch to allow the bar to be maneuvered into place. there was 1/4 in difference between StephenH's bar and the one for my pod and as he said no two pods are the same! I installed it 15 in from the grey water tank support, just to the right of the left door frame. Thankyou John Marrucci, although you went through a fair amount of frustration with FR, you posting has helped a great deal.
	John & Allison R-Pod 179 (2017) Nissan Frontier SL V6 4.0 (2019)

Pod People Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Senior Member Joined: 22 Sep 2011 Location: Chapel Hill,NC Online Status: Offline Posts: 1066	Post Options Post Reply Quote Pod People Report Post Quote Reply Posted: 09 Nov 2020 at 9:37pm
	Thanks to all of you guys-I just sent my welder a design for our support. I will get it Thursday and install it in our 179. I made mine different by adding 2 short(16") going front to back as well. will post after installation Thanks for the idea and design-podders helping each other again! Vann
	Vann & Laura 2015 RPod 179

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: 6288	Post Options Post Reply Quote StephenH Report Post Quote Reply Posted: 09 Nov 2020 at 10:17pm
	John, It looks good. I also appreciate John Marucci's posting of his floor modification from Forest River. I think it is good to be proactive on this. I agree that the floor seems much more solid with the bar. I am looking forward to seeing the one you are having made Vann.
	StephenH Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS