Bike Rack for 21RBS

[charliem]

[font size="3"][font face="arial"]Added a 2 bike Swagman basket carrier to the rear of the 21RBS:

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Notice I had LL beef up the bumper to take the torque load of the 2" receiver and bike rack. Below is the drawing I gave LL and they did a beautiful job with it. The bikes, which my wife can see with the rear view camera  , ride with no observable motion. They feel very solid; they're low enough to easily load/unload; and high enough not to drag on gas station entrances.

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[tinkeringtechie]

Very interesting. So it looks like you told them exactly what to do. Did anyone at LL do some calculations to see if this approach would be structurally sound? If the stock frame rails are strong enough, then this might be an "upgrade" that some of us could weld on later. I wonder if the 2x4" bumper could hold this on it's own (with a chunk of 2x4" tube behind the bumper so the bracket would fit). Or maybe it doesn't have enough torsional rigidity.

[charliem]

[font size="3"][font face="arial"]They just followed my drawing exactly; no calcs or comments. [/font][/font][font size="3"][font face="arial"]The added 2x4 is welded to both the existing bumper AND each of the rails separately, not just to the existing bumper. [/font][/font][font size="3"][font face="arial"]The effect is to have two 2x4s laminated together and welded securely to the rails.  Note that LL offers an optional  rear platform that extends the rails 19 inches and puts the flooring across them. The rails are plenty strong.

The existing bumper MIGHT take the torque, but I wanted to be sure. LL and other mfgrs caution against racks on bumpers so I went the safe way. BTW I posted a mod on the RPOD forum where I modified the Swagman 2" receiver to fit a 2x3 rail, which could be done for this bumper, but I went this way because I could. There is room to have the add 2x4 welded on but, you'd have to do it as I've shown and you'd have to deal with the existing lights and wiring.
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[pinstriper]

Charlie,

We just bought a 14DBS, and I'd like your thoughts on how to get a small carrier added to the back - like the aluminum units you can get from Harbor Freight that pop into a hitch receiver. We'd want to have someplace to haul campfire wood, etc.

I haven't taken possession yet, so I haven't set any time into pondering it in detail.

[charliem]

[font size="3"][font face="arial"]First question is have you bought it yet? Has it been built yet? If you ordered it from the factory and it hasn't been built yet you can ask Livinlite to add the optional  rear platform. That is designed to do what you want, but must be designed in as they build it. If you bought an existing trailer off a dealer's lot the options are more limited. The bumper is not really designed for heavy or high torque loads. For light loads or loads that will be carried close to the back of the trailer you may be able to use a bolt on carrier such as available from Swagman. Very light bike racks for a single bike may be OK with a bolt on 1.25" receiver. I'd be very cautious with anything that requires a 2" receiver. The aluminum bumper is not designed for heavy loads. If you really need to carry something heavier I would suggest adding a second 2x4 inch tubular aluminum or steel member parallel to the existing bumper, but closer to the trailer body. [/font][/font][font size="3"][font face="arial"]Much like the design I illustrated in my post. [/font][/font][font size="3"][font face="arial"]This could be a  bolt on configuration, but must be bolted to the frame rails, not the existing bumper,[/font][/font][font size="3"][font face="arial"] [/font][/font][font size="3"][font face="arial"]using U bolts or flat plates with long bolts. It is important not to drill holes in the trailer frame or bumper. Give me a bit more info on your situation and your requirements and I'll try to help.
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[pinstriper]

We're buying off the lot. I wonder if the dealer can add something.

[charliem]

[font size="3"][font face="arial"]I'd be VERY careful with having the dealer "add" something. Sorry but I have a basic distrust of dealers. They have way too much skin in the game, so to speak. To really solve the problem you need someone with a basic understanding of structural engineering. The weak points in the existing bumper are the welds to the frame and the inherent torsional strength of the 2x4 bumper. Sorry for the engineer speak, but those are the facts. Any torsional load applied to the bumper puts the top frame welds in tension, which is the worst case for a weld. In other words, the bumper will just tear off the frame at those welds. If the welds don't fail the bumper itself may twist. Any solution must minimize this by adding frame attachments closer to the camper rear wall. [/font][/font][font size="3"][font face="arial"]I have seen a dealer solution that simply added a 2x4 doubler in the middle of the bumper, thus providing a 4x4 mounting for a 2 inch receiver. That's worse than no solution because you think you've done something. Remember that the rear of a trailer is a pretty rough environment. It's like the tip end of a whip. Lots of action and lots of force magnification. You might start by talking to the LL factory. They're really helpful folks and may be able to help.
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[tinkeringtechie]

I agree with Charlie on not having the dealer make any modifications... they may not have your best interest in mind.

So far all the concerns have been about structural integrity, but there's an equally important consideration that hasn't been mentioned yet: weight distribution and trailer sway

It's risky to add any significant amount of weight behind the axles (especially hanging off the back). Most weight should be above or in front of the axles to help keep the trailer stable. A couple bundles of firewood, or a bike or two shouldn't have too much effect, but I wouldn't put more than 50lbs or so back there without taking a trip to the scales. I would guess that every pound that hangs off the bumper reduces the tongue weight by about a pound, and if the tongue weight goes below 10%, the trailer might become unstable.

[charliem]

[quote source="/post/71/thread" timestamp="1394294811" author="@tinkeringtechie"]I agree with Charlie on not having the dealer make any modifications... they may not have your best interest in mind.

So far all the concerns have been about structural integrity, but there's an equally important consideration that hasn't been mentioned yet: weight distribution and trailer sway

It's risky to add any significant amount of weight behind the axles (especially hanging off the back). Most weight should be above or in front of the axles to help keep the trailer stable. A couple bundles of firewood, or a bike or two shouldn't have too much effect, but I wouldn't put more than 50lbs or so back there without taking a trip to the scales. I would guess that every pound that hangs off the bumper reduces the tongue weight by about a pound, and if the tongue weight goes below 10%, the trailer might become unstable.[/quote][font size="3"][font face="arial"]Of course you're absolutely correct. If you look at the geometry you'll see it's about a 2:1 ratio pounds added to  rear vs. pounds off the tongue. Even so it needs to be considered. In my case I was starting tongue heavy with 2 golf cart batteries, 2 propane bottles and a power jack on the tongue. I measured my tongue weight at #525  loaded for travel with full W/H, 1/2 fresh water, empty waste tanks, two bikes on rear and all the above on the tongue. Really nice of LL to put the fresh tank right over the axles. Tacoma tows nicely with the E2 WDH.[/font][font face="arial"]
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[tinkeringtechie]

With 525 on the tongue you should be fine. Just one of the golf cart batteries probably offset the bikes. The 2:1 ratio might be true for the 21'ers, but the geometry of the shorter camplites is pretty different. Pinstriper's 14dbs looks like the axles are much more in the center, so that ratio would be less generous. It might still work, but should be done only after some careful number crunching.

[charliem]

[quote source="/post/73/thread" timestamp="1394299958" author="@tinkeringtechie"]With 525 on the tongue you should be fine. Just one of the golf cart batteries probably offset the bikes. The 2:1 ratio might be true for the 21'ers, but the geometry of the shorter camplites is pretty different. Pinstriper's 14dbs looks like the axles are much more in the center, so that ratio would be less generous. It might still work, but should be done only after some careful number crunching.[/quote][font size="3"][font face="arial"]Oh Yeah! Guess I've got the 21 locked into my head. You're right, of course. I hope I didn't dump too much cold water on Pinstriper. [/font][/font]

[font size="3"][font face="arial"]And see my avatar for my new TV. Don't need no stinkin' WDH  [/font][/font]

[pinstriper]

I appreciate both of y'alls comments. Actually, I was hoping for something combining cold water to keep me from doing something stupid, and "don't tell me what I can't do, tell me how to do what I want to do", as the man in the movie said.

Since we're skating close to this, I was thinking of having the dealer (or me) change the battery rack to take two batteries. In case that helps.

[kycamper]

[font size="3"][font face="arial"]They just followed my drawing exactly; no calcs or comments. [/font][/font][font size="3"][font face="arial"]The added 2x4 is welded to both the existing bumper AND each of the rails separately, not just to the existing bumper. [/font][/font][font size="3"][font face="arial"]The effect is to have two 2x4s laminated together and welded securely to the rails.  Note that LL offers an optional  rear platform that extends the rails 19 inches and puts the flooring across them. The rails are plenty strong.

The existing bumper MIGHT take the torque, but I wanted to be sure. LL and other mfgrs caution against racks on bumpers so I went the safe way. BTW I posted a mod on the RPOD forum where I modified the Swagman 2" receiver to fit a 2x3 rail, which could be done for this bumper, but I went this way because I could. There is room to have the add 2x4 welded on but, you'd have to do it as I've shown and you'd have to deal with the existing lights and wiring.
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I want to install the Swagman as you have but 1) I'm concerned about voiding any warranty from LL and 2) "you have to deal with existing lights and wiring"?? Can you please explain what you mean by this??? Thanks. You did a nice job on this. Wish it came like that from the factory.

[charliem]

[quote timestamp="1394146490" source="/post/34/thread" author="@charliem"][font size="3"][font face="arial"]They just followed my drawing exactly; no calcs or comments. [/font][/font][font size="3"][font face="arial"]The added 2x4 is welded to both the existing bumper AND each of the rails separately, not just to the existing bumper. [/font][/font][font size="3"][font face="arial"]The effect is to have two 2x4s laminated together and welded securely to the rails.  Note that LL offers an optional  rear platform that extends the rails 19 inches and puts the flooring across them. The rails are plenty strong.

The existing bumper MIGHT take the torque, but I wanted to be sure. LL and other mfgrs caution against racks on bumpers so I went the safe way. BTW I posted a mod on the RPOD forum where I modified the Swagman 2" receiver to fit a 2x3 rail, which could be done for this bumper, but I went this way because I could. There is room to have the add 2x4 welded on but, you'd have to do it as I've shown and you'd have to deal with the existing lights and wiring.
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I want to install the Swagman as you have but 1) I'm concerned about voiding any warranty from LL and 2) "you have to deal with existing lights and wiring"?? Can you please explain what you mean by this??? Thanks. You did a nice job on this. Wish it came like that from the factory.[/quote][ol type="decimal"][li][font size="3"]I can't speak to the warranty issue. Warranties are primarily at the discretion of the supplier. They will make the first determination if it applies, but generally a mod in one place does not void coverage for other things in other places. That said, I'm not a lawyer and don't even play one on forums  .[/font][/li][li][font size="3"]When adding a bike rack to the existing bumper the first concern is the static and dynamic torque loads. I believe the weak link is the weld from the bumper to the frame. The welds and bumper member can handle the weight and twisting stress, but the welds may tear. I am an engineer, not a metallurgist or welding expert. I believe you might be able to have the second 2x4 tube welded on as I did, but the existing lights and wiring would be vulnerable. You would have to remove them before welding and reinstall them afterwards, but that doesn't seem impossible. There may also be a way to bolt on an additional cross member to the frame and add a longer receiver. The method of attachment would have to provide additional strength and torque resistance, not just thickness. I once saw a dealer applied fix that just added a metal 2x4 in the center so you could use a bike rack designed for a 4x4 bumper. The worst of the worst solutions. Buyer beware!
[/font][/li][li][font size="3"]Bike racks on the rear seem to be a common customer need so it would be nice if LL addressed them at the factory. That said, it's impossible to accommodate every upgrade and still sell for an affordable price. Hopefully this forum will suggest options that prospective customers can request. So far LL has been remarkably receptive to customization. I hope this continues.
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[gbpack]

Charlie - We came across this thread as we are about to purchase a 2" bumper mount (receiver) for our existing Swagman bike rack (that we normally use on the back of our Jeep). We would like to use this same bike rack on the back bumper of our 21BHS and would need to purchase the bumper mount receiver in order to accomplish this. We had LL reinforce the rear bumper of our trailer during the mfg process and it looks like they did a good job when adding the additional 2x4 of aluminum support beam behind the outside bumper (it's welded to both the rear bumper and the bumper support beams that stick out from the back of the trailer, both on top and underneath). So it looks like we should be OK to go ahead with our plan to now order the 2" bumper adapter for the bike rack, but wanted to check and make sure there wasn't something else that we need to do. Also, I assume that since everything is done correctly with the welding of the bumper support at the factory that our bumper should be reinforced adequately to handle the weight and torque load that will be placed on it by the bike rack and bikes. Is this correct? Do I need to check with the factory regarding what weight load our reinforced bumper is capable of handling, or should we be good to go?