Using 80/20

Akor

New member
Hey all,
I am planning out my conversion and looking at a height adjustable bed using 8020 (either part 40-8020 or 1575) mounted to the pillars. Then mount the horizontal rails to support the bed to those. The only one I have seen done like this is from CreatiD https://creatid.com/news/sprinter-conversion-adjustable-bed-system/. He talks about rolling his rails to fit the contours of the van wall, anyone had experience with this or if the 8020 will match the contours when it is bolted into place? Also, will the curve of the van wall impact how the t-nuts will slide in the channel?
 

GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
Hey all,
I am planning out my conversion and looking at a height adjustable bed using 8020 (either part 40-8020 or 1575) mounted to the pillars. Then mount the horizontal rails to support the bed to those. The only one I have seen done like this is from CreatiD https://creatid.com/news/sprinter-conversion-adjustable-bed-system/. He talks about rolling his rails to fit the contours of the van wall, anyone had experience with this or if the 8020 will match the contours when it is bolted into place? Also, will the curve of the van wall impact how the t-nuts will slide in the channel?
Even 0.75" profile will not conform to the Sprinter wall curvature. 80/20 tends to be used in square applications. Hein did good work to get 1"x1/2" profiles to match rear doors curvature but this profile would likely be too weak for a bed weight. Go with Happy Jacks.
 

Oldrat

New member
Have a peek at a project 2000 bed
It lifts on seat belt type straps and has very little intrusion into the van space when sowed, unlike the legs of the Happijack

Link
 

Airtime

Well-known member
I've read through the whole long thread, thanks all for great contributions. One thing I was specifically looking for was info on what deflection is "strong enough." I saw the question asked a few times, but only answered in general terms, I did not see any quantitative examples.

What I'm looking for is some guidelines/rules of thumb that can be applied by a non-structural engineer. For example, carpenters can frame a wood house without calculating doing structural analysis of each stud or header. There are some basic rules that can be applied. How about for aluminum extrusions in a van? For example:
- Is 0.1" deflection OK or too much? What is a good rule of thumb to use?
- How many Gs should I use as a multiplier on weight? Is 3G vertical enough for road shocks? How about forward (crash) shocks?
- Should I assume "Supported 2 ends" or "Fixed 2 ends" in the deflection calculator if it is attached to vertical structural members? I assume the vertical members will have some flex, but which is closer to correct?

A specific example I have is a 100lb battery mounted on a shelf with a 39" span over the wheel well--it will see a lot of vertical shocks. Here is my current utility cabinet module--initially done in 15 series but looking at changing to 10 series. Note that the inverter will hang on a plywood sheet attached to the back, so the horizontal extrusions in the shelf will not carry that load. And this module will be bolted to the van wall and to the cabinet in front of it.
Utility cabinet.jpg
I'd like to minimize the height of the battery shelf above the wheel well. What size should the 39" structural members be? The load would be shared by two 39" extrusions. So if I assume 3Gs then each extrusion would see a 50 lb static load and up to a 150lb dynamic load. Also assuming a point center load (conservative), supported two ends, the deflection calculator gives me
- 1010-S: 0.14" static and 0.4"
- 1020-S: 0.02" static and 0.06" (strong direction), 0.07" static and 0.22" dynamic (weak direction)
- 1515-LS: 0.03" static and 0.1" dynamic

If I assume "Fixed 2 ends" then 1010-S would be 0.03" static and 0.1" dynamic, which seems good enough (?)

It's also worth noting that I will also have a 1/2" plywood shelf on top of the extrusions to support the battery--this would further stiffen the shelf. And in reality, the battery will be on one side not in the center. So in conclusion, my gut feeling (ungrounded in any deep structural engineering expertise) is that the 1010-S with a 1/2" plywood shelf should be strong enough.

Comments invited.
 

GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
I used 15 for practically all cabinets and work but my choice was driven by workshop simplicity and by minimum size requirement, a common denominator on the high strength requirements. Workshop simplicity means the same fasteners, screws, braces, connectors. In a few places I had to use 15 series for strength, specifically in sofa bed, so 15 became the common denominator.

I would use two support points for deflection analysis. I used 3G for vertical and horizontal loads.

In your case I think series 10 should be OK, you could add vertical support in the middle of battery shelf inside of the wheel well.

Mixing profiles sizes can get complex, so for me the choice of one size was good one. If I had to do many conversions, I would likely try to match size to required strength.

Good luck,

George.
 

99sport

Well-known member
Houses are sized for max deflection, in part, because people don't like walking on bouncy floors. Your battery wont complain. I suggest you look at the max stress. 8020 is 6061 with T5 temper - its ultimate tensile strength is 35,000 psi (often written 35 ksi). A general guideline is to keep stresses below UTS/1.4, so 25 ksi. Regarding the end constraints, you are right that it depends - how stiff is the structure you attach the end to? In reality it is somewhere between the free and fixed end constraints; using the free end constraints is more conservative.

Max allowable deflection is somewhat of a function of length - .25" deflection over the length of a wheel well is probably too much in aluminum - it might actually exceed the yield strength. I might shoot for .1". In addition to calculating stresses, my suggestion is to take a couple of lengths of the 8020 you are considering using, rest the ends on some 2x4s and set your battery on top, and maybe lean on it. Does the result scare you or are you satisfied with the deflection and stiffness. As you point out, this is worst case as it has no stiffening from the panel or end constraints, but it also doesn't include dynamic loads.

Also note when you use the calculator, that you have (approximately) a distributed, not a point load; you will get quite different results if you apply the 1000 pounds to the middle of the span vs near the supported end of the span. And one other comment, what is to stop you from using 4 or 5 beams of 1010 under your battery if it gets you the strength and stiffness you need without the additional size (which is precious in a small space)?

Edit, just looked at your picture and saw that you have 100 lbs of battery right up at the edge of the span. I'd absolutely use 1010 for that - if you build it and arent satisfied, add a couple more beams underneath as needed. Given the shape of the wheel wells, you could also add some diagonal corner braces underneath the battery if needed. Also, two vertical tubes halfway along the span joining the top and the bottom will stiffen things up if needed. (Build and test it in your garage prior to bolting into the vehicle).
 
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Airtime

Well-known member
I used 15 for practically all cabinets and work but my choice was driven by workshop simplicity and by minimum size requirement, a common denominator on the high strength requirements. Workshop simplicity means the same fasteners, screws, braces, connectors. In a few places I had to use 15 series for strength, specifically in sofa bed, so 15 became the common denominator.
Thanks George. My main driver is maximizing space. Every 1/2" adds up, so while I started out thinking to standardize on series 15 as you and some others have done, now I'm thinking series 10. I'm curious--if you had a need for strength in a few places, why did you not use stronger series 10 profiles (1020 for example) in those few places vs. making the whole build series 15? Then you could still have had the workshop simplicity.
 

OrioN

2008 2500 170" EXT
Thanks George. My main driver is maximizing space. Every 1/2" adds up, so while I started out thinking to standardize on series 15 as you and some others have done, now I'm thinking series 10. I'm curious--if you had a need for strength in a few places, why did you not use stronger series 10 profiles (1020 for example) in those few places vs. making the whole build series 15? Then you could still have had the workshop simplicity.
:popcorn:
 

Airtime

Well-known member
Houses are sized for max deflection, in part, because people don't like walking on bouncy floors. Your battery wont complain. I suggest you look at the max stress. 8020 is 6061 with T5 temper - its ultimate tensile strength is 35,000 psi (often written 35 ksi). A general guideline is to keep stresses below UTS/1.4, so 25 ksi. Regarding the end constraints, you are right that it depends - how stiff is the structure you attach the end to? In reality it is somewhere between the free and fixed end constraints; using the free end constraints is more conservative.

Max allowable deflection is somewhat of a function of length - .25" deflection over the length of a wheel well is probably too much in aluminum - it might actually exceed the yield strength. I might shoot for .1". In addition to calculating stresses, my suggestion is to take a couple of lengths of the 8020 you are considering using, rest the ends on some 2x4s and set your battery on top, and maybe lean on it. Does the result scare you or are you satisfied with the deflection and stiffness. As you point out, this is worst case as it has no stiffening from the panel or end constraints, but it also doesn't include dynamic loads.

Also note when you use the calculator, that you have (approximately) a distributed, not a point load; you will get quite different results if you apply the 1000 pounds to the middle of the span vs near the supported end of the span. And one other comment, what is to stop you from using 4 or 5 beams of 1010 under your battery if it gets you the strength and stiffness you need without the additional size (which is precious in a small space)?

Edit, just looked at your picture and saw that you have 100 lbs of battery right up at the edge of the span. I'd absolutely use 1010 for that - if you build it and arent satisfied, add a couple more beams underneath as needed. Given the shape of the wheel wells, you could also add some diagonal corner braces underneath the battery if needed. Also, two vertical tubes halfway along the span joining the top and the bottom will stiffen things up if needed. (Build and test it in your garage prior to bolting into the vehicle).
Thanks for the good tips. Yes there are several ways I could stiffen it a bit more if needed. I realized that because of the slope of the wheel well, 1020 would fit on the inner 39" extrusion. The outer extrusion will be attached to the wall so no need. Or as you said I could add more extrusions under that shelf to keep the height low.

I also found this supplier recommends 0.1" as a rule of thumb:
http://fandl8020.com/t-slot-aluminum-bar-use/

Based on that and on your and George's input it sounds like my guesses on deflection rules of thumb are reasonable:
- 0.1" max deflection
- 3Gs for acceleration
- Use "supported 2 ends" and center point load in the deflection calculator for default conservative estimates
 

Airtime

Well-known member
Not intending to stir the pot, I did read the whole thread. Just curious since I was just looking at use of 1020 myself on that battery shelf, vs. making that one part series 15 for strength.

I'll credit you with prodding me in another thread to look at series 10. After looking at this example and using that deflection tool, I think I will likely go with it. Thanks!
 

OrioN

2008 2500 170" EXT
I've read through the whole long thread, thanks all for great contributions. One thing I was specifically looking for was info on what deflection is "strong enough." I saw the question asked a few times, but only answered in general terms, I did not see any quantitative examples.

What I'm looking for is some guidelines/rules of thumb that can be applied by a non-structural engineer. For example, carpenters can frame a wood house without calculating doing structural analysis of each stud or header. There are some basic rules that can be applied. How about for aluminum extrusions in a van? For example:
- Is 0.1" deflection OK or too much? What is a good rule of thumb to use?
- How many Gs should I use as a multiplier on weight? Is 3G vertical enough for road shocks? How about forward (crash) shocks?
- Should I assume "Supported 2 ends" or "Fixed 2 ends" in the deflection calculator if it is attached to vertical structural members? I assume the vertical members will have some flex, but which is closer to correct?

A specific example I have is a 100lb battery mounted on a shelf with a 39" span over the wheel well--it will see a lot of vertical shocks. Here is my current utility cabinet module--initially done in 15 series but looking at changing to 10 series. Note that the inverter will hang on a plywood sheet attached to the back, so the horizontal extrusions in the shelf will not carry that load. And this module will be bolted to the van wall and to the cabinet in front of it.
View attachment 148806
I'd like to minimize the height of the battery shelf above the wheel well. What size should the 39" structural members be? The load would be shared by two 39" extrusions. So if I assume 3Gs then each extrusion would see a 50 lb static load and up to a 150lb dynamic load. Also assuming a point center load (conservative), supported two ends, the deflection calculator gives me
- 1010-S: 0.14" static and 0.4"
- 1020-S: 0.02" static and 0.06" (strong direction), 0.07" static and 0.22" dynamic (weak direction)
- 1515-LS: 0.03" static and 0.1" dynamic

If I assume "Fixed 2 ends" then 1010-S would be 0.03" static and 0.1" dynamic, which seems good enough (?)

It's also worth noting that I will also have a 1/2" plywood shelf on top of the extrusions to support the battery--this would further stiffen the shelf. And in reality, the battery will be on one side not in the center. So in conclusion, my gut feeling (ungrounded in any deep structural engineering expertise) is that the 1010-S with a 1/2" plywood shelf should be strong enough.

Comments invited.
Assuming it is not already there, a 3rd 39" 1010 rail-S rail between the front and rear ones could add the additional support.

However, the 1020 does give you the ability to have additional End Fasteners which would greatly reduce the chance of catastrophic failure at those points.
 
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Airtime

Well-known member
Assuming it is not already there, a 3rd 39" 1010 rail-S rail between the front and rear ones could add the additional support.

However, the 1020 does give you the ability to have additional End Fasteners which would greatly reduce the chance of catastrophic failure at those points.
Actually if I calculate as a variable load, centered 7" from the left, then deflection at 3Gs for 1010-S is 0.09". That said, this is one area I want really solid in a crash since having a lithium battery touch metal due to failed frame could be catastrophic. Your point about additional end fasteners is a good one. So I'll plan to do this:
- 1010 outer 39" extrusion bolted to chassis wall
- 1020 inner 39" extrusion for strength over wheel well

I also deleted a few smaller cross-members that seem superfluous, the shelves will have support along the long edges. Here it is:
Utility cabinet series 10.jpg
I'll continue in more detail on the rest of my design in my own build thread rather than here. But it's been very helpful to get some rules of thumb to use in determining where I will need more then just 1010.
 

Airtime

Well-known member
I'm comparing fasteners to decide what to use. I'm searching this thread finding bits and pieces. I looked at the 8020 site and I'll summarize my thoughts on what I think are three commonly used fasteners on this thread. As background, my approach will be driven by valuing my time over money. I plan to maximize use of cutting and machining services and minimize my shop/assembly time. So I will compare with machining fees.

Cost
- 4119 corner bracket - no machining - $3.78 total parts cost with hardware
- 3682 end connector - $1.60 part and 2 x $1.95 machining - $5.50 total
- 3662 anchor fastener - $3.30 part and $2.25 machining - $5.55 total

Strength
The anchor fastener and end connector are similar in strength, except that the end connector is stronger for torsional loads. The corner bracket is weaker in particular for cantilevered loads--which seems like would also be weaker for horizontal loads like racking during a hard deceleration like in a crash.

Versatility
The corner bracket seems most flexible as there is no machining. However it could interfere with panels.
The anchor fastener is reconfigurable along a T-slot
The end fastener is least flexible as it must line up with an access hole.

Overall my thinking is just to go with anchor fasteners. The corner bracket seems weaker for cantilevered loads, and actually does not cost that much less. I don't see any real advantage in end connectors--two machining operations, less flexibility, and same overall cost as anchor connectors. They are stronger torsionally, but I think I'm mainly concerned with vertical loads bouncing down a road, and horizontal loads in a crash.

Comments?
 

OrioN

2008 2500 170" EXT
I'm comparing fasteners to decide what to use. I'm searching this thread finding bits and pieces. I looked at the 8020 site and I'll summarize my thoughts on what I think are three commonly used fasteners on this thread. As background, my approach will be driven by valuing my time over money. I plan to maximize use of cutting and machining services and minimize my shop/assembly time. So I will compare with machining fees.

Cost
- 4119 corner bracket - no machining - $3.78 total parts cost with hardware
- 3682 end connector - $1.60 part and 2 x $1.95 machining - $5.50 total
- 3662 anchor fastener - $3.30 part and $2.25 machining - $5.55 total

Strength
The anchor fastener and end connector are similar in strength, except that the end connector is stronger for torsional loads. The corner bracket is weaker in particular for cantilevered loads--which seems like would also be weaker for horizontal loads like racking during a hard deceleration like in a crash.

Versatility
The corner bracket seems most flexible as there is no machining. However it could interfere with panels.
The anchor fastener is reconfigurable along a T-slot
The end fastener is least flexible as it must line up with an access hole.

Overall my thinking is just to go with anchor fasteners. The corner bracket seems weaker for cantilevered loads, and actually does not cost that much less. I don't see any real advantage in end connectors--two machining operations, less flexibility, and same overall cost as anchor connectors. They are stronger torsionally, but I think I'm mainly concerned with vertical loads bouncing down a road, and horizontal loads in a crash.

Comments?
I use End Fasteners first and foremost, and represent over 90% of my connections. Strongest, no issues with panels.

Lining up the access hole is simple, with purchasing and using the hole drilling tool.

If you want to save money, and not concerned with time, do your own tapping. Depending on the project, I tap.

Avoid 8020.net if you can due to their highest cost. I use Tnutz now and save over 50% on machining and tapping and they do not charge for cuts where 8020 is $2 per.

For my company needs, I buy bulk fasteners from China @ 10% the cost. (Metric works with 10 series)
 

GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
I used primarily corner brackets and end fasteners. For high stress I used anchor fasteners. Half wing end fasteners allow installation of a panel on one side without modification.

I extensively utilized 8020.net machining services to simplify my assembly work. Access holes drilling and some tapping for end connectors I did myself.
 

brownvan

2017 4X4 HR 144"
(I use the metric 40 series so most of my commentary is about that size; similar to the 15 series)
End connectors require a 7.1 mm access hole to access the fastener with a hex key and use a button head screw. So a 5 mm hex key for a M8 BHSCS
Anchor fasteners require the c'bore machining and ball-head hex key to access the socket head cap screw. So a 6 mm hex key for M8 SHCS.
I've used both in my van build as well as for work. I used to use the anchor fasteners predominantly but the end connectors are nice because all you need to do is drill that 7 mm hole and 8020 makes a nice jig for that. Sometimes have had accessibility issues getting a ball-head key to sufficiently crank down the screw in the anchor fastener. I personally think the end connector looks a little cleaner.
The various brackets & gussets available are also good options but I have tended to use them less and less with each new project. I also really like as much torsional stiffness as possible in my junctions when I'm using 8020.
 

brownvan

2017 4X4 HR 144"
I realized one other after thought. For a "bomber" tee-junction it is possible to use 2X anchor fasteners on opposing sides of the leg of the extrusion whereas you are limited to only use one end connector so there is an example of when you might want the max holding power and chose one over the other.
 

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