Penthouse support bolt broke, van roof collapsed...

[BrianW]

@Pete @boywonder do you have hardware details on the parts you used?

[boywonder]

Excellent modification badger...yes that joint is crying out to be in double-shear...




BrianW: The nylon saddle spacers are from McMaster Carr:


for 1/4" holes in the spacers: P/N 92842A400


if you are using 5/16" pivot bolts: P/N 92842A500 or just drill out the above P/N to 5/16" holes.


A pack of 25 spacers is $8.32 today.



You will need to remove 1/8" of material off of each of the two spacers between the bars..they are 1/4" thick each and you need the pair between the bars to be 1/4" total. Using two unmolested spacers on the outside of each tube plus the above shaved spacers between tubes you get.....1/4" outside spacer + 1" tube +1/4" for pair of center spacers + 1" tube + 1/4" inside spacer for a total of 2 3/4"......


So if you are using shoulder screws ( recommended) you'll need 2 3/4" length shoulders.



Pete bought 6mm socket head cap screws that were 75mm (3 in) long....they worked fine...technically they are .014" undersized (.236" vs .250" holes)....if you don't want to use shoulder screws then a 3" screw is needed for the above design.


*shoulder screw length is measured by the length of the shoulder; the screw threads add length.......socket head cap screw length is measured from under the head to the end of the threads.

[boywonder]

In an effort to determine why Pete's roof goes up/down so easy, Pete sent me one of his helper springs to measure.


I grabbed one of my helper springs (they are no longer used..sitting in a drawer...my solution here: https://www.sportsmobileforum.com/fo...gs-1084-8.html) ...and measured it as well


Pete's Spring:


1.920" OD
.250" wire dia
11.75" Free length
rate 52 lbs/in
23 active coils


My spring:


1.920 OD
.250 wire diameter
24" free length
rate 20 lbs/in
47 active coils


I ran these springs through an online spring calculator and got spring rates very similar to what I measured on my mill using a digital weight scale.


https://www.newcombspring.com/spring...ing-calculator


Interestingly, the spring calculator shows a max load of around 220 lbs for both springs before the spring starts yielding (takes a permanent set, gets shorter)....assuming the spring material is either hard drawn steel or music wire....a safe bet.


If we assume the above to be correct then for either spring or roof length the max load on the crossbars is 220 lbs x 2 =440 lbs (one each side)


If we blow off the max allowable load assumption above (usually a bad idea) ....then pete's spring is at around 288 lbs at solid height..fully squished...which is about 5.5" of compression.


In that case Pete's springs are exerting 288 lbs x 2 (one each side)= 576 lbs total.



What does all this mean?



Well....in Pete's case with a bare EB top his helper springs are exerting somewhere between 440-576lbs total when the top is down.


In my case, with an RB top and about 70 lbs of solar and yakima crossbars on the roof I'm applying more than double that force (around 600-700 lbs each side) using a custom designed gas spring/die spring setup to get the top to raise easily.


..so another 60-70 lbs on the roof requires a boatload more spring load when fully down to get the roof to lift easily.....if I wasn't so old and lazy I would figure out this relationship...

[Pete]

Originally Posted by boywonder

In an effort to determine why Pete's roof goes up/down so easy, Pete sent me one of his helper springs to measure.


I grabbed one of my helper springs (they are no longer used..sitting in a drawer...my solution here: https://www.sportsmobileforum.com/fo...gs-1084-8.html) ...and measured it as well


Pete's Spring:


1.920" OD
.250" wire dia
11.75" Free length
rate 52 lbs/in
23 active coils


My spring:


1.920 OD
.250 wire diameter
24" free length
rate 20 lbs/in
47 active coils


I ran these springs through an online spring calculator and got spring rates very similar to what I measured on my mill using a digital weight scale.


https://www.newcombspring.com/spring...ing-calculator


Interestingly, the spring calculator shows a max load of around 220 lbs for both springs before the spring starts yielding (takes a permanent set, gets shorter)....assuming the spring material is either hard drawn steel or music wire....a safe bet.


If we assume the above to be correct then for either spring or roof length the max load on the crossbars is 220 lbs x 2 =440 lbs (one each side)


If we blow off the max allowable load assumption above (usually a bad idea) ....then pete's spring is at around 288 lbs at solid height..fully squished...which is about 5.5" of compression.


In that case Pete's springs are exerting 288 lbs x 2 (one each side)= 576 lbs total.



What does all this mean?



Well....in Pete's case with a bare EB top his helper springs are exerting somewhere between 440-576lbs total when the top is down.


In my case, with an RB top and about 70 lbs of solar and yakima crossbars on the roof I'm applying more than double that force (around 600-700 lbs each side) using a custom designed gas spring/die spring setup to get the top to raise easily.


..so another 60-70 lbs on the roof requires a boatload more spring load when fully down to get the roof to lift easily.....if I wasn't so old and lazy I could figure out this relationship...

I wish more of this made sense to me!

Based on this analysis, to what do you attribute the ease in which my top goes up and down, as compared to others you have seen and worked on?

[boywonder]

Originally Posted by Pete

I wish more of this made sense to me!

Based on this analysis, to what do you attribute the ease in which my top goes up and down, as compared to others you have seen and worked on?

Pete: Just be happy your roof works great.


I think it's the shorter springs....and the fact that you have nothing on your roof......the only difference between your springs and mine is the length. Mine are 2 feet long and yours are a foot long. Cutting the length in half doubles the spring rate.


So your springs do nothing when you first pull the roof down, but then the spring load goes up fast once the crossbar gets to the spring..which helps a lot. Once you let me know how much space there is between the end of the spring and the crossbar I can post here what your actual final spring load is.



With the longer version of the springs to get a similar load at the end of stroke it would be too hard to pull the roof down at the beginning of it's travel.



I'm pretty sure that's why newer roofs come with shorter springs.

[Justgosurfin]

Originally Posted by boywonder

Pete: Just be happy your roof works great.


I think it's the shorter springs....and the fact that you have nothing on your roof......the only difference between your springs and mine is the length. Mine are 2 feet long and yours are a foot long. Cutting the length in half doubles the spring rate.


So your springs do nothing when you first pull the roof down, but then the spring load goes up fast once the crossbar gets to the spring..which helps a lot. Once you let me know how much space there is between the end of the spring and the crossbar I can post here what your actual final spring load is.



With the longer version of the springs to get a similar load at the end of stroke it would be too hard to pull the roof down at the beginning of it's travel.



I'm pretty sure that's why newer roofs come with shorter springs.

Just jumping in here at the end. I’m about to put an EB top on my RB. Do you have any info posted about your custom spring/strut setup?

The nylons spacers seem like a great idea. Any tips to shave off the extra material evenly?

[boywonder]

Originally Posted by Justgosurfin

Just jumping in here at the end. I’m about to put an EB top on my RB.

AndrewST did an EB top on an RB....in case you are not aware of his thread...


https://www.sportsmobileforum.com/fo...s-v2-9841.html

Originally Posted by Justgosurfin

Do you have any info posted about your custom spring/strut setup?

Yes...it's here:

https://www.sportsmobileforum.com/fo...gs-1084-8.html

Originally Posted by Justgosurfin

The nylons spacers seem like a great idea. Any tips to shave off the extra material evenly?

Use a lathe.....


Short of that..you could sand them down with sandpaper on a flat surface

[Justgosurfin]

One day in a far away land I will have a huge garage with a lathe and welding equipment. Until that day my friends will continue to drink free beer in exchange for favors haha.

[boywonder]

Originally Posted by boywonder

Once you let me know how much space there is between the end of the spring and the crossbar I can post here what your actual final spring load is.

Catching up on the above question...Pete sent me a pic of the space between his crossbars and his helper springs.....and it's 4".


The slot in the roof rail for the crossbar to slide is 10" long and the crossbar uses most of that travel..so if we assume the actual crossbar travel is 9.5" (a reasonable assumption) then in Pete's case the springs are applying around 288 lbs on each side (fully compressed) or 576 lbs total based on the lengths and rates discussed above.


I'm applying more than double that force on my RB roof with solar pabels and Yakima crossbars......so adding stuff on the roof increases the spring load requirement on the crossbars dramatically.....as we already know...

[Justgosurfin]

Originally Posted by boywonder

Catching up on the above question...Pete sent me a pic of the space between his crossbars and his helper springs.....and it's 4".


The slot in the roof rail for the crossbar to slide is 10" long and the crossbar uses most of that travel..so if we assume the actual crossbar travel is 9.5" (a reasonable assumption) then in Pete's case the springs are applying around 288 lbs on each side (fully compressed) or 576 lbs total based on the lengths and rates discussed above.


I'm applying more than double that force on my RB roof with solar pabels and Yakima crossbars......so adding stuff on the roof increases the spring load requirement on the crossbars dramatically.....as we already know...

Boywonder, sent you a PM. I’ll try to get a list of questions together but I guess a big one right now is how large is the cut out for an RB top? Lengths of the side rails would be great to as I’ll need to shorten the EB rails a bit to get the crossmember where it needs to go above the B pillar.