Adjusting the PH springs

[boywonder]

Originally Posted by BroncoHauler

Would the air cylinders just be for initial assist, or to assist holding the top up? I would hate to count on no leak-down issues for the top to stay up.
Herb

They would be for assist the whole way.....same as SMB electric Linak actuators. The extension springs are biasing the weight same as on a manual top.

....so next up is the three stage turbo booster gas spring.....15 1b, then 80 lb, then 2X 130 lbs for 260 lbs at the end of the travel when the roof is almost down. For reference, the SMB coil springs apply about 100-120lbs of force to the crossbars when the roof is down, so the 120 to 260 lbs (140 lb increase) helps when first lifting the roof.


I got the springs from McMaster; they are Suspa brand, but unforch the max force available in this size is 130 lbs......you could certainly go higher for the big force units at the end of the stroke.









This is the best solution yet (no surprise there).....and the roof can "rest" on the way down when it starts compressing the 80 lb springs and again when it's almost down it "rests" on the pair of 130 lb springs. Of course you can just pull it all the way down if desired. The two stop points are kinda handy when you need to "wiggle" the roof to get it to sit right when closed.


The action is way smoother, no spring sliding/grinding noises, and some nice controlled damping on the roof down travel.


I'm going to go with this setup for a while and see how it works out.


I have a few other ideas to reduce friction, like using LDPE for the sliding surface where the cross bar slides in the rear ceiling padded block, however this requires lots of disassembly of my solar panels etc..so that's something for another day.

[BUFFALO]

That sounds super nice! This is also a good solution for people that tend to carry gear on the roof and vary the loads based on activities.
A set of struts for your heavy kayaks. Swap in a lighter duty set for a couple pairs of snow skis in winter etc.

Would you mind sharing a rough cost estimate of the final setup?
And I think you said you had previously reinforced the helper spring backing plate?
Anything need modification with the strut setup there?

[boywonder]

Originally Posted by BUFFALO

Would you mind sharing a rough cost estimate of the final setup?
And I think you said you had previously reinforced the helper spring backing plate?
Anything need modification with the strut setup there?

I'm not using the SMB spring retainer plates at all now. I will likely fab some aluminum plates to cover the struts but haven't yet.


The gas springs are $14-$15 each...total of eight...so around $130-$140 for the parts including 6mm coupling nuts and delrin tubing. I had delrin stock in the garage that I used for the black blocks and little plunger noses that fit into the end of the crossbars.


The gas springs in there now are:


2 each 9415K16 15 lbs
2 each 9416K24 80 lbs
4 each 9416K14 130 lbs


https://www.mcmaster.com/#gas-springs/=1dtnt1c


Delrin tubing:


8627K239


https://www.mcmaster.com/#tubes-(mad...esin)/=1dtnupi


coupling nuts:


93590A106 (these are 18-8 stainless.....plain 'ole coupling nuts will work fine)


https://www.mcmaster.com/#coupling-nuts/=1dtnvdz


I've got another idea for the first few inches of roof travel...and will be ordering a few more things from Mcmaster to try it out. I slowly raised the roof while standing on a bathroom scale and the first few inches take around 150 lbs to raise...after that smooth easy sailing...so still attacking the inital up travel problem.


So far I've increased the max spring load from around 120 lbs (stock SMB springs) to around 340 lbs...and I'll keep going. (the 2X 130 lbs springs are 173 lbs each at the end of their stroke for 346 lbs total)....and with 4 chain links out of the extension springs they are applying another 400lbs of force when the roof is down.

[BUFFALO]

Thank you! Really appreciate all the work and sharing here.

[boywonder]

Here's the next round of modifications......


In an effort to get greater load at the very end of the roof travel (when the roof is down) I added some die springs for the last 1/2" of gas spring travel in the track.....this equates to around the last 4" or so of vertical roof travel.


These springs are very high spring rate and are used for opening dies/molds on large injection molding machines. The springs I'm using are 2.5" long and fit in a 1.25" bore and have a spring rate of 1176 lbs/in (wicked stiff!!!!). Usable spring travel is 40% or .5 inches..with a max load of 740 lbs at that displacement.


You can see the spring hanging out of the end of the assembly here.





These come in many sizes, lengths and load ratings and they are color coded Blue, Red, Gold or Green as you increase spring rate and load rating.


I drilled a hole in the end of the track channel and installed a sleeved socket head screw to pilot and retain the spring. At these loads you don't want the gas springs popping out of the channel when compressed. The opposite end of the assembly is fitted with a machined delrin "nose" that fits in the bottom of the crossbars.











Keeping in mind that the entire gas spring contraption will see the max load when the roof is closed (like 500-700 lbs)...it wasn't surprising that I had one fail where the 80 lb gas spring screws into the delrin block when the roof was almost down.....the assembly bowed a bit (I wasn't using the retainer plates above the channel) and the 6mm threads on the end of the cylinder ripped out of the delrin.


I subsequently replaced the delrin blocks with aluminum blocks to avoid this in the future. I also sized the aluminum blocks to fit in the channel and to be retained by the retainer plates.






I'm estimating that I'm loading the die springs to probably 500-550 lbs of so when the roof is down, as I'm not quite using the entire usable 1/2" travel of the spring.


This worked a bit better than the last setup but still needs significantly more force at the beginning of travel when lifting the roof from full down position.

[BUFFALO]

You are on a real mission! And have lots of creative ideas! I love it!
How much effort on your part is it now taking to lift the roof from the bottom?

[MountainBikeRoamer]

Scott! (Boywonder!)
Dude, you are an unstoppable creative madman these days!!!

Love the ingenuinity and stellar craftsmanship from you as always.
Definitely raising the art of the SMB penthouse with these innovations. (Haha, sorta pun there....raising the roof, lol....)

Can't wait to see some of this stuff in person.

[boywonder]

Originally Posted by MountainBikeRoamer

Definitely raising the art of the SMB penthouse with these innovations. (Haha, sorta pun there....raising the roof, lol....)

...let's go with raising the bar...


There are lots of nuances here that I'm glossing over a bit...like the trigonometric function of the spring travel compared to the roof height....and as I try stuff the behavior sometimes changes quite a bit..other things not so much.


I'm also mindful that I don't want to overload the tracks/rails at the rear of the van with the spring load; if my headliner wasn't all built out I would drill some holes and mount a stout aluminum block at the rear of the track to transfer the spring load through the sides of the track instead of the very end.


The large black plastic blocks holding the springs are presently UHMWPE (ultra high molecular weight polyethylene)...it's softer than delrin and way gummier to machine. I had that laying around, but I'll likely make delrin blocks for longer term use..as the 6mm gas spring threads in the block see the full load of 500-600 lbs.

[86Scotty]

Originally Posted by MountainBikeRoamer

Scott! (Boywonder!)
Dude, you are an unstoppable creative madman these days!!!

I don't think it's just 'these days', I think we're just getting to know Scott.

[Derek]

This is incredible work. I might just have to copy this once it's all figured out. I'll let someone else do the figuring out though. This is way above my knowledge.