Fixing Aluminium Brackets to Vehicle Body

• Jan 9, 2020

• #2

EdStainless

Materials

May 20, 2004

16,364

Waukesha WI USA

25kg panel on the roof while you are driving?
What makes you think that the brackets are nearly strong enough for the job?
You need to look into how the manufacturer attaches roof racks to this vehicle.
My guess is that they screw bolts through the roof into a threaded doubler plate.

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P.E. Metallurgy

 

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• Jan 9, 2020

• Thread starter
• #3

rixster

Geotechnical

Jan 9, 2020

3

GB

Thx for your comments. Perhaps I should expand a little....

There are 6 brackets each with 2 mounting holes. The M6 bolts will either be screw into rivnuts or into a spreader plate inside the van. The panel is 1.7m x 1m, so the weight/bracket(s) is evenly distributed. Also, as the panel is parallel (air gap approx 40mm) I don't think there is much wind loading as the moving air can pass freely over both upper and lower surfaces.

 

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• Jan 9, 2020

• #4

IRstuff

Aerospace

Jun 3, 2002

44,896

US

I don't think there is much wind loading as the moving air can pass freely over both upper and lower surfaces.

Click to expand...

Unless you've run CFD, that's just a wild a$$ guess; if the panel isn't absolutely parallel to the airflow, you've got a monster spoiler or wing, depending on its angle of attack. There's a reason why OEM solar panels are embedded in the roof. Moreover, because the airflow is a function of vehicle speed, the structure will have periodic loading, which makes the fastening system all the more critical.

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• Jan 9, 2020

• #5

EdStainless

Materials

May 20, 2004

16,364

Waukesha WI USA

And then there is the buffeting cross wind to deal with.
Any reason to not mount this 5-10mm from the roof and then add a fiberglass faring to blend it to the roof?
You might also need to tie the reinforcement plates in the roof together with some steel bracing.
I actually doubt that the standard frame for the solar panel will work in this application.
On the roof of my house the wind might be 60mph, on the roof of a van it could easily be >120mph (van + wind speeds) which would be roughly 4 times the mechanical loading.

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P.E. Metallurgy

 

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• Jan 9, 2020

• Thread starter
• #6

rixster

Geotechnical

Jan 9, 2020

3

GB

It was my intention to fit a spoiler and I think I better make it a priority...along with more sturdy fixings. Thx for your comments.

 

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• Jan 10, 2020

• #7

TugboatEng

Marine/Ocean

Nov 1, 2015

12,065

US

Lots of stuff to think about here. First, you need to attach to the structure that supports the roof and not the roof skin. Dissimilar metal corrosion is a minor issue. Bolting on to to rubber is rarely ideal as the rubber tends to extrude out from the joint before proper bolt tension is reached. Simply bolted joints are not water tight.

I personally prefer to use sealants over gaskets and use sealing washers under the bolt heads.

 

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• Jan 16, 2020

• #8

Guest

Any day now we'll see solar panels built into automotive spoilers, part of automakers' strategy to save the planet. Might as well put that extra aerodynamic drag to work

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

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