Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Fixing Aluminium Brackets to Vehicle Body

Fixing Aluminium Brackets to Vehicle Body

Fixing Aluminium Brackets to Vehicle Body

I would be grateful for some advice on how best to fix aluminium brackets (35mm x 100mm) to Promaster van. The brackets are used to support a large (25 kg) solar panel on the roof of the van. I am concerned about vibration, long term rubbing wear and electrolytic action of the dissimilar metals. I am thinking of using 2mm neoprene gasket between the van roof and the brackets, with stainless steel nylocked bolts. Is this the best method of fixing or can you suggest alternative methods ? Perhaps a Polyurethane adhesive ??

Thanks in advance

RE: Fixing Aluminium Brackets to Vehicle Body

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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

RE: Fixing Aluminium Brackets to Vehicle Body

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.

RE: Fixing Aluminium Brackets to Vehicle Body


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

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.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Fixing Aluminium Brackets to Vehicle Body

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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

RE: Fixing Aluminium Brackets to Vehicle Body

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.

RE: Fixing Aluminium Brackets to Vehicle Body

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.

RE: Fixing Aluminium Brackets to Vehicle Body

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 pipe

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close