Metal strength advice

[Ringel05]

I picked up some new Viking Bags for my bike, have the one side drilled and mounted but it mounts through the rear fender trim. The problem is the trim (which is easily removable) is really not conducive to bolt mounting the bags. What I'm thinking is remover the trim and replace it with a 1/8" x 10" X 4" aluminum plate mounted to the fender with spacers.
What my question is is 1/8" aluminum strong enough to stand up to wind weight and vibration? Each bag's max recommended load is 11 pounds.

 

[fncceo]

I'm trying to picture this is my head ... the problem would seem to me to be ... not the strength of the aluminum mount ... but the fender to which it is mounted.

Fenders tend to be thin and flexible. They will bend and flex a lot more with the weight of bags on them.

How about an aluminum frame, attached to the bike frame, over the fender, and the bags are slung over that?

Along the lines of normal bike pannier mounts.

 

[Rambunctious]

I picked up some new Viking Bags for my bike, have the one side drilled and mounted but it mounts through the rear fender trim. The problem is the trim (which is easily removable) is really not conducive to bolt mounting the bags. What I'm thinking is remover the trim and replace it with a 1/8" x 10" X 4" aluminum plate mounted to the fender with spacers.
What my question is is 1/8" aluminum strong enough to stand up to wind weight and vibration? Each bag's max recommended load is 11 pounds.

What kind of bike?... I have a sportster and these are the bags I bought... I had a friend mount them and they don't bolt into my fender....

Harley Davidson Sportster Saddlebags. Hard & Leather Saddle Bags for Sportster - VikingBags

Shop best Harley Davidson Sportster saddlebags. The Viking lockable bike-specific aftermarket hard and leather saddle bags for Sportster motorcycles are durable, and retain shape.

www.vikingbags.com

 

[Ringel05]

I'm trying to picture this is my head ... the problem would seem to me to be ... not the strength of the aluminum mount ... but the fender to which it is mounted.

Fenders tend to be thin and flexible. They will bend and flex a lot more with the weight of bags on them.

How about an aluminum frame, attached to the bike frame, over the fender, and the bags are slung over that?

Along the lines of normal bike pannier mounts.

View attachment 664996

Motorcycle fenders are supported and not very flexible. Matter of the fact the nuts are mounted inside the fender along a reinforced steel band so it's not going anywhere. Heck the passenger seat is mounted on top of the rear fender.

Look at the side of the rear fender there's a chrome trim with two mounting points, that's what needs to come off.

 

[Ringel05]

What kind of bike?... I have a sportster and these are the bags I bought... I had a friend mount them and they don't bolt into my fender....

Harley Davidson Sportster Saddlebags. Hard & Leather Saddle Bags for Sportster - VikingBags

Shop best Harley Davidson Sportster saddlebags. The Viking lockable bike-specific aftermarket hard and leather saddle bags for Sportster motorcycles are durable, and retain shape.

www.vikingbags.com

You have throw-overs which is what I don't want, mine are leather covered hard bags.

 

[Rambunctious]

 

[fncceo]

That makes more sense...

An aluminum bar of the dimensions you describe attached to that fender where the trim is in that pic should do the job.

As the bike rolls from on side to another, if the bags are hanging free from the mounting bar, will they interfere with the wheel?

 

[Ringel05]

I know how to mount bags but in this instance the trim is a liability not an asset so let's get back to my original question and not try to over analyze it.
Will 1/8" thick aluminum plate be strong enough for what I want to do?

 

[fncceo]

I see now that the bags are rigid. For some reason, I pictured soft-bags, like throw overs.

 

[Ringel05]

That makes more sense...

An aluminum bar of the dimensions you describe attached to that fender where the trim is in that pic should do the job.

As the bike rolls from on side to another, if the bags are hanging free from the mounting bar, will they interfere with the wheel?

No, they will be solidly mounted and will not move.

 

[Ringel05]

I see now that the bags are rigid. For some reason, I pictured soft-bags, like throw overs.

That's what these are replacing.

 

[Rambunctious]

I know how to mount bags but in this instance the trim is a liability not an asset so let's get back to my original question and not try to over analyze it.
Will 1/8" thick aluminum plate be strong enough for what I want to do?

1/8th" is pretty strong so yeah I think so... how much weight are you going to carry?...

 

[Ringel05]

1/8th" is pretty strong so yeah I think so... how much weight are you going to carry?...

I'm trying to not go with steel to keep the weight down.

 

[Rambunctious]

I'm trying to not go with steel to keep the weight down.

Got ya... aluminum should work just fine...

 

[Ringel05]

So everyone doesn't have to guess what it looks like here's some pictures. It's kinda hard to see but the bag mounting brackets only have a very small point of contact due to the trim.

 

[Rambunctious]

So everyone doesn't have to guess what it looks like here's some pictures. It's kinda hard to see but the bag mounting brackets only have a very small point of contact due to the trim.

View attachment 665007

View attachment 665008

I think you are going to want to flush that fit....

 

[Ringel05]

I think you are going to want to flush that fit....

That's why I want the flat plate. Using the spacers between the fender and the plate will square the plate. The bolts will run through the inside of the bag, through the bracket, through the plate and through the spacers.
Here are what the spacers look like:

The fender has an inset specifically for the spacers to square up anything that's attached too it.
Here you can see the side inlet mounting holes.

 

[mudwhistle]

So everyone doesn't have to guess what it looks like here's some pictures. It's kinda hard to see but the bag mounting brackets only have a very small point of contact due to the trim.

View attachment 665007

View attachment 665008

Some license plate frames are made of aluminum.
Aluminum alloy can be pretty strong stuff.
Touring bikes are made of the stuff.

 

[Rambunctious]

That's why I want the flat plate. Using the spacers between the fender and the plate will square the plate. The bolts will run through the inside of the bag, through the bracket, through the plate and through the spacers.
Here are what the spacers look like:

The fender has an inset specifically for the spacers to square up anything that's attached too it.
Here you can see the side inlet mounting holes.

Oh I see.... use those spacers for sure maybe lock tight the bolts...
but I'm no expert....
I just ride em... I don't know what makes them work...

 

[fncceo]

If it were my build, I would put a plate behind the fender as well

plate ---- fender --- standoff --- plate

with an appropriate sized carriage bolt through the standoffs.

In this way, the holes in the fender aren't taking the entire strain.