back from the IBR

[ponyfool]

I have a Givi 46L bag on there right now with that special aftermarket mounting plate...i imagine with the weight of that plate leaves little weight you can use in the Givi bag.

Which "that" are you talking about? The Givi mount, the OHFJR mount?

 

[Nikk]

So, is there a theory that the Givi mounting rack would provide more support than the Premier Cycle Accessories OHFJR rack?

I've been wanting to pull the trigger on a trunk, but now I'm scared! Yup, I said it I'm scared

-Nikk

 

[wpbfjr]

just throwing mt hat in the ring to say i had the same pelican/frame failure on my way to eom...

thanks for the write up, iggy...

gerauld, can i send my rack back for you to add-on supports that anchor to the factory points under the pillon seat?

dana

 

[vectervp1]

Something I though of when this thread first came out but forgot to post...

I've seen a few of the bikes that have reported failures and all of them had one interesting thing in common. All of them didn't have a grab rail on them. This makes me wonder if the way the stock grab rail/rear rack (and the Givi grab rail/rear rack) helps support the weight of items back there. Sort of triangulating that structure, and helping the subframe from flexing as much.

I know that on Iggi's, IronMaiden, Big Chief SP, and Go Far's bikes, they completely removed the grab rail and connected their top cases directly to the three mounting bolts on the rear of the bike. Could it be that if you were to somehow create mounting plate that also tied back the mounting point for the rear grab rail you wouldn't have this problem?

 

[rickcorwn]

Well I didn't tie my mounting plate to anything special but I left my stock grab rail in place.

We'll see <shrug>

 

[ponyfool]

So, is there a theory that the Givi mounting rack would provide more support than the Premier Cycle Accessories OHFJR rack?
I've been wanting to pull the trigger on a trunk, but now I'm scared! Yup, I said it I'm scared

-Nikk

The Givi rack mounts in 5 places, the 3 bolts on the tail, and 2 under the pillion seat.

The OHFJR rack only mounts to the 3 bolts on the tail.

So, just based on that you'd think maybe the Givi was more stable. However, that doesn't really answer the question though, because even with the Givi rack, ALL of the weight is on those 3 bolts. The only thing I personally think the Givi offers is less bounce, thus possibly more stability.

 

[BrunDog]

Remember: Weight down is different if it is supported by the grab bars. The grab bars will prevent the load from torquing the three bolts. It is the torque (moment) and shear force downward that I bet are combining to break off the tail section.

In any even... 7 pounds. WTF is that? I can fart 7 pounds. This was not a good place to try to sae on weight...

-BD

 

[Joe2Lmaker]

I've seen a few of the bikes that have reported failures and all of them had one interesting thing in common. All of them didn't have a grab rail on them.

Remember: Weight down is different if it is supported by the grab bars. The grab bars will prevent the load from torquing the three bolts. It is the torque (moment) and shear force downward that I bet are combining to break off the tail section.

vectervp1, I've been watching this topic hoping the engineers chime in, but I wonder if there is not enough traffic in the Long Distance discussion. Maybe you should ask it in Technical Discussions.

BrunDog, I thought that too, but now I don't think so. Extending the mounting system to include the grab rail anchors doesn't make it that much stronger does it? The pivot point or fulcrum doesn't move, but now there is an additional anchor (load) in front of the pivot point. So, the load where the subframes are cracking (pivot point) doubles right?

 

[Go Far]

The repair

I thought I'd give it a test

Subframe came out with flying colors.

Got a flat, tho :blink: :glare:

 

[wfooshee]

BrunDog, I thought that too, but now I don't think so. Extending the mounting system to include the grab rail anchors doesn't make it that much stronger does it? The pivot point or fulcrum doesn't move, but now there is an additional anchor (load) in front of the pivot point. So, the load where the subframes are cracking (pivot point) doubles right?

I think it isn't the load that's causing the failure, but the flex. Removing the grab rails allows more flex. The rails brace against movement at the rear of the subframe, like a gussett. Notice that ALL of the weight loaded on the rear is BEHIND those three bolts. The grab rails are under tension when the rear is loaded. Think of the weight as hanging from the rails, not actually being supported by the rails.

I don't call it a design flaw, I call it a failure of an improperly modified component. Those rails are part of the structure.

 

[Joe2Lmaker]

Removing the grab rails allows more flex. The rails brace against movement at the rear of the subframe, like a gussett.

It's clear to me now.

Go Far's photo shows how the grab rail strengthens the rear rack mount.

The subframe extends back, then rises above the tail lights. Those are the first two sides of the triangle. The area of the subframe suporting the rack would be much weaker without the third side of the triangle, provided by either the stock grab rail or aftermarket brace.

 

[Ignacio]

Removing the grab rails allows more flex. The rails brace against movement at the rear of the subframe, like a gussett.

It's clear to me now.

Go Far's photo shows how the grab rail strengthens the rear rack mount.

The subframe extends back, then rises above the tail lights. Those are the first two sides of the triangle. The area of the subframe suporting the rack would be much weaker without the third side of the triangle, provided by either the stock grab rail or aftermarket brace.

I came to the same conclusion in April by first trying a mount that removed the rack and tried to use the 3 mounting points. After I had my cracked frame welded I decided that drilling holes in that nice pristine stock rack and getting 5 points of support was less of a shame than a rear case falling off. It's that moment that you decide to drill holes in your painted rack that gives one pause. :blink:

Since then...it's run like a champ...perhaps even over-engineered. It's very possible though that with a welding job alone that the 3 point will still work.

This Jungo Road looks like cake and a great shortcut to Gerlach.

 

[Go Far]

So I'm planning a ride down to Austin, Tx next month. I was giving the bike the once over and discovered this:

Right side

Left side

It's time to rethink the setup <_< :banghead:

5-point trunk mount -here we come

 

[Bounce]

I thought I'd give it a test

EEEK!

[thud]

https://www.fjr-tips.org/rides/jungo.txt (for those who don't know the reference).

 

[Go Far]

I thought I'd give it a test

EEEK!

[thud]

https://www.fjr-tips.org/rides/jungo.txt (for those who don't know the reference).

The nice grass in the pic sure makes it look like cake- maybe with a few school crossings to slow down for :help: :rip_1:

 

[Bounce]

Yeah. I would suspect that the photo was taken somewhere in the area described in the first paragraph. I can't say as it was already dark when I passed that way.

 

[Brodie]

Damn,

I just google mapped Jungo road from Winnemucca to Gerlach.

100 miles doesn't sound like much, but 6 hours? WOW


Definitely not your typical street bike trip.

Put about 40 lbs. in the trunk and it would be a great test for the rear sub frame.

Brodie