Frame strengthing gussets

[1965Cobra427]

I am aware of at least 2 structural frame failures of Brammo cars. Mine and another car. Both had TONS of track time on slicks. Both had one or more upright/bearing failures. These cars definitely have had far more abuse than most Atoms out there, BUT the frames DID fail in the welds. Both cases had a similar failure mode. The forward lower transverse tube of the engine cradle (the tube to which the front engine mount is attached) failed the welds at both ends where the tube intersects the two bottom longitudinal tubes of the engine cradle.

My car failed first. I never brought that to the attention of the Forum believing that it was an anomaly. In the case of that car, the tube in question had been replaced at the factory using MIG welding after the original tube was removed. That followed my previously reported and discussed "barb-wire fence" incident in which that particular tube was bent. The failure of a "repaired" frame tube seemed irrelevant to other Atom owners and so I never reported it here.

The second failure occurred late last season to another car which did not have a "repaired" cross tube, but which has been run very hard over a long period of time.

Both of the cars in question have had their chassis' repaired and additional gusseting added. Since the engine is currently removed from my other car, I am having Tom Smurzinsky fabricate and install gusseting to it as well.

Since both of the cars I know of which experienced the failures have had very extreme track lives, I do not necessarily believe that this will be a problem for other Atom owners.

With respect to the welding process that has been described in this thread, it should be noted that in later production of the Brammo cars this procedure is reported to have been discontinued in favor of quicker and less expensive MIG welding process.

[Radowick]

[quote="1965Cobra427"]
I am aware of at least 2 structural frame failures of Brammo cars.
[/quote]
Thanks 1965Cobra427 (sorry about your car though).

[quote="1965Cobra427"]
...............BUT the frames DID fail in the welds. Both cases had a similar failure mode. The forward lower transverse tube of the engine cradle (the tube to which the front engine mount is attached) failed the welds at both ends where the tube intersects the two bottom longitudinal tubes of the engine cradle.  
[/quote]
Thanks 1965Cobra427.

[quote="1965Cobra427"]
............... I am having Tom Smurzinsky fabricate and install gusseting to it as well.
[/quote]

Thank You 1965Cobra427!

[Radowick]

[quote="1965Cobra427"]
With respect to the welding process that has been described in this thread, it should be noted that in later production of the Brammo cars this procedure is reported to have been discontinued in favor of quicker and less expensive MIG welding process.
[/quote]
Whether welded it using TIG (electrode - with the filler rod feed by hand), or MIG (a thin filler wire is feed to the weld thru the tip of the welding "gun" by the pull of a trigger), the strength of the weld will be the same, provided equal skill is used. It is the type of filler rod/wire material used that will determine the weld strength, not the method of doing it. MIG is quicker for sure. 

[Gage]

This is one of the best threads on the forum.   

[1965Cobra427]

Once I get photos of the gussets on my car, I'll post them for what it may be worth to other Atom owners.

[NormLarson]

Here are some screen shots of Spanky's Catia model that he asked me to post.

[img width=748 height=600]http://www.imgtree.net/files/6m9w86l9o9t7yyxtfexg.jpg[/img]
[img width=776 height=600]http://www.imgtree.net/files/3l3nqlgnkbpbyf2otewq.jpg[/img]
[img width=697 height=600]http://www.imgtree.net/files/bqu8mv78twgjr5guae8j.jpg[/img]

Nice drawing! 

[1965Cobra427]

Thanks for the excellent illustrations of the chassis Spanky - well done!

The failures I know about are evidenced by the fracturing of the weld joints where the blue tube is attached to the gray tubes at each end.
Without the benefit of actual finite element analysis, I have imagined that two forces introduce loads into these joints.

1) the up and down and rotational loads introduced at the engine mounting point.

2) the push-pull loads transmitted from the forward mounting points of the lower control arm pivots on braking and acceleration.

Since both cars in question have sustained at least one failure of the upright/bearing and have been running hard on slicks at a track where bumps frequently accompany tight corners, I tend to suspect that the lower control arms may be more of the problem. In addition to that, compare the heavy cross bracing of the chassis at the rear pivots of the LCA's with the lesser cross chassis bracing at the front. Of course the diminished cross structure is because the engine and transmission are in the way.

I could be way off base on this conclusion. On my car we are adding triangular gussets which will tie the blue and yellow tubes together. It will still not be nearly as strong as the rear with it's big x-brace, but should be an improvement.

[dingo]

Do you foresee any issue with dropping the gas tank out the bottom with those new members in place?

[NormLarson]

DP sells a brace for this area.  Looking at his website, it looks like all can still function ...

[dingo]

Hi Norm:  I have the Palatov brace installed. It is removable, whereas these gussets appear to me to be welded in place. Hence the question.

[NormLarson]

My only point is that it looks like they could be engineered so that it was possible.  I haven't spent the hours that Spanky obviously has, so, this is his to answer

[dingo]

On My frame (Brammo 2/3) the lower longtitudinal frame members do not extend (more than 1/4 inch or so) beyond the crossmember shown in blue or the front side members that hold suspension brackets.  So I'm not sure where this new member would be seated.  Perhaps it has to be fluted?  I'm pretty sure I've mucked up terms, by fluted, I mean cut at an angle to mate with the surface at the lower extremity and either side of blue member.  

[CalScot]

[quote="dingo"]
On My frame (Brammo 2/3) the lower longtitudinal frame members do not extend (more than 1/4 inch or so) beyond the crossmember shown in blue or the front side members that hold suspension brackets.  So I'm not sure where this new member would be seated.  Perhaps it has to be fluted?  I'm pretty sure I've mucked up terms, by fluted, I mean cut at an angle to mate with the surface at the lower extremity and either side of blue member.  
[/quote]
I am sure the gussets in question are basically small pieces of plate steel cut at 45* the the two tubes at the joint and not extra tubular members added.

If it were a new piece, the term would be cut at a tangent to the main member of the joint. Anytime you have more than two tubular members welded at the same joint it is called a node. Usually described as a K or Y "node" joint.

I might have to post pictures of my frame failures and the repairs because they are not anyhwere near the failure areas Randy has had. I still say if it aint cracking....don't mess with it!  

[Radowick]

[quote="dingo"]
On My frame (Brammo 2/3) the lower longtitudinal frame members do not extend (more than 1/4 inch or so) beyond the crossmember shown in blue or the front side members that hold suspension brackets.  So I'm not sure where this new member would be seated.  Perhaps it has to be fluted?  I'm pretty sure I've mucked up terms, by fluted, I mean cut at an angle to mate with the surface at the lower extremity and either side of blue member.  
[/quote]

 These images are of my car using measurements that are as close as I could get. I really think I got it very close. So why your "lower longtitudinal frame members do not extend (more than 1/4 inch or so) beyond the crossmember shown in blue" is something I can't explain. But these images are what my car does look like for sure.
 I agree, that before anything is added to anyone's frame, they should check to verify for any issue should there be a need to drop the tank out in the future.
 When I can get this model analyzed, I will be sure to post my results.  But first, I need to add to the model the members that pass under the seats. Those are the hardest to get measurements of.      

[DarthChicken]

[quote="Spanky"]

 These images are of my using measurements than from my car as close as I could measure it. I really think I got it very close. So why your "lower longtitudinal frame members do not extend (more than 1/4 inch or so) beyond the crossmember shown in blue" is something I can't explain. But these images are what my car does look like for sure.      
[/quote]

here is what mine looks like, it's basically a strait down shot on that joint.

[img width=450 height=600]http://i255.photobucket.com/albums/hh12 ... 47a255.jpg[/img]