CB350 bracing

No I'm digging up the old CharlieY vs. The Whole Northern Hemisphere debate, don't worry. I'm building up a fresh frame for 2009 and was asking my father (who was a structural engineer for British Aerospace) about the typical bracing from the backbone to the frame tubes that run up toward the shock mounts. He's not a bike rider (sold his soul to Mini Coppers back in the 60s) but sees no real advantage to bracing there. Comments?
Also the new frame is a SL350K0 frame, it is very similar to the CB/CL chassis but with the addition of a lower tube under the engine cradle and a 20mm longer swingarm. Oh, and a welded in steel inner rear fender!

 

Dean-I agree with your dad, not sure the traditional tube from backbone to sides does much: unless you triangulate it across the back also...but then you can run into tyre clearance if you don't curve it....the 20mm longer swingarm sounds like the ticket to improve weight distribution...didn't know THAT...[thanks] rumor has it that swingarm flex is the weak link in the system...

 

CB's and Sl's are different but....the bracing we did on Steve's bike (a CB) was a bar between the shock mounts, and two bars from the rear motor mount area to the frame tubes to the shock mounts. We did the second item mid-season and his seat of the leathers impression was that it made a noticeable improvement.

I think we also welded the seams on that frame but can't be sure.

 

Lets see here.....who actually started that?....somebody saw a bike somewhere........and said they thought it was outside the rules...hmmm....wonder who that trouble-maker was...??...

I braced mine mid season, and noticed a difference.....I was running braced SA (bent my other, crach), no braced frame....doing the frame made a good diffenence

I went slightly higher than the motor mount, actually up above the second threaded hole. I agree with Charly P about spanning in front of the tire (triangulation), and actually have several pieces cut and fab'd.

I started a little higher than some I've seen, but with no upward angle....I ran horz to the ground, about half way up.

I used square tube on my mid-season job (its what I had).....round tube, 1/2", for the other couple I'm doing now.

I like that welded plate on that frame Dean, and I'm already thinking of who can shape something, and weight....as high as that thing comes up it probably helps the shocks too.....there is also an extra brace on bottom too, right?.....Early SL, non-dual downtube....

Also spanned shock mounts.

I also plan on boxing in the upper horz's under the seat / battery area.

 

I saw this post and thought "well it must be winter time on the WERA board." I have an SL frame that was raced, not by me, and it is braced everywhere. I am not sure about the SL's but the CB's will crack the rear motor mount if it is not braced. I took it upon myself to research this for everybody this year. Please no applause, just throw money. Anybody need some CB 350 engine cases? Only raced one season. Cheap. Automatic chain/reartire oil system, no charge.

 

Hey Steve...is your SL the dual downtube?....I've got 2 of those, and been thinking.

The one Dean is talking about is an early SL....similar to the CB / CL frame, but with extra stuff....welded plate inner fender.

 

Charlie, yep, dual downtube. When I had it sand blasted, looks like someone made the whole rear of the frame custom. Lots of nice brasing (sp) work.

Just exactly what are you thinking........?

 

right now I'm thinking I wanna see some pics of your frame.......I sandblasted one of mine a few weeks ago....I did one SL dual downtube, and one CB / CL....I'm gonna pick one and build it.

Hey man, looks like I'll be making a trip up to see Wayne and Mike Wells this coming saturday....how far are you and chuck from him?

 

'bout 2 hours. Prolly out of your way if you are going up I-75. We live in Bowling Green, southern part of the state. I have to run up there next weekend too. Got to drop off a head for Bill and take Waynes pop-up back to him.

 

right now the plan is to be at mikes around lunch sat....if timing works out I'll buy ya a beer.

Hey, is lexington EST?

 

Cool, yep Lexington is EST.

 

this frame won a few races. although not with me on it. it was the best handling cb ive ever ridden.

 

Somebody say party at Mike Wells Racing?
Poke around in his shop, bench race, and keep him from getting any useful work done?

I'm in!


(unless I go indoor dirt track racing)

 

would this be too much "bracing" for a stocker?

its an sl frame.

 

Can you do too much bracing? That is very cool. Nice job.

 

Hey Joe....that SL is sweet, I've been pondering the seat area.....thanx.

Does the bar from the neck (other bike) to the SA bolt on at least one side? how do ya get the motor out?.....does it clear then drop out?

Hey Chuck, I cant speak for Mike, I was invited by Wayne Hope to be there between 12 and 1.

Any minute now I'm expecting Mike to chime in,...like....Huh?

 

Hey y'all come on. Watch out though, I might put you work.

Mike Wells
AHRMA & WERA #341

 

Steve-you cracked a CB350 frame at a lower/rear engine mount? I had heard of the lighter SL frames breaking there....

 

joec--nice, but weld the backbone tube back in there would ya?

 

Steve cracked the motor cases, Charly.....