Chassis rod torque

[Guest ratchethack]

As most of you Guys know, the lower "pork chop" nuts are threaded on a rod that runs though the rear transmission mounting bosses. I've been a little concerned about the optimum torque to put on this, as the rod just seems to stretch when I go more than 20 lbs. At this torque setting, putting the bike on my shop stand, which cradles the bike on these nuts, actually rotates the nuts and the rod whenever I raise and lower the bike. This "design feature" seems more than a little cheesy to me. I'm guessing this is a major source of the chassis slop that Guzzi attempted to address with additional gussets and triangulation in later-year models. Anybody know if the rod is high-tensile rod, and can it take more torque than this?

 

EDIT: Come to think of it, this brings up the original design concept for the spine frame. How hard and/or expensive would it have been for the engineers to take full advantage of the massively ridgid engine/trans unit, like they did at the front end, and have much shorter high-tensile bolts thread directly into the casting from each side, instead of just hanging the trans in the middle of a 14-inch long "loose goose" flexi-flyer rod???

[txrider]

Ratchet, I had some of the same concerns when I was working in that area of my bike. I do recall that disassembly was accompanied with a loud "whack" when I broke the torque on one of those nuts so I reassembled using 35 Ft lbs which seemed ok. I did shim the 0.040" air gap at the cross brace-r/h pork chop joint so there was minimal or no flex of the pork chop during re-torquing.

[Guest ratchethack]

Txrider, thanks for your reply. Now, however, I'm more concerned about your bike than I am mine.....

 

Per our previous correspondence re: your use of shims in the chassis, I most urgently suggest that you should have NO shims between any of the chassis components! When the chassis goes back together, careful taking up of torque on the nuts & bolts in the proper sequence will self-align the chassis with minimal stress on the components. What appear to be "gaps" will disappear as everything is drawn together - as is right and proper. Shimming up any "gaps" will throw things out of alignment and present more opportunity for sloppy joints and bolts that will have much more of a tendency to work their way loose!!! I humbly but firmly suggest that you take all chassis shims OUT! :luigi:

[txrider]

Ratchet, while I humbly defer to your greater experience and excellent judgement in all Guzzi matters I believe if you could see first hand the item we're discussing it would be apparent that the rear lower cross brace on my bike is slightly undersize at that junction. Those gaps were present after complete removal of the brace and then upon reassembly, carefully re-torquing of all fasteners in a criss cross manner which attach to the pork chop. In fact I tried loosening, retorquing twice to see if there was any change. The result was the same.

After assembly the rear wheel alignment was checked using your laser level technique and all was in order. Plus the bike tracks well moving down the road. So for now, at least, the bike checks out and I'm trying this setup. Thanks for the concern and I'll let you know if a problem develops with this approach ( they don't call me bullheaded for nothing).

[Guest ratchethack]

Looks like I'm hijacking my own thread here, but I can't resist.... Txrider, if it came apart without shims, how is it that it needs shims going back together?

[txrider]

Ratchet, as I said before you're much more qualified on Guzzis than I am and I feel I'm out of my depth getting into a debate with you about this. However, my reasoning is as follows- it appears the porkchops are located by the 3 bolt circular fittings on the spine cross pieces. That establishes the inside distance/location of the porkchops. And I'm making an assumption that that distance is correct. When the lower cross brace is installed it should come into contact with the porkchops at all three attachment points on l/h side and two on the r/h side. Otherwise the porkchops will have to flex(bend a bit) somewhat as the hardware is tightened. A few thousandths I can imagine but not 0.040" That's the part I have a problem with. I think the porkchops were not intended to flex/bend that degree during installation of the cross brace. Just doesn't seem reasonable from an engineering design perspective. So I measured the gaps, and machined and installed sst shims of the proper thickness to eliminate that flex.

As for the question about why shims would be required in assembly when they weren't there in disassembly- First, I can't honestly say if those gaps developed when I removed the cross brace because I wasn't looking for that. But they were there at assembly unless corrected. And as much respect as I have for the guys that designed and assembled the LeMans I know from having been there that manufacturing tolerances can be tricky, especially welded up assemblies like the crossbrace. And if we can accept that errors can be made in shift pawl machining, improper heat treat in gears/shift dogs, improper selection of valve/guide materials, etc. then it doesn't seem a stretch to accept that a crossbrace could be made undersize and need shimming for proper fit.

[Guest ratchethack]

Hey Txrider - Please stop referring to my high qualifications on Guzzi's as if I had any. I'm just another Guy with an opinion. There are many many many better qualified Guzzisti wrenches hanging around here than moi.

 

I'm just offering up what makes sense to me based on my experience and observations in the spirit of open Forum discussion, whereby better knowledge & intelligence is often flushed out & brought to bear. Hopefully some of us, including me, can learn something in the process. I'm not interested in sparring with you or arguing whatsoever. Hopefully, if I get too far out of whack, one of the very many who are infinitely more qualified than myself will kindly (or otherwise!) weigh in and set me straight - as has been known to happen!

 

In my most humble opinion, a .040" clearance where you've described it should be well within mfg. tolerance. Chassis stuff doesn't call for anything near the precision of engine or transmission tolerances, for example. I'd say there's at least an order of magnitude delta 'twixt the twain. I'd also say that putting such a tiny amount of "spring" tension into the chassis and/or pork chops on assembly as things get drawn together is both normal and entirely acceptable.

 

When I put my chassis back together after having the trans out, I recall that the clearances you've described weren't spot on. I may have noticed even double the clearance you found, but I can't remember, and I wouldn't have thought enough about it to even measure it. I just torqued everything down as evenly as possible, fitting everything "snug" first, so that any misalignment in one area wasn't apt to show up magnified as more misalignment in another area, then torqued to spec in a sequence that seemed logical.

 

Please don't misunderstand. I'm not saying that you did something horribly wrong by sticking a shim in there. It may not present any kind of a problem - ever. In fact, for all I know, it may even make something better, I just can't imagine what that would be.

 

On the other hand, I wouldn't want to see you create more problems for yourself (higher frequency of fastner looseness, less rigid chassis, less instead of more correct alignment, etc.) than you think you might be solving, my friend. As for me, I wouldn't have any shims anywhere in my chassis under a similar range of observed clearance - or under any other circumstances, for that matter. But admittedly - that's just me.

 

Howzabout comments from some of you Guys with lots more years (& miles) of spine frame experience?

 

Oh yeah - [sheepishly tries to get the train back on track] while y'er at it, how about commenting on the torque on the chassis flexi-rod topic that opened this thread?

[jrt]

You guys are so nice

Well, my open-onion is that you shouldn't use shims on the frame- if you have to, something's up with the frame. A full set of measurements is available in the manual if you feel so inclined as to measure it up.

As far as the reaction rod goes, it has been replaced in the Ghezzi-Brian models with a threaded rod, so I say go for it Ratchet!

But I'm afraid that a lot of the slop is...just there. There's a lot of transfer through gears and each one of them contributes. I'm glad I'm not the only one who's noticed this. There is quite a bit more slop in the V11 than in my older Guzzis.

[txrider]

No problem from this quarter on discussions like these, I may be inflexible at times but definitely on the look out for ways to improve the bike and my methods in working on it.

On a note of further explanation and then I'll shut up- This bike, previously owned, showed signs of having been tweeked and worked on by one a whole lot less particular than myself plus it had an annoying screech with clutch release that I wanted to fix. So my mind set when I began disassembly and maintenance was to make everything as perfect as my ocd-like self could make it. The less than close fit of the cross brace bugged the hell out of me and I deliberated at length, including discussing it with you, Ratchet about what to do ( realizing that you disagreed with shims at the time). So, nontheless, in the shims went. Not too happy with having to do that but it seemed better to do than to see main frame compenents give a bit during reassembly.

I appreciate the discussion and this handling of a little disagrement. Other forums I've frequented there would be fireworks and name calling. By the way, I never did fix that screeching clutch release. Love the bike anyway...

[Guest ratchethack]

Txrider, when I first read of the "gap" you found, it sounded to me like you shimmed the "flanges" on the large cylindrical crossspiece welded to the spine, rather than the smaller cross-brace. Or worse, like you may have shimmed up only PART of one flange. I'd still be pestering you unmercifully for that. Now I think I understand where the shim went. I reckon I'll stop pestering you now, 'cause that doesn't bother me nearly as much... Even though I'd never do it myself...

 

I think of the pork chops as great big overbuilt alu forgings (or castings, can't tell which), that are attempting to impart legendary Tonti-frame rigidity to the relatively fundamentally challenged (stiffness-wise) Egli-type spine frame. As Jason pointed out, I suspect the spine frames could not and will never approach the massive, vault-like torsional strength of the Tonti. What could be considered "stiff" when compared to the Rock of Gibraltar??

 

Just thinking out loud on my way back to my original (as yet not fully answered) question... I submit that the pork chops are NOT absolutely ridgid, and it's actually a good thing they're not. I'm no engineer and I don't have the terms, but I reckon that "brittle" side-plates wouldn't be ideal in this application. I suspect that when the frame is stressed, as it would be at full suspension compression deep in a hard corner and heeled over, and then it's subjected to sudden WOT, for example, that the minute inherent flex in the porkchops and the rest of the chassis will attenuate most of the worst of the shock loading, while doing a fairly good job of keeping the overall geometry reasonably close to what the designer(s) had in mind. In such circumstances, I'd expect all the major chassis components to flex a little, as if the whole contraption were acting a little bit like a very stiff spring. The fact that Guzzi added triangulation and additional bracing indicates that they found a way to improve on what had been discovered to be an achilles' heel area of the chassis with the higher-output new engines. I believe they refer to this as the "wind-up" of the frame as increasingly encountered with the sharper and higher torque curves of higher-output racing bikes.

 

Now, getting back to my original question. It seems to me that the "flexi-rod" at the bottom of the porkchops is particularly poorly suited to complement the rigidity that the engineers were after in this area of the chassis. Seems to me that things might be easily improved here with at minimum, a stronger rod with enough tensile strength to get more than 20 lbs. of torque on it without stretching. Possibly, things could be even further improved by more careful fitting and tighter tolerances everywhere the rod passes through. I'm thinking that a slightly larger-diameter hardened rod with the ability to achieve maybe 35-40 lbs., as you found, Txrider, would be a great improvement. As is, I can't seem to get there without fear of snapping off the stock flexi-rod.

 

So Jason, a couple more questions. Are you saying that the GB bikes went to a stronger-than-Guzzi-issue rod? Aren't the GB bikes 5-speed trans only? Because of this, is there a difference in the rods between the GB and the V11? Do you know if such a stronger rod is available, and if so, where? I s'pose I could have one made up easily enough. Enquiring minds just gotta know, and I'll bet somebody's been down this road before.

 

Thanks in advance!

[jrt]

 

So Jason, a couple more questions.  Are you saying that the GB bikes went to a stronger-than-Guzzi-issue rod?  Aren't the GB bikes 5-speed trans only?  Because of this, is there a difference in the rods between the GB and the V11?  Do you know if such a stronger rod is available, and if so, where?  I s'pose I could have one made up easily enough.  Enquiring minds just gotta know, and I'll bet somebody's been down this road before.

 

Thanks in advance!

54514[/snapback]

 

 

Yes, and yes, and I don't know where to get one, but I bet McMaster-Carr (a materials/metal company) has your hookup. It would just be two heim joints and a threaded rod type deal.

Paul has a picture in the hollow axle thread that shows a different rod:

http://www.v11lemans.com/forums/index.php?...indpost&p=15185

 

And Zebulon also fitted one on his Daytona (keep a lookout for her) I added some cheesy red arrows to indicate what I was talking about.

I can't get the Ghezzi-Brian site to work for me- all the images come up '404'.

J

[Guest ratchethack]

Wow, thanks for the effort, Jason. But time out, my friend. I'm not referring to the brake stay, but to the transverse threaded rod that connects the pork chops at the bottom, the one that runs thru the rear transmission mount bosses. Where the shop stand lifts the bike.

 

If you re-read my admittedly torturously long diatribes with this in mind, I'm hoping it'll make better sense.

 

Thanks anyway.

[jrt]

Oh, my bad. I just skimmed ya'lls posts and and mis-read it.

Frankly, if you're fighting frame-flex on a spiney, it's a loosing battle. I do, however, recall a Japanese sight that had some aftermarket frame stiffening bits. Try this:

http://www.guzzisport.com/html/v11taisaku.html

I don't read kanji, though, so I can't help you much. They have some really trick bits for the various models.

[Guest ratchethack]

Oh, my bad.  I just skimmed ya'lls posts and and mis-read it.

54539[/snapback]

Thanks, Jason. No prob - I realize almost no one but maybe myself and Dave actually read posts that're longer than a paragraph. Huh, Dave?

 

BTW - I don't read kanji either but I know about that site. Far as I can tell, they don't do anything with the rod in question.

[Mike Stewart]

Rachet,

 

This stud had some torque on it when I removed it from my V11 Sport. It has a 12mm diameter and should be able to be torque to at least 36 or so foot lbs (most likely more).

 

Mine too made a snap noise when the nut broke loose. Are you threads free of oil when it is torqued?

 

Mike