Let the V20 build begin

[BentAero]

Yes, boxing in the ID of the

Yes, boxing in the ID of the tube is certainly an option, but I think it would be easier to just weld in the piece we cut out, essentially putting it back to original condition. One of the nice things about aluminum is that after welding, it will slowly harden over time, therefore it doesn't 'need' to be heat treated. If it were something severely stressed such as suspension linkage, heat treating would be far more important.

In my defense, I must confess that I am, and have been since Dec 19, under the influence of post-surgical mind-altering drugs. That's my story and I'm stickin' to it.

 

[Andrew 1973]

I didn't know that aluminum

I didn't know that aluminum will harden over time on it's own. Very interesting!

 

[LarryOz]

I think a thick enough "disk"

I think a thick enough "disk" that Gary and I had discussed will probably do the trick and allow the clamp to tighten onto the boom well enough.
Of course if "someone" would just say: "Hey Larry - I have a V2.x slider you can have" - then my problem will be solved, as I would really rather have the old style boom and slider anyway. (might just have one made in the end if nothing turns up)
We'll see how it goes. In the end, I could also swap booms from my V2.0 and V20, and assign the V20 boom to the KICKR for life, and ride the other one the road and race with it.
Stay tuned to this channel for more!

 

[BentAero]

The fix was actually pretty

The fix was actually pretty simple; cut a small ring from the leftover stub of male-slider boom and slide it inside the female portion from the open end. It fits just snug enough to stay in place.

Once the insert was in place, Larry cut off a tiny piece of the "cutout" chunk of the female boom and attached it to the insert. Now the clamp has the same surface to bite against as it originally did.
It's a poor photo, but you can just barely make out the step between the two pieces of aluminum.

The end result is that the fork stem will now fit up inside the boom like the earlier V's do allowing some fore and aft adjustment, as well as height adjustment without cutting off the fork stem. There is also room to install/remove the Di2 charging block.

 

[LarryOz]

Thanks Gary for posting those

Thanks Gary for posting those pics of the boom "modification".
It works great like this - clamp is nice and tight, so feel pretty good about the mod.
Following are pics showing the installed XD-15 BB, cranks, pedals, Rotor XQL rings, front and rear derailleurs.
Next up; brakes and stock seat/headers install.
Still waiting for longer di2 wires to finish the installation and tuning of that system, plus brifters and of course handlebar.

 

[Rick Youngblood]

Looking good Larry!
What's

Looking good Larry!

What's the story about the double holed crank arms? Did Mark do those as a custom build?

 

[LarryOz]

Oh - yeah - double pedal holes

Forgot to mention that. I did them at my work (with help)
We build grinding machines there. I am the programmer and the IT guy.
Anyway, I have 150mm cranks on my current V2.0, but wanted to experiment with something a little shorter, so just marked and tapped new holes at 140mm mark
I am also working on a couple of really cool adapter plates that will have crank holes from 85mm to 150mm in 5mm increments.
They will attach to the crank arms on both sides and will allow me to quickly change the crank lengths and run virtually simultaneous tests on different lengths. My Vectors pedals will also fit into the adapters so I will be able to record full power readings with them.
I have been pretty successful in training myself to pedal at 100 rpm on the KICKR, so now 90rpm feels "slow". I can easily accelerate to 135rpm pretty easily, which really helps my power curve. I think even faster rpm's will also be possible with shorter cranks lengths with no loss of power.
I am also very anxious to try out the new XQL rings and do some testing between the regular Rotors Q-rings and the XQL.
More later.

 

[mzweili]

boom cut out

Larry and Gary,
excuse for my skepticism.
The rather small wall thickness of the boom and the huge cut out with the stress raisers caused by the relatively sharp edges......
Sorry, but I wouldn't go on the road with this.

 

[mzweili]

Larry,
It's not that I'm

Larry,
It's not that I'm looking to kill your fun with the new V20.
Just I wouldn't like to read something similar from your side as I read from Bob Pankratz in his ?''Broken but not Beaten''.

 

[BentAero]

Marc,The boom may appear to

Marc,

The boom may appear to be weak, but it doesn't seem to be effected by the hole at all.
In the big picture of 'what could fail', this isn't even on my radar screen of risk. A crash from hitting a pot hole and blowing a tire on a high-speed downhill is a much more likely scenario than the boom collapsing.

Everyone has a different level of risk/comfort. Some jump out of perfectly good airplanes, some play golf during a lightning storm. Others ride bicycles with modified parts.

 

[mzweili]

Everyone has a different level of risk

Agree.
I learned to be very careful.
My professional background is mechanical engineering in aerospace and public mass transportation (subway and commuter trains).

 

[Eric Winn]

The problem is the collapse

The problem is the collapse is most likely when this happens:

A crash from hitting a pot hole and blowing a tire on a high-speed downhill is a much more likely scenario than the boom collapsing.

Un-modified, the structure is extremely strong and, in my experience, does an exceptional job protecting the rider during a crash. I'm leery that this modification will result in the boom folding or breaking at that cutout in a crash - perhaps even a relatively mild one.



-Eric

 

[Wannabe]

Larry My Brother...

I would like to add my thoughts.

First, what does the inventor of the bike think about the cut in the boom? I would be inclined to follow his advise.

Here is my take on the issue:
Observing the hole via a picture may leave some wiggle room, but IMHO, it might cause problems. I say this from the following experiences: Life time of building, motorcycles & racing them, airplanes & flying them , lots of boats and cars. Professional Auto mechanic, Degreed electronics tech.... so on and so forth. That is not important..... the following is......

I get the feeling you have some gut level reservations? Listen to your inner voice!

also, there is a "lever moment at play here" Some serious mechanical engineering required. And then.... that is still a best case/ some-what of a guess. Error on the side of caution.

YMMV , FWIW etc etc etc....

 

[hamishbarker]

Leaving aside the concerns

Leaving aside the concerns about clamping, which the fix with a bit of tube inserted will probably allay, there is the question of torsional stiffness of the now-open section of boom.

Torsional stiffness of a closed tube such as the unmodified V20 boom is orders of magnitude greater than the now open sections. John T probably knew this when the V20 boom was changed to a closed tube from the V2.0 (very expensive to manufacture) machined, cut and welded cage boom. The greater stiffness of a closed tube would mean a thinner tube wall thickness could be used and still be stiffer than the old boom, saving weight. Or with the same wall thickness, a smaller boom diameter could be used with the same stiffness but reduced weight and reduced frontal area (aero benefit, however tiny).

The hole isn't the full length of the boom, so maybe it's only going to have a minor effect on the boom stiffness, but given that one of the advantages of the cruzbike Vendetta is supposed to be that the stiff boom allows efficient power transfer with minimum frame flexing, any loss of boom torsional or bending stiffness does seem to squander that advantage.

 

[richa]

My 2 cents


I think the risk here is in simply riding a bicycle on the roads in the US. I'd put the increased risk from this modification at negligible. Although I would personally file the edge smooth to lower the probability of some type of fatigue crack forming over time.

I'm more curious over the benefits of the V20 over the 2.0. Clearly the 2.0 is more adjustable out of the box. I find it somewhat bizarre that the silvio now offers the ability to get the boom more horizontal then the V20. I can see it's cheaper to manufacture with common components between the bikes, but the price didn't go down. And cost-savings isn't usually something companies are primarily concerned about with their top of the line products. Also, Cruzbike already had a bike at this price point. So I still can't figure out this move.

And while all the Vendetta's look awesome, the 2.0 I think is the most awesome of all. IMO, the most bad-ass looking bike ever manufactured.

I'd be be very interested in hearing your first-hand comparisons on riding them.

Thanks in advance,

Rich

 

[iow]

imho, cutting a hole in a

imho, cutting a hole in a stressed and safety critical component is asking for trouble - as with most things, it will be fine until it fails...

 

[Zzorse]

And while all the Vendetta's

And while all the Vendetta's look awesome, the 2.0 I think is the most awesome of all. IMO, the most bad-ass looking bike ever manufactured.

Agreed.

 

[Robert Holler]

Many here have hit the points

Many here have hit the points that need to be made, but definitely this is a mod that as a company we cannot support.

Looking at that second picture in post #63, you could have possibly used a single thinner spacer on top of the pivot clamp - and just inserted the star nut further, cut the steerer tube shorter, and had the boom clear it all as stock at the same height as your picture.

That said - the need for adjustability - from 2.0 to V20 this change was a major factor. Yes the unit does not sit as low as before, but actually I get more requests for people needing to raise the handlebars than the other way around.

The old slider style was also susceptible to rounding out the holes at the pivot clamp under stress of riding and having a gaping hole there was both expensive to manufacture and prone to manufacturing errors and a risk for failure in the aluminum. I can tweak mine back and forth on my personal bike if I twist hard enough. Not a part that would be good to have fail at any speed.

But the biggie was adjustability for the larger market - the V was a difficult bike to fit people if the reach was not "just right" since the fore and aft adjustability was rather limited. The current design represents the best of aero, flexibility of fit, manufacture, and strength - which was important if we want to turn Cruzbike into a serious bike for a bigger market where people want: fit, adjust easily if needed, and ride fast.

Other factors like whether it looks cool or not/what is more aero or not are all 6 of one and half dozen of another (my personal opinion) for many potential Cruzbikers. For all the comments on how cool the old style looked I encounter people who thought it looked "too heavy" or "fat" and they actually prefer the new style. So...

I would cut that fork steer tube as short as you can to get the bars as low as you want, and work with someone who can do an insert or something to fill that hole - like doing a scab on a floor joist - maybe welding it in there if possible. A quick sit on the bike with some good serious torsional forces applied will reveal any flexing or twisting at that hole as you have it now.

Robert

 

[BentAero]

"See kids, this is what

"See kids, this is what happens when you mix vodka with oxy. Let this be a lesson to you."

Hypothetically speaking, if one were desirous of replacing said boom, would that opportunity be among the limited options available?

Seriously, can we buy a replacement female/handlebar section of v20 boom, or better yet, the male/handlebar section of v2.0 boom w/clamp? (He has the female section)

Please tell me CB has spare parts available... they do, right???

 

[ak-tux]

That Cutout on the Boom/Slider is scary to me

I am not an expert but my first impression of picture in post #63 is: " Oh my goodness! What has he done to his bike! That cutout on the Boom/Slider is scary! "

That is a high stress point on a Moving Bottom Bracket (MBB) FWD bicycle. It is the last place that you want a weakness in the structure. To give you a an idea of how much force is generated on the boom and handlebar when climbing, take a look at the picture below of a failed handlebar on my homemade MBB bicycle a couple of years ago. Luckily for me, I was going uphill and the failure, though sudden, was not catastrophic. I replaced the handlebar with a stronger, heavier one, that is thicker near the stem clamp area.

The forces generated when pulling and pushing uphill are strong, cyclic and repetitive. Any weakness in the material will eventually be exposed. IMHO an expensive, factory made bicycle like the V20 should be able to work well with minimal tweaks. Cutting a steerer tube is industry standard practice and would have been the better option. Extending a threadless AL steerer tube is also possible with a standard extender.