"energy-sucking handlebar-on-a-stick" ???

[billyk]

"if you want to increase a Quest's performance, stiffening the energy-sucking handlebar-on-a-stick arrangement is where the biggest benefit lies" (Rich in the tea-leaves-II thread on 5/4/14)

I've seen several comments in these forums like the one quoted above, suggesting that some fraction of the work done by pulling alternately on the Quest handlebars loses energy by bending/twisting the steering column.

Since I put a fairing on my Q2, that has become very obvious. (See my post with photos "New homemade fairing for Quest" from 5 Jan 2014 http://cruzbike.com/new-homemade-fairing-quest). The fairing is firmly attached at 3 points: to the handlebars near the grips, and by a rod extending out along the top tube between the pedals (see photos). It also has a flexible vertical rod for adjusting the height above the bottom bracket (orange in the photos). When climbing or accelerating hard, that vertical rod bends back and forth quite a bit (say at least an inch either way at the top), representing relative movement between the handlebar grips and the BB. But those should be a rigid single unit, and any motion between them means effort is going into bending or twisting metal.

But where is the weak point allowing this? And more importantly, what can be done about it? Obviously this occurs at the worst time: when you're climbing and trying to direct maximum effort to the wheels. Is it actually bending the handlebars, or is it twisting the steering column, or bending the top tube? Is there an alternate handlebar arrangement that would reduce the bending/twisting?

 

[Charles.Plager]

I agree it's not ideal. I

I agree it's not ideal. I don't think there's much that can easily be done on these bikes (Quest, Sofrider, conversions). On the Silvio and Vendetta, the lever arm is much smaller, so the problem is greatly reduced.

I guess it's possible to replace the large stem riser with something beefier...

 

[chrisblessing]

Agree with Charles...

It's a lot of metal in the steering mechanism. I also have some big (RANS) bars, and find it disturbing only when climbing, but I've also learned that when climbing hard to grab the handlebar close to the stem, which makes a significant difference. Flex diminishes and I'm able to pull myself further forward.

 

[Rampa]

Flat bars

Flat bars (MTB style) might make a difference. The flex may be more in the Q's bars then the steerer of the fork.

 

[Rampa]

Is the steerer 1 or 2 parts on the Q?

I had originally assumed that the fork simply had a two foot steerer. Is this the case? Or is there a rise extender attached to top of the steerer?

 

[Jeremy S]

If the steerer tube is

If the steerer tube is actually twisting or bending, might lowering the handlebars on the steerer tube (which probably requires flipping around the stem toward you) help? This is how I used to ride my Sofrider since I didn't like having my hands so high.

 

[hurri47]

My conventional conversion,

My conventional conversion, with wide bars mounted directly over my knees, was not only very flexy, but I could not get the quill to stay put not matter how much I tightened the bolt. It was a two-fold disaster when applying hard effort.

MTB flat bars mounted MUCH lower and aft of the headset - behind my knees - increased the steering stiffness dramatically. The only downside is I have to ride with bent arms, which induces more fatigue compared to the old straight-arm position. (Conversely, I am forced to learn to rely less on pulling the bars except when maximum effort is required.)

For all the talk of the efficiency of the Cruzbike design, I think the fact that pretty much everybody has issues with bar location points to a basic design problem that is only resolved by going to Silvio/Vendetta layouts.

-Dan

 

[Jeremy S]

Dan, I didn't mind riding

Dan, I didn't mind riding with bent arms. But yeah, to straighten out your arms you could go to drop bars (or bullhorns), and eventually you will end up with something like Steve's turbo Quest.

 

[billyk]

Make Q steering more like Silvio?

Dan's comment above: "a basic design problem that is only resolved by going to Silvio/Vendetta layouts" gave me an idea:

Suppose the 2 functions of the pivot clamp at the top of the fork steerer tube were separated:

1. clamping down the conical bearings at top and bottom of the Diatech headset, and
2. providing leverage to turn the steering column.

This could be done by using a free-standing, separate clamp for the headset, and then extending the top tube until it could be clamped high up on the steering column, just below the handlebars.

This would make the steering action more like the Silvio/Vendetta, and remove any issue of twisting the steering column. It would not change the problem of bending the handlebars, and might worsen the problem of bending the top tube.

So again I ask: Where is the flex coming from?

Answering that question is prerequisite to figuring out a solution.

BK

 

[jphipps]

flex in steering

I would vote for the Diatech headset, I had problems with applying the proper amount of pre-load to the bearings and had to invent a jig that would at least allow me to pre-load, but no one seems to know how much pre-load is needed to stop any slop that would allow movement in the fore/aft direction. How did you pre-load the Diatech headset and to what level?

jphipps

 

[billyk]

Don't think the the headset can allow frame flex

I've had similar problems with getting the right tension on the Diatech headset, but I don't see how that could contribute to the frame flex. Even if the headset itself allowed free rotation, the clamp at its top would still be firmly attached to the top tube and the front end.

I'm really inclined to think it's the handlebars. Cruzbikes riders put much more stress on the bars than they would on a DF bike, so my guess is that stock bars - as used on the Quest - aren't built to take that, and they flex. When I get the time, I'll pick up a set of tough mountain bars and give that a try. ... But when do I have the time????

BK

 

[Shahmatt]

The donor bike used for my

The donor bike used for my conversion had Brompton M type bars with a stiffener installed. Perhaps you can use this method. Something like this:

http://www.jojbuy.com/taobao-agent-product-Motorcycle-stiffeners-hlebar-strengthen-the-blue_588793.htm

 

[billyk]

Diatech headset adjustment

Re jphipps question on adjusting the Diatech headset, pasted from Doug Burton's comment in the Quest thread "Is the Quest 2 front shock adjustable" on Sun, 2012-05-06 07:37 (http://cruzbike.com/quest-2-front-shock-adjustable)

http://sheldonbrown.com/headsets.html

"Diatech" headsets from Dia Compe use a special pair of collars, usually mounted just below the stem and above the top race. The lower collar has a beveled, conical top surface, which fits inside of a matching bevel on the inner circumference of the upper collar.

The upper collar has a gap at one point, with a binder bolt to squeeze the gap together. (This upper collar may also include a cable stop for the front brake, if the bicycle has a rigid fork and conventional cantilever or centerpull brakes.)

The handlebar stem is clamped tightly to the steerer, preventing the upper collar from moving upward. As the upper collar is compressed by the binder bolt, it squeezes the lower collar downward, taking up any slack in the headset bearings."

We used this headset for 2 reasons:

To allow headset tension adjustment without a 12" long stem cap bolt
To retain the headset to the fork when the bike is disassembled for packing.

So the key is to set the steering column as far down the fork steerer as you can get it, with the headset binder bolt fully loose, tighten the steering column bottom clamp, and then tighten the binder bolt to take up the slack in the headset. Once its operation is understood, it works a treat.

Cheers,

Doug

 

[Shahmatt]

I've just been looking at


I've just been looking at your fairing again. Nice fairing btw. I may have a go one day at fixing up one of these.

Just a thought. The bar ends that you have used to fix the fairing may make good connection points on which to install a stiffener. Provided that they are in turn fixed firmly on to the handlebar. A stiffener connecting directly to the handlebar (like with the Brompton M) would provide the best method though since there are fewer connections.

 

[Charles.Plager]

I don't think a stiffener

I don't think a stiffener would work in this case because I think it's the Cruzbike steerer extender that's twisting.

Replacing this piece with something heaftier may be your best bet.

 

[billyk]

Really? The steerer extender? Why?

Hi Charles -

Why do you think it is the extender? That is much beefier than the handlebar, and doesn't have much moment arm. It is _very_ firmly clamped on (after once making an abrupt sharp turn in the middle of a busy street and having the whole handlebar assembly rotate around the steering column I make sure of that).

I agree that the Brompton-style stiffener probably wouldn't help, because it gives no extra support against bending the handlebars perpendicularly to the stiffener rod. I think the only solution is stiffer bars. We put bending force into those bars that is completely unlike the job they are designed to do.

BK

 

[richa]

I vote handlebars


My vote is it being mostly in the handlebars. I think twisting an aluminum tube takes more energy then a human can supply with a 1 foot lever. But, I'm not a mechanical engineer so I maybe someone who is, or is simply knowledgeable in the area, can weigh in. Or perhaps already has....

If it is the tube, then one of bigger wall thickness could probably be found. If it's the handlebars, I there might not be beefier bars with the desired curve available.

I think the easiest solution is lower gearing. Then you can pedal faster to get the same energy input/speed, which will result in less torque and therefore less pulling on the bars, and less flexing. I already have a 11-24 cassette; maybe it's time to look into a smaller chainring as well, even though it would mean loosing the elliptical.

All that said, it certainly would be interesting to know where the flex is happening.

Rich

 

[Shahmatt]

Just drew it up to explain

Just drew it up to explain what I mean.

The red arrows indicate the bending motion of the handlebars.

Is this what you mean? If so then the stiffener rod works in tension to resist the motion. Please correct me if I'm wrong.

 

[Charles.Plager]

Hi Everybody,
I could very

Hi Everybody,

I could very easily be wrong here (I haven't been wrong in a while so I'm due... ). In my mind, I see the riser twisting. It could indeed be the handlebars flexing (in which case Shahmatt's suggestion may (or may not) help).

I don't have a great way of testing this (except, maybe firmly planting the wheel somehow and filming what happens when you push hard on the handlebars. If you have beefier handlebars available, you can try swapping them in and see if you notice a difference. (I'm guessing that it's easier to find beefier handlebars than it is to find a beefier riser).)

You're right that lower gear/spinning makes a big difference as far as reducing such energy loss. This is what I do, so I don't find that it's a big issue for me. As was also pointed out, if one moves your hands closer to the pivot point (the center of the handelbars), that should also reduce the effect (regardless of whether it's the riser or the handlebars themselves that are moving).

Cheers,
Charles

 

[Eric Winn]

On the Quest with front

On the Quest with front suspension, I would look at what is going on at the suspension area when you are yanking hard back and forth on your handlebars. The Quest front suspension always felt a little squishy to me. Not "bad" squishy, mind you just with a lot more "float" than the Silvio's front suspension. I liked the Silvio much better. It is kind of like an old Cadillac with a very soft ride vs a sports car's stiff ride. Both have suspension but cornering hard in an old Caddy is a bit more dramatic than cornering hard with a small sports car.

It would be interesting if Billy could ride both the fully suspended Quest and the newer model with just rear suspension back to back under this scenario to see what the difference in feel was.

Oh, and Charles my SRAM X9 Type 2 RD is a medium cage not a long cage so your "due counter" already triggered mister.

-Eric