Side loads on wheels

[G.Daniels]

i rode into a crack between new sidewalk and new assfault following an uptheriver gulf thunderstorm,
-clearly visible to the super before leaving for the tavern but less so when filled with gulf
rainwater and just lika tiddleywink zzzzzzzzap i wuz on the fresh cement minus several patchs of
treasured skin. no, ivan, my 36 hole rims will not mount a 6" curb at a 45 degree angle. BUT the rim
went undamaged.wonderful wonderful.

the serious preceeding discussion brings an element of bike tire construction to bear while
countersteering. the enhanced carcass built with sidewalls of aramid or kevlar gives a broader
platform(and more forgiving off clumsyness)to transmit downward force to the pavement rather than
wasting energy in transit to the sidewall forcing it over onto the asphalt rather than driving the
cycle forward. is that where the question winds up?

the converse of auto physics? for reasons of four wheels, less camber and no FI devices, and weight
greater than the rider.

the thought that goes into thinking about these subjects wud think well with animation. do fisher
and ritchey have such programs? how difficult is it to bring these(and wheel building) physics
excercises to life on the Dell?

 

[James Annan]

[email protected] wrote in message news:<kAyHa.3152$%[email protected]>...

>
> Hold it! Let's make a free body diagram and see where the loads arise. You cannot unilaterally
> push down on one bar-end unless you unload another area or lean off the bicycle to that side.

Yes I can, when I straighten my arm downwards I've got substantial mass (my body) to accelerate
upwards, if I push and pull with different arms then it's mainy a rotational effect. The only limits
to the magnitude of this force is my physical ability. I can see the front tyre squirming to the
side when I do this, which is direct proof that the side force exists at the ground. Of course I
can't maintain the force for long, but all I'm saying is that when bumping down over rough ground
the impulsive forces may be large (they definitely _are_ large, given fork compression and pinch
flats etc).

> I don't dispute that off center loads occur, only that they are not what you propose and are
> insignificant in magnitude.

Well, significance is in the eye of the beholder. You seem to be jumping ahead to address issues
that I'm not that interested in (wheel collapse) so I'll explain why I was thinking about this. It
is obvious that if the net reaction force at the ground is directed wide of the fork dropout then
there is a net downward pull at the other dropout. I'm only expecting this to be a relatively modest
force, something that a QR will routinely cope with (say a few hundred N) - and as you say, it is
probably a force that doesn't occur very frequently. Nevertheless, it adds to the other forces in
the system and it is still interesting to me to have a think about how big it could be. As I said,
the only obvious upper limit is that which causes a wheel collapse, although probably most
reasonably normal riding doesn't get too close to that limit.

James

 

[Kraig Willett]

"James Annan" <[email protected]> wrote in message
news:[email protected]...
> I'm only expecting this to be a relatively modest force, something that a QR will routinely cope
> with (say a few hundred N) - and as you say, it is probably a force that doesn't occur very
> frequently.

I would put it in the couple hundred newton range (based on the assumption that all the deflection
that I _measured_ for several separate wheels is due to a pure side load - something I am not
completely convinced of, BTW).

The setup/results can be seen/criticized at:

http://tinyurl.com/7o9q

Frequency of these events would depend on how often one rides out of the saddle, I reckon.

--
==================
Kraig Willett www.biketechreview.com
==================

 

[James Annan]

"Kraig Willett" <[email protected]> wrote in message
news:<[email protected]>...
> "James Annan" <[email protected]> wrote in message
> news:[email protected]...
> > I'm only expecting this to be a relatively modest force, something that a QR will routinely cope
> > with (say a few hundred N) - and as you say, it is probably a force that doesn't occur very
> > frequently.
>
> I would put it in the couple hundred newton range (based on the assumption that all the deflection
> that I _measured_ for several separate wheels is due to a pure side load - something I am not
> completely convinced of, BTW).
>
> The setup/results can be seen/criticized at:
>
> http://tinyurl.com/7o9q

I looked at that before, but didn't really have much to say as it didn't seem obvious that what you
had measured was directly relevant to what I am interested in. But now I've looked again and I do
see that you find a dynamic effect significantly adding to the pure lean effect (assuming I have
understood correctly - is this right?).

>
> Frequency of these events would depend on how often one rides out of the saddle, I reckon.

In the conditions I'm talking about, out of the saddle is pretty much a given, even with suspension
(which itself reduces the in-plane loading thus allowing greater speeds, while not affecting the out
of plane loading, the net result being relatively greater lateral forces).

James

 

[Kraig Willett]

"James Annan" <[email protected]> wrote in message
news:[email protected]...
>But now I've looked again and I do see that you find a dynamic effect significantly adding to the
>pure lean effect (assuming I have understood correctly - is this right?).

You are correct - lean angle is not responsible for all the deflection I measured.

Where is the rest coming from?

--
==================
Kraig Willett www.biketechreview.com
==================

 

[G.Daniels]

> So what. I do that to test whether a wheel has any spoke twist by coasting along slowly and
> leaning as far as I can off center while standing on one pedal. The wheel withstands this easily.
>
FILM AT 11!!

 

[G.Daniels]

this is a a no counter steer or lack of counter steer balance?

And it doesn't mesh with the feeling of the fronthub
> bending towards the pedals at turn in [this is a a no counter steer or lack of counter steer
> balance?]and popping back again once the turn starts

 

[Jobst Brandt]

Kraig Willett writes:

>> I'm only expecting this to be a relatively modest force, something that a QR will routinely cope
>> with (say a few hundred N) - and as you say, it is probably a force that doesn't occur very
>> frequently.

> I would put it in the couple hundred newton range (based on the assumption that all the deflection
> that I _measured_ for several separate wheels is due to a pure side load - something I am not
> completely convinced of, BTW).

> The setup/results can be seen/criticized at:

> http://tinyurl.com/7o9q

> Frequency of these events would depend on how often one rides out of the saddle, I reckon.

This test shows displacement of the rim out of fork center from side loads but doesn't isolate fork
deflection and wheel deflection. This could be done by clamping the steer tube (in a bicycle the
head tube) and hanging a side load on the axle with the fork axis horizontal.

Since the dynamic (riding) load is a torque applied at the RCP this is not readily separated but
requires some calculation.

Jobst Brandt [email protected] Palo Alto CA

 

[Mike S.]

<[email protected]> wrote in message news:2J1Ia.3511$%[email protected]...
> Kraig Willett writes:
>
> >> I'm only expecting this to be a relatively modest force, something that a QR will routinely
> >> cope with (say a few hundred N) - and as you say, it is probably a force that doesn't occur
> >> very frequently.
>
> > I would put it in the couple hundred newton range (based on the assumption that all the
> > deflection that I _measured_ for several separate wheels is due to a pure side load - something
> > I am not completely convinced of, BTW).
>
> > The setup/results can be seen/criticized at:
>
> > http://tinyurl.com/7o9q
>
> > Frequency of these events would depend on how often one rides out of the saddle, I reckon.
>
> This test shows displacement of the rim out of fork center from side loads but doesn't isolate
> fork deflection and wheel deflection. This could be done by clamping the steer tube (in a bicycle
> the head tube) and hanging a side load on the axle with the fork axis horizontal.
>
> Since the dynamic (riding) load is a torque applied at the RCP this is not readily separated but
> requires some calculation.
>
> Jobst Brandt [email protected] Palo Alto CA

Not being an engineer, wouldn't a better way to measure fork deflection caused by the wheel/tire be
to hang the weight at the rim?

By my thinking, that reflects the way the fork is being acted upon better than hanging the weight
at the axle.

Any thoughts?

Mike

 

[James Annan]

Kraig Willett wrote:
> "James Annan" <[email protected]> wrote in message
> news:[email protected]...
>
>>But now I've looked again and I do see that you find a dynamic effect significantly adding to the
>>pure lean effect (assuming I have understood correctly - is this right?).
>
>
> You are correct - lean angle is not responsible for all the deflection I measured.
>
> Where is the rest coming from?

Well, my guess is that the rider moving about can generate modest (momentarily) unbalanced torques.

James

 

[Chalo]

Tim McNamara <[email protected]> wrote:

> Frankly I have never been able to see why anyone bothers with trying to make this design
> [monobladed forks] work. The benefits seem relatively few.

Automobiles could hold their wheels in two-sided forks, too, but the benefits of such an arrangement
seem relatively few.

For a bicycle, the advantages of stub-axle wheels are pretty obvious. It would eliminate the need to
remove the wheels for practically any maintenance activity as is now the case. Although one would
not have to remove the wheels nearly as often as is now necessary, that operation could also be much
simpler with a stub axle wheel, with just a single fastener to undo and no messing around with the
chain or brakes. In addition, wheels for such a bike can be made interchangeable front and rear,
with no moving parts and only a simple torque-transmitting feature built into the wheels themselves.
They could be made in one piece from die-cast light alloy or injection-molded thermoplastic.

Imagine the ordeal if automotive wheel changes were as elaborate as bicycle wheel changes: When you
changed your car's wheels, it would also be necessary to do a brake job, likely realign the
driveshaft (chainline) and perhaps replace the rear differential (cassette) as well! To say nothing
of the possibility of having to *bend the frame* to accept the new wheels. With stub axle wheels,
you just bolt them on and go.

Now that disc brakes have come into common use (making braking independent of the rim), I think it's
inevitable that there will be a modular stub axle wheel system introduced sooner or later.
Single-sided wheels may not be the lightest or most structurally efficient way to go, but then
neither are suspension forks, and look how they have dominated the bicycle mass market.

Chalo Colina

 

[Chalo]

[email protected] wrote:

> James Annan writes:
>
> > If you like, perhaps you can consider them to be a succession of sharp steering corrections
> > where the bicycle is not leant in plane with the rider. This seems to me to be pretty much what
> > happens on some bumpy descents.
>
> No, not unless you are purposely trying to skid the wheel sideways. That is the way most non-crash
> wheel collapses are achieved. Skid on dirt, turn the wheel crosswise and hit an obstacle.

When I began my adult cycling career, I was fascinated at the frame whip I could perceive by
cyclically wagging the bars in the same frequency as the bike's flex. Once, in doing this, I caused
the rear wheel to collapse suddenly and completely underneath me. This happened at strolling speed,
on smooth pavement, with my butt planted on the seat. I believe it illustrates the distinct
possibility of exerting significant side loads on the wheels without skidding them or leaning them
out of plane with the rider cg.

While the circumstances of the failure do not constitute normal riding, neither are they entirely
anomalous IMO.

Chalo Colina

 

[Jobst Brandt]

Chalo Colina writes:

>> Frankly I have never been able to see why anyone bothers with trying to make this design
>> [monobladed forks] work. The benefits seem relatively few.

> Automobiles could hold their wheels in two-sided forks, too, but the benefits of such an
> arrangement seem relatively few.

> For a bicycle, the advantages of stub-axle wheels are pretty obvious. It would eliminate the need
> to remove the wheels for practically any maintenance activity as is now the case. Although one
> would not have to remove the wheels nearly as often as is now necessary, that operation could also
> be much simpler with a stub axle wheel, with just a single fastener to undo and no messing around
> with the chain or brakes. In addition, wheels for such a bike can be made interchangeable front
> and rear, with no moving parts and only a simple torque-transmitting feature built into the wheels
> themselves. They could be made in one piece from die-cast light alloy or injection-molded
> thermoplastic.

These are all secondary, function being the prime criterion for bicycle design because weight is so
highly important. Tiny hollow axles suffice for current road bicycle wheels and caliper rim brakes
are the mainstay, mainly for simplicity and light weight. Many designs on bicycles are different
than on most other machines mainly for weight reasons. A cantilever stub axle must be many times
heavier than current practice and the fork blade that supports it and disk brakes must be several
times heavier. You aren't going to sell that to road racers. It's amazing they put up with STI shift
levers that are 50% heavier than simple brake levers and downtube shifters.

> Imagine the ordeal if automotive wheel changes were as elaborate as bicycle wheel changes: When
> you changed your car's wheels, it would also be necessary to do a brake job, likely realign the
> drive shaft (chainline) and perhaps replace the rear differential (cassette) as well! To say
> nothing of the possibility of having to *bend the frame* to accept the new wheels. With stub axle
> wheels, you just bolt them on and go.

The car has so many things that rely on a high powered gasoline engine that there is no comparison
in any department.

> Now that disc brakes have come into common use (making braking independent of the rim), I think
> it's inevitable that there will be a modular stub axle wheel system introduced sooner or later.
> Single-sided wheels may not be the lightest or most structurally efficient way to go, but then
> neither are suspension forks, and look how they have dominated the bicycle mass market.

I don't think so. Their main advantage seems to be immunity to wet and dirt. Otherwise a disc brake
bicycle takes a hit on weight. For downhill racers, this is no problem and many MTB riders are
essentially interested in the downhill aspect of bicycling.

Jobst Brandt [email protected] Palo Alto CA

 

[Ryan Cousineau]

In article <[email protected]>, [email protected] (Chalo) wrote:

> [email protected] wrote:
>
> > James Annan writes:
> >
> > > If you like, perhaps you can consider them to be a succession of sharp steering corrections
> > > where the bicycle is not leant in plane with the rider. This seems to me to be pretty much
> > > what happens on some bumpy descents.
> >
> > No, not unless you are purposely trying to skid the wheel sideways. That is the way most
> > non-crash wheel collapses are achieved. Skid on dirt, turn the wheel crosswise and hit an
> > obstacle.
>
> When I began my adult cycling career, I was fascinated at the frame whip I could perceive by
> cyclically wagging the bars in the same frequency as the bike's flex. Once, in doing this, I
> caused the rear wheel to collapse suddenly and completely underneath me. This happened at
> strolling speed, on smooth pavement, with my butt planted on the seat. I believe it illustrates
> the distinct possibility of exerting significant side loads on the wheels without skidding them or
> leaning them out of plane with the rider cg.

I think it demonstrates once again that you are--and I mean this in the nicest possible way--an
extreme outlier in terms of the size, weight, and power of cyclists.

> While the circumstances of the failure do not constitute normal riding, neither are they entirely
> anomalous IMO.

It is an interesting data point. But you have repeatedly demonstrated that you can make bicycle
components fail in ways that virtually nobody else can. You see component failures that freeriders
would find spooky.

This is not meant as a dis' on you, Chalo, but your ability to make a component fail does not make
me believe that said component is underdesigned for most riders. You are not most riders, and must,
alas, choose your equipment accordingly.

--
Ryan Cousineau, [email protected] http://www.sfu.ca/~rcousine President, Fabrizio Mazzoleni Fan Club

 

[Ryan Cousineau]

In article <[email protected]>, [email protected] (Chalo) wrote:

> Tim McNamara <[email protected]> wrote:
>
> > Frankly I have never been able to see why anyone bothers with trying to make this design
> > [monobladed forks] work. The benefits seem relatively few.
>
> Automobiles could hold their wheels in two-sided forks, too, but the benefits of such an
> arrangement seem relatively few.

Except weight. Automobiles could hold their wheels in two-sided forks, but they have lots of room
and necessary superstructure inboard of the wheels from which to hang suspension, drive, and
steering components. Bicycles are not automobiles, and have nothing beside the wheels except
other bicycles.

> Now that disc brakes have come into common use (making braking independent of the rim), I think
> it's inevitable that there will be a modular stub axle wheel system introduced sooner or later.
> Single-sided wheels may not be the lightest or most structurally efficient way to go, but then
> neither are suspension forks, and look how they have dominated the bicycle mass market.

I'm assuming this was a modest proposal of sorts. For the front wheel, I think Cannondale may not
have a completely stupid idea. For the rear wheel, there would be some interesting things to sort
out regarding the chain line. I think it would work really well as long as riders started accepting
Q-factors about an inch or two wider than right now.

--
Ryan Cousineau, [email protected] http://www.sfu.ca/~rcousine President, Fabrizio Mazzoleni Fan Club

 

[Kraig Willett]

<[email protected]> wrote in message news:2J1Ia.3511$%[email protected]...
> Since the dynamic (riding) load is a torque applied at the RCP this is not readily separated but
> requires some calculation.

This is how the load was applied during my static tests (if I understand you correctly - the torque
being the side load applied at RCP acting at a distance from the steer tube boundary condition). If
I use the assumption that all the deflection I measured was due to a side load, I can do the back
calculations to determine the dynamically applied side load based on the static data, no?

It is the assumption that allows this calculation that I am not totally convinced of. Is there
something else going on that makes this a bad assumption?

For me, the test was interesting since one can compare the fixed boundary condition results that
Damon Rinard generated with the flexible boundary condition data I generated. The ordering of the
wheel stiffness was preserved, but the magnitudes are greatly reduced in my data - this makes sense
and is consistent with theory. It was also interesting to me that of the different wheels I measured
using my setup, the back calculations to determine "side load" were pretty tight despite drastically
different wheel designs.

To Jobst's point, though, my test does not separate the fork/wheel contribution to overall
deflection and this should be noted - different forks will provide different boundary conditions
which will ultimately affect wheel stiffness while riding. Fork design plays a role in "between the
pads" deflection (here is your chance Mark Hickey to openly criticize my thinking, instrumentation,
and methodologies).

--
==================
Kraig Willett www.biketechreview.com
==================

 

[S. Anderson]

"Mike S." <mikeshaw2@coxDOTnet> wrote in message news:Q22Ia.159750$eJ2.72664@fed1read07...
>
>
> Not being an engineer, wouldn't a better way to measure fork deflection caused by the wheel/tire
> be to hang the weight at the rim?
>
> By my thinking, that reflects the way the fork is being acted upon better than hanging the weight
> at the axle.
>
> Any thoughts?
>
> Mike
>

I would tend to agree. The distance from the axle to the rim would act as a lever increasing the
apparent force at the fork crown. I would guess it would be better to hang the weight from the
outer edge of the rim and measure the deflection at both the outer edge of the rim and the fork
at the axle while this weight is fixed on the rim. The measured deflection of the fork would have
to be increased based on the ratio of (crown-axle distance):deflection1 = (crown-rim
distance):deflection2. This deflection2 would be the deflection of the fork extended to the rim
edge. The true wheel deflection would then be total deflection at the rim edge minus the
deflection2. This may not be entirely correct since the wheel isn't really static in all of this,
but the error should be smaller than the error caused by not accounting for the lever of the
wheel radius.

Scott..

 

[S. Anderson]

"James Annan" <[email protected]> wrote in message
news:[email protected]...
> [email protected] wrote in message
news:<t%8Ha.2737$%[email protected]>...
>
> Certainly in normal riding I've no problem in accepting this. However I've heard (perhaps somewhat
> apocryphal) stories of tandemers folding up the front wheel while climbing slowly up a steep hill
> or otherwise manouevring slowly (especially when the front wheel has a disk brake and is therefore
> dished and relatively weak). This probably has more to do with large steering excursions and/or
> riders lurching about rather than substantial leaning of the bicycle.
>
> Another way of approaching the question would be to ask: what sort of side loads will a wheel
> stand before it does fail? Obviously it will also depend on the simultaneous in-plane load.
> There's no question that MTB wheels do see some side loads, this may be better considered as a
> case of near-crashing rather than just riding along. I think it's fair to say that _some_ tacoed
> wheels are probably the cause of a crash, rather than its result. Ie the rider would have expected
> to stay upright but the wheel folded up.
>
> James

When I was working in a shop, we used to fool around and see how far we could lean a bike over and
coast without falling. The lean angle (not really a lean angle..more of a balanced coast) was
surprisingly close to horizontal, certainly more than 45 degrees. We would basically stand on the
crank, not straddling the bike at all, and hold the bars with one hand. We weighed probably 175lbs
and we came close to collapsing poorly built wheels this way. You could actually see the wheel
detensioning and beginning to taco. However, we never actually caused a failure. Divide that weight
in half, 90 lbs roughly for each wheel. The wheels were not horizontal, say somewhere between 45
degrees and 60 degrees (conservative..on some of our failed coasts we'd actually ground the opposing
pedal). So there is an additional mitigation of deflective load from propagation of force through
the hub and spokes into the vertical plane of the wheel. And we still didn't collapse even poorly
built wheels. And these types of loads would never be approached in regular riding, except as Jobst
has pointed out, in a crash or near-crash situation. The only way I have ever personally seen a
wheel taco while in use was during a mountain bike ride in a sliding rear-wheel situation where the
wheel hit a berm/rock in mid-slide..the rider stayed up miraculously, but could not continue
obviously. He had all his weight on his outside, lowered pedal and when he hit, he hit the seat with
his ass and the ground with his free foot. There must have been considerable side force in that
near-crash. Certainly the wheel tacoed before the crash would have occurred..he probably would have
ridden it out if the wheel hadn't tacoed. I cannot imagine a front wheel collapse in this manner
without a huge steering input as you say, at quite a low speed that would probably end in a
foot-down fall over. It's possible to do the same thing with the brakes on..perhaps a sharp turn, a
relization that something bad is about to happen, a grab at the front brake, the wheel tucks under
against the riders force trying to keep it from tucking under and the wheel folds. Again, this could
only happen at walking speed or less.

Scott..

 

[Dianne_1234]

Could these test results be used to approximate the contribution of the fork in Kraig's set up?

http://www.sheldonbrown.com/rinard/rinard_forktest.html

[email protected] wrote in message news:<2J1Ia.3511$%[email protected]>...
> Kraig Willett writes:
>
> >> I'm only expecting this to be a relatively modest force, something that a QR will routinely
> >> cope with (say a few hundred N) - and as you say, it is probably a force that doesn't occur
> >> very frequently.
>
> > I would put it in the couple hundred newton range (based on the assumption that all the
> > deflection that I _measured_ for several separate wheels is due to a pure side load - something
> > I am not completely convinced of, BTW).
>
> > The setup/results can be seen/criticized at:
>
> > http://tinyurl.com/7o9q
>
> > Frequency of these events would depend on how often one rides out of the saddle, I reckon.
>
> This test shows displacement of the rim out of fork center from side loads but doesn't isolate
> fork deflection and wheel deflection. This could be done by clamping the steer tube (in a bicycle
> the head tube) and hanging a side load on the axle with the fork axis horizontal.
>
> Since the dynamic (riding) load is a torque applied at the RCP this is not readily separated but
> requires some calculation.
>
> Jobst Brandt [email protected] Palo Alto CA

 

[G.Daniels]

Bicycling Science, Second Edition -- by Frank Rowland Whitt (Author), David Gordon Wilson (Author);
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