Strength of a wheel?
do...@zing.icom43.net
Preseumably a 15kg bike can carry, say, a 140kg rider plus maybe 10kg
luggage. If the rider is stting fairly upright most the weight will be
on the back wheel, say two thirds, so the back wheel will be handling
at least 150kg x 0.66 = 100kg, which seems rather a lot. Anecdotally it
is spokes that seem to go first, rather than bearings or rim, or is the
tyre the weakest link?
Anyway, does anyone on this list have any knowledge of this, for which
I would be most grateful.
Doug.
A Muzi
I don't know anything about hard numbers for impacts.
Montgomery Young, who built wheels at Condor, had an
'independent' test of 4000 pounds static load on a 1 pound
wheel of his without deformation. They used that in
advertising 35 years ago.
Impacts may be difficult to describe numerically. Similar
crashes can leave a cracked frame but a perfect wheel, the
other way around, frame and wheel OK with a dead fork or any
combination including split/cracked rims, potato chip rims
etc. Seldom broken spokes though.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
Earl Bollinger
news:1135666630....@g43g2000cwa.googlegroups.com...
built and tensioned 36 spoke wheel is able to support approximately 400kg.of
weight. That works out to be about 880 pounds. Lots of caveats of course,
the quality of materials, things like bumps in the road can put the loads
way over that momentarily.
I see it asit is the spokes that tend to go first. Rim usually gets tacoe'd
on the nasty holes or bumps or when several spokes let go at about the same
sime.
700c wheels seem to be more fragile versus the regular ATB or MTB 26"
wheels. The simple stamped steel rims seem to hold up better than the fancy
high tech wheels at these weights without breaking spokes.
I took up building my own wheels, so I could decide on the components I want
to use in them. I weighed more than most custom wheel builders would
warranty their wheels with me, so it just wasn't worth it to buy the
expensive good wheels if there wasn't much of a warranty on them. The store
bought rear wheels were almost self destructing while you tried them out.
I see it that the rear wheel needs 36 spokes, a 40 or 48 spoke tandem wheel
is even better, and a really good high quality stiff rim, and a good hub of
course (accurate spoke hole drillings), and of course good spokes. The stiff
rim helps distribute the loads over more spokes, spreading out the stresses
more.
I use a steel framed 700c32 wheel equipped touring bike for my, 23 mile one
way, commutes to and from work (when the weather isn't too bad). That way I
can get in lots of bike riding time without impacting on my family life too
much. Anyway, when I first started, I could expect to have spokes break
almost daily. I bought one cheap wheel, and it lasted one ride and popped
five spokes in a long left easy turn on me. So eventually I gave up and
started building my own wheels, and since then I have gotten it up to around
1,000 miles or so before I notice I had a spoke pop on me. Amazingly enough
the last time I had a spoke pop, it was on the front wheel. So I had gotten
quite a few thousand miles off of the rear wheel i am using now so far. So I
am getting better at it (knock on wood). I don't know if I'll ever get it
much better as there are several places on the roads that are really bad and
you literally have to slow down to avoid destroying anything or crashing.
Very uneven concrete road slabs on a stretch of road where the 80 wheelers
have really beaten it to death play havoc on your bike's wheels.
When I first started, my total all up commute to work riding weight exceeded
140kg, but now it is under that. So maybe there is a theoretical 140kg max
limit on 700c wheel equipped bikes. I used to break spokes a lot more way
back then. Or it is just my imagination running amok and I am actually
building wheels better than I can buy.:)
Being on the safe side I think going to a 40 or 48 spoke tandem wheel (you
need to put in a shorter axle for regular bikes) is really the way to go, as
these wheels handle loads and stresses much better than the 32 or 36 spoke
wheels. But that is probably overkill for most purposes.
Every now and then I see a picture of a Asian rider on his bike with a
"impossible to carry load" going off to market and I think that there is
hope yet. Maybe those cheap 40 spoke stamped steel old timey 28" rims is
still the way to go for sure.:)
On some oraganzied rides I have seen a number of heavy riders weighing
upwards of 160kg or more riding little road bikes with 700c23 or 25 tires.
So since they are doing it what the heck, anyone can.
jim beam
you're referring to fatigue strength rather than static strength or
stiffness. the best improvement for fatigue strength of spokes is to
use a high quality "brand" spoke, or address the /real/ issue by using a
wheel with straight pull spokes rather than elbowed. 100kg is not a
massive load.
dvt
> do...@zing.icom43.net wrote:
>> Does anyone know how much load a typical cycle wheel can handle?
>> Preseumably a 15kg bike can carry, say, a 140kg rider plus maybe 10kg
>> luggage. If the rider is stting fairly upright most the weight will be
>> on the back wheel, say two thirds, so the back wheel will be handling
>> at least 150kg x 0.66 = 100kg, which seems rather a lot. Anecdotally it
>> is spokes that seem to go first, rather than bearings or rim, or is the
>> tyre the weakest link?
> you're referring to fatigue strength rather than static strength or
> stiffness.
From whence do you infer this? I don't see any mention of high N cyclic
loading in the OP. I'd guess he's asking how heavily he could load his
bike for the occasional trip, not how heavily he could load the wheel
consistently and still expect X miles of life.
--
Dave
dvt at psu dot edu
dvt
> Does anyone know how much load a typical cycle wheel can handle?
> Preseumably a 15kg bike can carry, say, a 140kg rider plus maybe 10kg
> luggage. If the rider is stting fairly upright most the weight will be
> on the back wheel, say two thirds, so the back wheel will be handling
> at least 150kg x 0.66 = 100kg, which seems rather a lot. Anecdotally it
> is spokes that seem to go first, rather than bearings or rim, or is the
> tyre the weakest link?
This is a loaded (pun intended) question.
A typical 36-spoke wheel with spokes at 100 kgf will take around 300 kg
static radial load before the bottom spokes get slack. The tension in
the bottom 4 spokes is reduced, and if two spokes take 100 kg each and
the other two take a little less, you get a number in the neighborhood
of 300 kg. Naturally, different tension or spoke count will produce a
different load capacity. A stiffer (i.e. deep section) rim may
distribute the load over more spokes, so the static load capacity increases.
Once the spokes go slack, you're relying on the strength of the rim to
resist buckling. A classic box-section rim will probably give you very
little load capacity beyond the slack spoke limit. Some rims (i.e. deep
section rims) are stronger than others in this respect.
If you load a wheel with 300 kg and roll it over a bump, the momentary
load may be more than the wheel can support and the wheel may collapse.
If you load the wheel with 100 kg, you will get more resistance to
collapse. And so on and so forth.
Suspension (i.e. bigger tires, etc) also increases resistance to
collapse since the peak load induced by riding over a bump is decreased.
And finally, a bicycle wheel is not very strong laterally. So if you
have a multi-track vehicle (i.e. a trike), and you load the wheel close
to its static capacity, the wheel will be prone to collapse when you go
around a corner.
It's pretty hard to answer your question with the info you've given. And
we haven't even discussed long-term durability, but that's another can
of worms. If you fill us in with the details of your intended
application, we might be able to give you an answer that is more useful.