Drilling holes in CF frames to save weight

[alienator]

1/10th scale electric cars weight from 2-8 lbs...and go from 15-100+ mph. on road courses, the barriers are typically wood or concrete. so they go, for example, 55mph to 0mph INSTANTANEOUSLY. the carbon chassis and compnents sometimes break, sometimes don't. these vehicles are as much toys as our bikes...and hardcore r/c racers will spend thousands on their rig...and thousands more per year simply on new batteries, tires, wheels, and parts. like cycling, they have professionals that race them for a living and are wealthy.

Wow. Instantaneously, eh? So, like, no time elapses during the acceleration from 55mph to 0mph. Wow. Impressive. Those cars must be really stout to withstand an infinite impulse.

Besides the obvious physics errors, you're also wrong by implying that somehow the dynamics you allude to in those massively huge RC car crashes are somehow scalable. They're not. So to compare the horrifically violent RC crashes to the obviously pedestrian forces involved in lowly cycling is both a logical and a technical mistake. The two situations aren't even remotely related. Ok, RC cars do have wheels, but the similarity stops about there.

Hopefully Boeing engineers didn't use their "experiences" and "knowledge" from RC car "engineering" with CF to design the 787 Dreamliner.

[drainyoo]

Im amazed that so many people took the OP seriously.

[vxracer]

I tried to drill my carbon shoes out, but it hurt my feet too damn bad. Now my socks get wet when I step in a puddle.

[MrCurrieinahurry]

drainyoo well said
tikka

[celerystalksme]

1/10th scale electric cars weight from 2-8 lbs...and go from 15-100+ mph. on road courses, the barriers are typically wood or concrete. so they go, for example, 55mph to 0mph INSTANTANEOUSLY. the carbon chassis and compnents sometimes break, sometimes don't. these vehicles are as much toys as our bikes...and hardcore r/c racers will spend thousands on their rig...and thousands more per year simply on new batteries, tires, wheels, and parts. like cycling, they have professionals that race them for a living and are wealthy.

Wow. Instantaneously, eh? So, like, no time elapses during the acceleration from 55mph to 0mph. Wow. Impressive. Those cars must be really stout to withstand an infinite impulse.

Besides the obvious physics errors, you're also wrong by implying that somehow the dynamics you allude to in those massively huge RC car crashes are somehow scalable. They're not. So to compare the horrifically violent RC crashes to the obviously pedestrian forces involved in lowly cycling is both a logical and a technical mistake. The two situations aren't even remotely related. Ok, RC cars do have wheels, but the similarity stops about there.

Hopefully Boeing engineers didn't use their "experiences" and "knowledge" from RC car "engineering" with CF to design the 787 Dreamliner.

oh geez...take some laxatives...

of course it's not mathematically instantaneous. but the time it takes from 55 mph to 0 mph is quite small compared to a bicycle crashing, where the impact usually does not involve the bike coming to a complete stop immediately but rather continuing along on some trajecory in a chaotic manner.

i don't doubt that the RC example is not scalable to bicycle level sizes...but the point was, i was responding to a fellow that said the those "toys" do not experience forces close to those of forces experienced by a bicycle hitting a pothole at 35mph or whatever he said.

[RollinOn27s]

of course it's not mathematically instantaneous. but the time it takes from 55 mph to 0 mph is quite small compared to a bicycle crashing, where the impact usually does not involve the bike coming to a complete stop immediately but rather continuing along on some trajecory in a chaotic manner.

i don't doubt that the RC example is not scalable to bicycle level sizes...but the point was, i was responding to a fellow that said the those "toys" do not experience forces close to those of forces experienced by a bicycle hitting a pothole at 35mph or whatever he said.

Apparently you missed Milano-Sanremo this year.

And Marcus Burghart's dog incident.

[alienator]

i don't doubt that the RC example is not scalable to bicycle level sizes...but the point was, i was responding to a fellow that said the those "toys" do not experience forces close to those of forces experienced by a bicycle hitting a pothole at 35mph or whatever he said.

His point was likely that RC stuff bears almost no relevance at all to bicycle stuff and offers zero intellectually illuminating points as they may regard drilling holes in CF bicycle frame members.

[alienator]

Apparently you missed Milano-Sanremo this year.

And Marcus Burghart's dog incident.

Yes. Exactly. And as it happens, since the mass of an RC toy car is miniscule compared to a bike rider system...what roughly 1/100 or so...the forces a tiny little toy will experience will be roughly two orders of magnitude less.

[drainyoo]

I tried to drill my carbon shoes out, but it hurt my feet too damn bad. Now my socks get wet when I step in a puddle.

I drilled holes in my tires once to get rid of some weight. It didn't work out too well.

[HammerTime2]

I drilled holes in my tires once to get rid of some weight. It didn't work out too well.

Too bad you didn't have run flats.

By the way, the real savings on drilling water bottles is not the weight of the removed plastic, rather, it's the water weight savings.

[Gregorio]

celerystalksme,
Just wondering how many RC operators have been injured when there car/helicopter/plane/boat or model rocket failed under these unimaginable forces of stopping on a dime.
Stop the madness! Time to Lock this one

[ergott]

Learn some physics. F=MA. Assuming a similar acceleration/deceleration, the mass is 25 - 100 times smaller in the toys your are talking about making the forces 25 - 100 times less. Hitting a pothole on a bike that bottoms out the tire will produce a larger force on the frame of a bike than any RC experiences. We've al seen carbon bike failures even when the whole frame is unmodified causing serious injury, why on earth would you even consider weakening one to save .5g??!!

-ERic

[chrism]

I don't even know why we're comparing the forces in bikes and RC cars. The structures are totally different too, so there really is no comparison. I can only assume that if people are drilling out the car chassis and not breaking them that they must be overbuilt in the first place - not something I'd geberally say about any of the <1kg frames we talk about on here.

[slvoid]

As a mechanical engineer, I find celerystalksme's comments absolutely frightening. Comparing an 8 lb car going 80mph and a 160lb human being going 40mph is absolutely insane.

WITHOUT going into the force vectors and stresses involved in two COMPLETELY DIFFERENT structures, look at the energies involved. The kinetic energy of the human being is 11665J, the car has 4x less than that, even at twice the speed.

Hitting a pothole, you'll have to accelerate that mass upwards, remember F=ma? The sheer amount of inertia of the human being compared to the car is TWENTY times more.

With scaled models, the expoxy plays more of a role and as you scale it up, the carbon ends up playing a greater and greater role. Carbon is ANISOTROPIC. With metal, you drill a hole, and it will distribute stress around it. The carbon itself will not, and that's assuming he can drill a perfect hole w/o any stress risers and without tearing the fibers out. If it's a super light bike, chances are, the frame is already pushed to the limit.

I, for one, would not want to ride that death trap.

I'll put it in layman's terms. You know those giant bugs in movies that look like scaled up versions of real bugs? Well by linearly scaling the legs up, in reality, they'll be way too weak to support the similarly scaled up body. That's kind of how your little RC cars are like.

[celerystalksme]

As a mechanical engineer, I find celerystalksme's comments absolutely frightening. Comparing an 8 lb car going 80mph and a 160lb human being going 40mph is absolutely insane.

why?

now, i'm no engineer by a LONG SHOT! i struggled with physics as an undergrad and i was a biology major. but...when i've seen these RC cars crash, the go from insanely high speeds to zero in a split second. it seems like a very large portion of that kinetic energy is converted to something else! either that, or the poor RC car is accelerated in a direction 180 degees from the direction it was originally going...it just gets bounced backwards against concrete or whatever.

but when i've seen bike crashes (i haven't seen the dog incident or whatever someone mentiond above), when a bike crashes or a bike hits a pot hole...the bike and rider still have TONS of kinetic energy as they fly off and go flipping away...it seems like only a fractional portion of that kinetic energy is actually affected by the collision.

so in my non-physics mind, it doesn't seem unfathomable to entertain the idea that the carbon components on a rc car experiences forces similar to the carbon frame on a bike.

if the physics guru's know better, i stand corrected.

as for the scalability...as i already said, i don't doubt that the results experienced by a 8-12 inch long carbon chassis is the same as a carbon frame with many feet of material.