Author Topic: Dry arse.  (Read 4137 times)

Re: Dry arse.
« Reply #75 on: October 19, 2019, 08:28:48 am »
Water is flung off the wheels tangentially. Drawing a tangent off the rear wheel up past the end of the bag probably reaches your upper back, whence it trickles down.

Re: Dry arse.
« Reply #76 on: October 19, 2019, 08:30:27 am »
I doubt there’s an explanation that would satisfy you, but at least your photo shows your objection doesn’t come from not wanting to attach stuff to the bike.
The tyres throw water into the air and you ride into it.  There’s no static diagram and there’s no magic.  You’ll still get wet, just not as wet and not as quickly. That’s the experience of so many, it’s hard to see how yours could be different.

Re: Dry arse.
« Reply #77 on: October 19, 2019, 10:44:58 am »
The Real answer is an up wrong trike .
Four wheels move the body, two wheels move the soul  three wheels Nurses !!!

Re: Dry arse.
« Reply #78 on: October 19, 2019, 12:40:55 pm »
One of the problems I've had on long rides in the wet before is that my knees get irritated by the waterproof trousers rubbing over the top of the knee cap.
Shorts are not the same as trousers.

Trousers have a considerable length of material between ankle and knee to drag, especially when there's a bit of dampness to encourage it to stick. They also are frequently tight or fastened around the ankle to keep the end out of the chainset.
As a result, the material across the knee can be under a fair bit of tension when the knee is bent, which provides extra friction for skin irritation, and may also cause the kneecap to be dragged about in a manner that may cause eventual problems.

5 cm or so of loose material extending past the bent knee is under no tension, and is very unlikely to cause any problem.

On the other hand, as I said back in August, when the top of the knee is exposed at the top of the pedal stroke. it gets wet. At the bottom of the pedal stroke, the end of the shorts leg drops down over the wet knee, getting the inside of the shorts leg wet. It then drags up as the pedal rises, spreading the dampness up on to that part of the leg that is covered at the top of the pedal stroke, which in turn gets the inside of the shorts leg damp higher up.
Spend a long time pedaling in the rain, and the dampness spreads right up the leg.

quixoticgeek

  • Mostly Harmless
Re: Dry arse.
« Reply #79 on: October 19, 2019, 03:58:56 pm »

Update.

My arse.

It is dry.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Dry arse.
« Reply #80 on: October 19, 2019, 04:36:00 pm »

Update.

My arse.

It is dry.

J
You have to tell us how....

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Dry arse.
« Reply #81 on: October 19, 2019, 04:46:23 pm »


Can someone explain the physics of how water gets from the wheel to the small bit of arse below my jacket, past this saddle bag?

J
It did with my (similar) Blackburn seatpack. My shoulder blade area still got the spray, and it trickled downwards
With some setups it doesn't even need to trickle down - you have a huge low air-pressure zone around your bum, so inevitably some water will get sucked in. The effect may even be worse at higher speeds - I haven't seen any science on the matter.
This only happens if you haven't eaten the beanz.  :D
A cup of tea is the perfect bridge between real life and cake.

Zed43

  • prefers UK hills over Dutch mountains
Re: Dry arse.
« Reply #82 on: October 19, 2019, 07:21:26 pm »

Update.

My arse.

It is dry.

J
You have to tell us how....
Local Warming. Spray evaporating before reaching arse. (that, or a rare case of a dry audax day in .nl)

Kim

  • Timelord
Re: Dry arse.
« Reply #83 on: October 19, 2019, 07:33:36 pm »
The Real answer is an up wrong trike .

Those (well, any trike without mudguards, really) are mostly a way to distribute as much water as possible onto whoever's sneaking up behind you.  (DAHIKT.)
Careful, Kim. Your sarcasm's showing...

Re: Dry arse.
« Reply #84 on: October 20, 2019, 11:19:49 am »
But on a up wrong trike in  wet weather . You do get to wheel suck behind  conscientious bike riders . Who fit BFO mudguards and flaps . I do fit a front mudguard because I hate wet feet  and its cheaper and less aggro than replacing 7 speed transmission components .   
Four wheels move the body, two wheels move the soul  three wheels Nurses !!!

Re: Dry arse.
« Reply #85 on: October 20, 2019, 11:38:13 am »




Can someone explain the physics of how water gets from the wheel to the small bit of arse below my jacket, past this saddle bag?

J

wake vortex.



you can see that some of the air is moving back towards the truck. It is this that allows people to ride a bicycle at ~150mph behind a suitable vehicle; they are literally being pushed along. It is also this which

- makes the back of vehicles dirty
- lets CO from vehicle exhausts into car cabins when the rear windows are open
- gets your arse wet, if you are throwing water into this part of the airflow

IMHO mudguards are a really good idea. Bad mudguards are not.

If you have dry bum now, what made the difference?

cheers

fboab

  • It's a fecking serious business, riding a bike
Re: Dry arse.
« Reply #86 on: October 20, 2019, 12:28:38 pm »
It didn't rain.
TSS is not Total Sex Score, Chris!

quixoticgeek

  • Mostly Harmless
Re: Dry arse.
« Reply #87 on: October 20, 2019, 06:10:14 pm »
It didn't rain.

Certainly pissed down where I was.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Dry arse.
« Reply #88 on: October 21, 2019, 10:32:59 am »




Can someone explain the physics of how water gets from the wheel to the small bit of arse below my jacket, past this saddle bag?

J

It doesn't matter why.  It's an emprical result based on extensive testing.  That is far more useful than a theory!

quixoticgeek

  • Mostly Harmless
Re: Dry arse.
« Reply #89 on: October 21, 2019, 11:25:54 am »
It doesn't matter why.  It's an emprical result based on extensive testing.  That is far more useful than a theory!

http://www.catb.org/jargon/html/C/cargo-cult-programming.html

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Dry arse.
« Reply #90 on: October 21, 2019, 11:39:10 am »




Can someone explain the physics of how water gets from the wheel to the small bit of arse below my jacket, past this saddle bag?

J

As well as getting flung upwards and forwards the water is also flung outwards. The further from the point where it leaves the wheel the larger the plume.  Your saddle bag being quite far from the tyre means a large plume of water and/ or mud is able to fly over the top or around your saddle bag into the low pressure behind your arse, then pulled in via the air vortices flowing into that gap. In effect your saddle bag only stops a relatively small amount of the water being picked up by your tyres and flung in your direction helped along by air pressure and currents.

quixoticgeek

  • Mostly Harmless
Re: Dry arse.
« Reply #91 on: October 21, 2019, 03:21:35 pm »

As well as getting flung upwards and forwards the water is also flung outwards. The further from the point where it leaves the wheel the larger the plume.  Your saddle bag being quite far from the tyre means a large plume of water and/ or mud is able to fly over the top or around your saddle bag into the low pressure behind your arse, then pulled in via the air vortices flowing into that gap. In effect your saddle bag only stops a relatively small amount of the water being picked up by your tyres and flung in your direction helped along by air pressure and currents.

Funky!

Thank you. That makes sense.

J
--
Beer, bikes, and backpacking
http://b.42q.eu/

Re: Dry arse.
« Reply #92 on: October 23, 2019, 03:50:11 pm »
If you want to have a dry arse, the rear mudguard has to extend below the rear axle's level otherwise the water will get flicked off of the tyre in a forward direction (towards your arse).

zigzag

  • unfuckwithable
Re: Dry arse.
« Reply #93 on: October 23, 2019, 04:23:48 pm »
If you want to have a dry arse, the rear mudguard has to extend below the rear axle's level otherwise the water will get flicked off of the tyre in a forward direction (towards your arse).

rear mudguard extending to ten o'clock position is enough, because it sits (ideally around 1.5cm) away from a tyre and makes a vertical tangent line with it. for protection of others - it needs to end lower and have a mudflap which ends around 5cm above the ground (mudflaps like "raw" are too short, fwiw). to have a whole group of riders with the right length mudflaps is zero (unless it's a special one-off exercise), so i don't bother myself either and avoid riding in groups on wet/muddy roads.
i'm trying to think of a quickly detachable front mudflap for my hack bike, for those rare wet rides - to keep my feet and drivetrain drier/cleaner.

Re: Dry arse.
« Reply #94 on: October 23, 2019, 07:19:58 pm »
If you want to have a dry arse, the rear mudguard has to extend below the rear axle's level otherwise the water will get flicked off of the tyre in a forward direction (towards your arse).

rear mudguard extending to ten o'clock position is enough

Or two o'clock from the other side!  ;)
Bread of heaven, bread of heaven.

zigzag

  • unfuckwithable
Re: Dry arse.
« Reply #95 on: October 23, 2019, 07:40:29 pm »
If you want to have a dry arse, the rear mudguard has to extend below the rear axle's level otherwise the water will get flicked off of the tyre in a forward direction (towards your arse).

rear mudguard extending to ten o'clock position is enough

Or two o'clock from the other side!  ;)
if the bike is photographed from the wrong side - yes.