55MPH while UP HILL !! with my DH comp setup !!

[AussieJester]

...they pale in comparison to a hair drier Doc.
KiM

Yes, because hairdryers use centrifugal fans, not axial fans. A controller or hub motor will have a lot more flow resistance than a hair dryer too.

Point i am making John, is its not as strong as a hair drier as Doc stated it was...Simply clarifying that is all

I would prefer no fans in a frock, i think the blades and venting you have done is better method...obviously
its useless when going slow but thats not often when the heat happens is it?

KiM

 

[John in CR]

From what I found, hair dryers don't move all that much air. I found 40cfm and 60cfm. The difference is that you could stick a blow dryer in the sleeve of a shirt and it will inflate it and push air through, while a higher cfm rated computer fan won't. Blowing some air on the outside is about all an axial fan is good for in our use, and even then some puffs of wind from movement of the bike will likely negate their usefulness in that manner too. Axial fans are just about as useless cooling computers too, but don't tell the suckers that don't know any better and bought them because they were cool to look at. Put your high flow axial fans to use as desktop fans, because that's about all they're good for.

Ever wonder about the odd dust pattern on the heat sink with a fan blowing on it? That's because there's very little actual flow though there is some odd shaped turbulence patterns created off of those blade tips.

 

[Doctorbass]

Well done on the 55mph uphill Doc

but Hey John, The fan i showed you is still pushing 23.78CFM !!!

incredibe right!!!.. BUt i believe that!.. it's like an hair dryer !!

HAHA Your joking about the CFM being alot right Doc?
i can fart harder than 23CFM buddy, i have 10 pc fans
in my computer they are ~80cfm http://www.pccasegear.com/index.php?main_page=product_info&cPath=9_510&products_id=8284
point being, they pale in comparison to a hair drier Doc.

KiM

I am not joking about that 23.78CFM !... it's the real specs! but that fan is so small than it's still impressive!

If you really can fart harder than 23CFM.. then...eeeee ... i dont know what to say!

:wink:

 

[veloman]

...Like, I can hit 30mph up a 10-12% grade on my road bike, and only about 38-39 on the flats...

Can you really sustain 30mph up a 10% grade? I want to see pics of these legs, because that's impressive. I pass pedalists all the time and see very few doing 30 on the flats, and none coming close on the hills. I'm just wondering if I'm not running across the serious guys.

No, I can not sustain that kind of speed up such a hill for more than a few seconds. I consider myself quite a bit above average compared to the average competitive road cyclist when it comes to such hill sprints - I love sprinting and do TONS of them for years now. The power to my rear wheel, my highest recording was just over 2000watts, but I'd average about 1700-1800 for 10 seconds on a good hill sprint. That's at 176lbs, with a 20lb bike. I can go 0-30mph in ~5.5seconds.

As for sustained riding, I could average 24mph (340watts) over a rolling 10-25mile course, which is pretty typical for a serious rider, but no where near what a good pro could do.

I am definitely not the typical guy on a bike you see! (trying to be honest and humble is hard!) I pride myself on my riding, it's so much fun and I work so hard to be a strong rider. Most of the time I ride pretty normal, and go up hills slow as I'm probably resting in between sprints or just taking it easy.

 

[John in CR]

...Like, I can hit 30mph up a 10-12% grade on my road bike, and only about 38-39 on the flats...

Can you really sustain 30mph up a 10% grade? I want to see pics of these legs, because that's impressive. I pass pedalists all the time and see very few doing 30 on the flats, and none coming close on the hills. I'm just wondering if I'm not running across the serious guys.

No, I can not sustain that kind of speed up such a hill for more than a few seconds. I consider myself quite a bit above average compared to the average competitive road cyclist when it comes to such hill sprints - I love sprinting and do TONS of them for years now. The power to my rear wheel, my highest recording was just over 2000watts, but I'd average about 1700-1800 for 10 seconds on a good hill sprint. That's at 176lbs, with a 20lb bike. I can go 0-30mph in ~5.5seconds.

As for sustained riding, I could average 24mph (340watts) over a rolling 10-25mile course, which is pretty typical for a serious rider, but no where near what a good pro could do.

I am definitely not the typical guy on a bike you see! (trying to be honest and humble is hard!) I pride myself on my riding, it's so much fun and I work so hard to be a strong rider. Most of the time I ride pretty normal, and go up hills slow as I'm probably resting in between sprints or just taking it easy.

That's cool and impressive. I had a feeling you were serious. So what's the username, veloman, about? You go for records and stuff in those noisy hotboxes? If so, how does that work out cross training wise, assuming you spend most of your time on uprights?

John

 

[AussieJester]

From what I found, hair dryers don't move all that much air. I found 40cfm and 60cfm.

Link to test data on assorted number of hair driers cfm ratings thanks John

The difference is that you could stick a blow dryer in the sleeve of a shirt and it will inflate it and push air through, while a higher cfm rated computer fan won't. Blowing some air on the outside is about all an axial fan is good for in our use, and even then some puffs of wind from movement of the bike will likely negate their usefulness in that manner too. Axial fans are just about as useless cooling computers too, but don't tell the suckers that don't know any better and bought them because they were cool to look at. Put your high flow axial fans to use as desktop fans, because that's about all they're good for.

Interesting John, the whole pc industry is using the wrong fans too cool pcs... danm we are suckers aren't we...so, Uhm...what are you using on your PC John, to cool cpu, gpu and mobo chipsets?

Ever wonder about the odd dust pattern on the heat sink with a fan blowing on it? That's because there's very little actual flow though there is some odd shaped turbulence patterns created off of those blade tips.

Nope never John not on my pcs or those i regularly fix for others, i myself though John, haven't directly aircooled a pc since ~2001, i use high cfm axial fans mounted on a shrouds that eleiminate the fan "hub dead spot" and fitted to 360 & 240 Thermochill rads to cool the pc i built John. My useless axial fans are setup up in a pull config and have no trouble pulling large amounts of air through heat exchangers so my 1100MHz OCed cpu never goes higher than 12c above ambient, John, not to bad for useless axial fans IMHO

KiM

p.s don't forget that hair drier test data you said you have seen, keen to see that John...

 

[liveforphysics]

It's slowly evolving with PC video cards, and has almost entirely saturated modern laptops AFAIK (makes sense, very confined spaces in a lappy). Modern servers use blowers almost exclusively for air motion through the sinks, but use an array of axials for bulk air movement out the back of the case.

Both types of fans definately have their place, if you've got a largely unrestricted path for the air to move, nothing can touch an axial. If you're trying to push air through a restricted space, the blower's much higher head capability soon has the advantage. You will notice in most all higher budget modern PCs, you see almost exclusively round heatsinks now, closely mated with an axial fan (modified with higher pitch for better radial discharge), but the fan is housed only able to discharge radially. Shrowding this way lets them have increased flow performance against a higher pressure differential, and enables the use of a lot finer pitch fins on the sink than would otherwise be possible.

A lot of semi-axial designs out as well, they are using an axial type fan, but housed so that axial flow is not possible, so the housing enables it to increase the discharge head ability to move a volume of air through much finer pitched sink fins than axial alone could do, boosting suface area for energy exchange.

 

[AussieJester]

Yup, axial fans move heaps of air through my pc if i run them on 100% i have them all ~25% power so its oober quiet but still keeps pc nice an cool.

TBH though ...i am more interested in John showing me a link to support his hair drier cfm claims, i find it quiet extraordinary someone would take that much time to conduct tests on a range of 'appliances' ....

KiM

 

[liveforphysics]

Yup, axial fans move heaps of air through my pc if i run them on 100% i have them all ~25% power so its oober quiet but still keeps pc nice an cool. HAHA some fail setups there Luke, could of at least found some decent non axial setups that use copper heat sinks not aluminium. aluminium suck ass on heat sinks buddy copper pwnz it by a large margin

Ehh, I spent roughly 30 seconds just finding a few examples.

It's interesting, but in the server world, you spend $15,000 on a server, and you get super loud ass fans on crude rough extruded alumium heatsinks. In a datacenter with total dust control in a sealed enviroment, it actually works out very well from the bump up in surface area. The same setup in a home with dust, smooth copper would be a way better choice, but getting way off topic now. lol


Just throwing a bit of dust filter over the inlet of an axial cuts the flow down by a whole lot, some dust filters over the inlet or discharge side of a blower with a decent A/R ratio, and you get a very small reduction in flow. Pushing loads of air past nothing doesn't get much bang for your buck for the air you're pushing, pushing a lesser amount of air all channeled up close and personal with the heatsink surface can work loads better (perticularly in situations with minimal space). But again, it's totally application dependent. Definately a place for both types of fans.

 

[AussieJester]

but getting way off topic now. lol

True..and air cooling PC talk does same thing to me non HD video do for you, Luke!... oh wait, no thats wrong, it doesn't give me herpes, it makes me bored, uninterested and sleepy It's what sex with just one wiminez a day does for you! hang on...or is it dragging V8s in the Civic...I need to make a list too keepz up ... :lol:

KiM

p.s ever seen one of these Luke? Made it few years ago, could get below ambient water temps with it all year round, hooked to mains water so it topped itself up, i used a toilet bowl float mechanism to trigger refilling...

 

[liveforphysics]

Never seen one of those crazy things. I'm guessing it has some airstones at the bottom to make a backwards mini evaporative cooling tower?

 

[AussieJester]

Never seen one of those crazy things. I'm guessing it has some airstones at the bottom to make a backwards mini evaporative cooling tower?

They are known as a bong coolers, swamp coolers or evaporative cooling towers, very surprised you haven't seen one before buddy, mines was a lil more 'flash' than most you see on the net i must admit anwyaz back on topic...

KiM

 

[John in CR]

Here you go AJ. The initial poke around was some guys' estimates for use in DIY foundries, so found some stuff for you. Regular home blow dryers don't quote cfm in their specs, so we have to look elsewhere:

Commercial hand dryer 130cfm - reasonable to expect home blow dryers are less due to the smaller cross-sectional area of the exhaust. http://absupply.net/bradley-2873-hair-dryer-5472.aspx

Here's a pet blow dryer with 85cfm high and 42cfm low settings - probably most comparable to the pistol type home blow dryers - http://www.wikio.com/product/metrol...high-42-1-2-cfm-9000-fpm-low-165261502,g.html

pet blow dryer 25cfm - Comparable velocity to larger dryers, but they achieve it due to the smaller diameter exit. This one is likely comparable or better in actual flow to the travel type blow dryers or those crappy ones in hotels. http://www.northcoastpets.com/metro_flexidri.htm

What's probably given you the false impression is that blow dryers have a much more focused flow, so the velocity is much greater for the same cfm compared to your computer fans. I should mess with you about "I don't use air cooling", yet you have 10 fans in your computer.

If you don't believe typical axial fans flow very little once a little restriction is introduced, just try it yourself. I don't keep up with the latest fads in computer, but it looks like they're coming around with better fans, though even Luke linked one where the fan part is mostly bling, unless that's one of the newer hybrid axial/radial type of blades. The last time I opened a computer, the processor heat sink had an axial fan snapped flush to it which is extremely ineffective for actual flow through the fins , and probably is something like 10% or less for actual flow vs free air cfm.

The bottom line is that you're going to be very hard pressed to find an effective use for an axial fan with our ebikes. Yes some flow is better than none, but a radial (centrifugal) fan (blower) is far better. The little fans Doc linked do a nice cfm for that size, and just maybe the double stack fan approach will do better with some restriction, though it's unlikely it could compete with a blower of similar power. Just looking at cfm is very misleading, unless you're comparing different blower type fans.

John