Anyone using PowerPod on a Fat Bike with any success?

offpiste.reese
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Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Has anyone gotten the PowerPod setup for use on a Fat Bike? I talked to the PowerPod guys and they thought it would be doable, but I thought I would check to see if anyone was actually doing it. Thanks.
Ratman
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

The simple answer is, no, in my experience, it doesn't work. Please check your personal messages for details.
Velocomp
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

I can see no reason in principle that PowerPod would not work on this style of bike. Most certainly, there might be parameters set differently for the low tire pressure and also the wheel circumference, but I think that would be about it.

If there is data that shows the contrary I would sure like to see it...
John Hamann
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

I believe Ratman is referring to his issue with the iBike which was never resolved and is documented in this thread: http://www.ibikeforum.com/viewtopic.php ... 030#p19030

Is there a difference between the iBike's handling of on the fly corrections versus the PowerPod? That thread doesn't give me the confidence to give the PowerPod a shot for a Fat Bike application.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Sadly, two things happened:

1) I don't recall seeing the "ratman" response, so I did not follow-up with his final post.

2) The files in this thread are no longer available from our blog. If "ratman" is following this thread, I'd appreciate a new posting.

One statement made in the thread incorrect: Crr does NOT "go negative" during a ride. What I think was happening is something to do with the calibration of the unit, or perhaps its mounting angle on the bike. I won't be able to tell until I see the ride file.

While I do understand your concern about this particular thread (for which I feel bad about not responding), there is no reason to believe PowerPod won't work for fat bike applications.
John Hamann
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Ok. Thanks for the information.
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Ok, so I acquired a PowerPod to try out on my Fat Bike. I have used it for a couple of rides. The first couple, I think the cables may have been causing some airflow issues, but my last ride I zip tied them so that there should be smooth air hitting the PowerPod. I have attached the .ibr file from the ride. I can't attach the .tcx, it is bigger than 5 megabytes.

I see what Ratman was saying, the CRR from the ride file is showing as -0.0001. I have it set in the setup as 0.0211. Additionally, I have the tire circumference set to 2394, a value I pulled from the web. The .ibr file shows 23.74 miles whereas the .tcx shows 21.59. If I adjust the tire circumference to 2175, that would make the distances match up. Additionally, looking at the graph of coasting and braking, it's not realistic at all. Most of the descents on this ride were fire roads, so I pretty much let it rip and brake only when I need to. My normalized power shows as 159 for a TSS of 120, which seems low. My hrTSS was 187, usually my TSS and hrTSS are within 10-15% on this kind of ride, with long climbs and descents.

Any help with configuration to get this set up would be appreciated.
Attachments
iBike_12_03_2016_1418_24_Miles.ibr
(415.11 KiB) Downloaded 250 times
Velocomp
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Your PP was pretty badly miscalibrated. Wind readings were low, due to low wind scaling factor.

I used the "Analyze/Check Calibration" to correct the wind scaling factor.

I'm not sure why your Crr is negative, but I manually corrected it to 0.008, the value for fat bikes.

You can manually measure the circumference of your fat bike wheel, then input this manually into your profile. I don't generally trust GPS measurements, particularly in wooded areas.

Corrected profile and ride file are attached.
Attachments
Fatbike_12_03_2016_1418_24_Miles.ibr
(613.33 KiB) Downloaded 251 times
FatBike.ibp
(577 Bytes) Downloaded 244 times
John Hamann
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Thanks. I didn't do another calibration ride after clearing up the brake/shifter cables. Should have thought of that. I will do that.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Just load the attached profile and you should be able to skip the cal ride.
John Hamann
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Will do. Thanks.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by ronpei »

the most significant issue I see is rolling resistance. I use a variety of tire pressures depending upon conditions.also in any one ride I might be on smooth dirt, hay fields, sand, snow(and that is a whole other story), mud, etc and from my pedalling effort I know they are very different. I see no way the power pod or newton can estimate CRR in all of these circumstances So other than that one error the rest seems do able but depending upon the mathematical effect of CRR on the equation it can not be adequately estimated for the ride, and a cal ride is unlikely going to cover all of these circumstances under your wheels and as well varying tire pressure. Since I do not know the exact equation used in this application it is hard to estimate the error it might cause, but it must insert some error into the model.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Our new DCRR firmware dynamically measures road roughness, and should be quite helpful for the conditions you describe.

The cal ride does not measure road conditions; it measures tilt angle and (if you do it), wind factor.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by ronpei »

well I would love to believe you but the road vibration on a road bike is much different than a fat bike with 4-6 psi and a 4.5- 5 inch tire. A lot of any of this feedback would be eaten up by the tire and some by the suspension fork... so though I have no issues with the ibike on my road machines I do not feel it would provide me much useful info on my fat bike. Things like snow and mud do change the "road" vibration but typically not to rougher, rather smoother, but harder to push through. On my rides through snow it is something that I can only say you would understand after having experienced it, sometimes there is no way to get traction to move, some where you are snow ploughing, and other times it is like riding on white pavement, and this can happen in the same ride. It is my understanding from a mathematical point of view the 2 most significant factors in the calculation are CDA and CRR. At most fat bike speeds CDA may not be that big a deal but the CRR will swing dramatically and I have no idea what that range might be. So for that main reason I think the iBike may not be ideal in this situation.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

I'd love to see a ride file recorded with DCRR. That will tell the story.
John Hamann
ronpei
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by ronpei »

I fully agree John, I wish that was possible.. I am iBike only!
offpiste.reese
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by offpiste.reese »

Here are 2 files, the original and one that I did a Repair->Bad Tilt Calibration on for an hour cross race I did on my fat bike. It had varied terrain, rail trail, dirt, grass and a creek crossing that I rode. The power numbers were crazy high during the ride, I had just remounted the PowerPod and obviously didn't get it on the same as the last time. My normalized power before fixing was about 80 watts above my threshold. After fixing the file, it was within a couple of watts of my threshold power, which would seem about right. I will post more files as I ride more.
Attachments
iBike_12_10_2016_1253_10_Miles.ibr
Original Ride file
(183.1 KiB) Downloaded 217 times
CrossRace_12_10_2016_1253_10_Miles.ibr
Fixed file
(275.09 KiB) Downloaded 192 times
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

(Apparently, the iBike Forum software doesn't allow posting above a certain size, so I'm going to need to make the following thoughts across more than one post)

I've recently returned to this board and still would like a thoughtful and valid explanation from Velocomp to an issue that I've previously raised but has gone unanswered. This is regarding use of a Newton or a PowerPod on a fatbike for offroad/singletrack riding:

The March, 2015 edition of the Newton operations manual (which appears to be the latest version) states the following regarding "Typical" CRR values:

"Crr (coefficient of rolling resistance) measures the amount of opposing friction caused by road surface, tire type, and bearing friction. A low value of Crr means low rolling resistance. On a very smooth surface, such as those found at an indoor track, Crr can be 0.003. Asphalt roads have a typical Crr of 0.0055, and dirt roads can have Crr values of 0.008 or higher." (italics added by me)
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

Second part -- These CRR values have long been used by Velocomp in their support documentation (I bought my first iBike computer back in about 2009 and seem to recall the same values then), and since they were first offered years before fatbikes were being sold in any reasonable volume, it's safe to assume that these CRR values refer to ROAD tires/wheels.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

Third part -- These CRR values have long been used by Velocomp in their support documentation (I bought my first iBike computer back in about 2009 and seem to recall the same values then), and since they were first offered years before fatbikes were being sold in any reasonable volume (i.e., there may have been a few backyard mechanics in Alaska with them, but I'm talking about pre-Surly, Salsa, etc.), it's safe to assume that these CRR values refer to ROAD tires/wheels. It also seems fair to describe "average" road tires as being in the neigborhood of 1 and one-eighth inches wide, smooth or with a very modest tread pattern, and run at, maybe 80-120 psi (i.e., very firm). Based on this information, we can assume that use of a relatively narrow, smooth, high pressure tire on a "dirt road" can have valid "...CRR values of .008 or higher."

Now, let's look at fatbike tires -- I'll use mine as an example. I'm riding Surly Bud (front) and Lou (rear) tires which nominally measure 4.8 inches wide (i.e., HUGE compared to road tires, with FAR MORE surface contact), have 7mm tall traction knobs (i.e., FAR taller and more aggressive than those found on road tires), and are run with as little as 4-5 psi on dirt (i.e. "Ridiculously" low pressure levels, causing EXTREME contact and traction with the riding surface well beyond what even the huge width would suggest).
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

Final part -- Regarding the "typical" riding surface that a fatbiker might encounter, let me use my own "home course," Washington Valley County Park (aka, "Chimney Rock") in Martinsville, NJ as an example. With rare exception, the trails are covered with disorganized, 1-2 inch diameter rocks, with larger rocks and even boulders thrown in to make it interesting. There are numerous short, steep, and rocky climbs. I think it's fair to say that these trails would be impassible using any four-wheeled motorized vehicle other than an all-wheel drive Hummer...maybe -- they're THAT rough.

So, I once again pose the following question. If a CRR= 0.008 ("or higher," per the Newton operations manual) is an appropriate value for narrow, relatively smooth road tires inflated to high pressures when ridden on normal dirt roads, how could a CRR of 0.008 be "THE VALUE" (Mr Hamann's words in his December 6th post above) for fatbike tires 4-5 times as wide as typical road tires, with HUGE, high rolling resistance knobs, ridden on trails that make most dirt roads look smooth? Please, I'd really like to understand how this is possible...
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

We will be doing some testing with fat bikes and afterwards will update our documentation and recommendations as needed.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

:)
Velocomp wrote:We will be doing some testing with fat bikes and afterwards will update our documentation and recommendations as needed.
Thanks, I'm happy to hear that you'll be investigating this issue because the "one-size fits all" approach just doesn't make sense. Furthermore, I strongly suspect that trying to use higher CRR values more appropriate for fatbikes is causing the "on-board"/"during-the-ride" reconfiguration to negative CRRs that I and others have reported.

When can we expect to hear more on this subject?
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Newton's Third Law, upon which all our products are based, is about as "one size" as it gets, no matter what kind of bike is being used.

Your supposition is appreciated but it is incorrect.

Once we gather more data from fat bikes we will report our findings.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by ronpei »

there are a few subtle issues that fat bikes encounter which are not the same for a road bike, The rolling resistance can change dramatically depending upon what you are rolling on or through, this is not an real issue for a road bike. In any ride I can go from smooth easy rolling to snow that actually slips under the wheels (hence no traction) to hard to pedal through deep snow. I may ride one set of conditions with one tire pressure and another with another. Just the tire to ground interface alone is enough to defy accurate calculations. The change in CRR is not directly related to the surface vibration as it is on a road bike. So many of the assumptions that will hold true on a road bike on varying pavement and even gravel can not be extrapolated to a fat bike. I would love to see this proven false but I am not at all hopeful. There are conditions where I ride my fat bike where the iBike could work, but those are more like a road situation than the use in snow conditions. It might even work on sand, since it will stay fairly constant, but I see no way to tell the computer that you are on sand vs gravel, vs pavement. if you solve that then I will be truly amazed. Let it be said i did not buy my ibike for fat biking. So I have no disappointment in that respect, however the more I think about fat biking the less I see how the ibike would work. I think this is the one place where a direct force might work and even then there are assumptions that have to hold true which might not be accurate. To me my fat bike is just a really fun thing to ride and I truly don't care that much about power. It might be cool to collect environmental info but my ibike does not collect accurate temperature ( I am not even certain if it a consistent bias/ offset)so it does not get used in the winter.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

I guess all of this boils down to what you're trying to accomplish.

If you're doing serious power training with your fat bike, trying to precisely hold power training zones while riding in snow, with wheels spinning, etc. then I agree this would be very challenging for PP (note this scenario might also cause problems for DFPMs as well). But I wonder...is it a good idea to get snow and slush all over those $1,000 power pedals or crank? And how good is their temperature compensation in super-cold conditions? :-)

Alternatively, if you're out having fun with your fat bike and trying to get an general idea of your power level, your efforts on winter hills, etc. then I think PP, with suitable parameters, would be useful to have on your ride.

What we're trying to determine now is recommended setup parameters for fat bikes.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

Velocomp wrote: ...if you're out having fun with your fat bike and trying to get an general idea of your power level, your efforts on winter hills, etc. then I think PP, with suitable parameters, would be useful to have on your ride.

What we're trying to determine now is recommended setup parameters for fat bikes.
Yes, this is exactly what I'm asking about. I don't share ronpei's pessimism and don't care to get wrapped up in fretting over the varied types of terrain that mountain/fatbikers encounter. This is a reality that we can't do much about. So, we may never be able to obtain pinpoint power accuracy under these admittedly difficult/varied ride surface conditions. But I'm still hopeful that getting "...a general idea of your power level" will be achievable. In my experience, this has not been achievable using CRRs appropriate and intended for road bikes.

By the way, my use of the term, "one-size fits all" clearly was a reference to using road bike CRRs across all bikes, not criticizing the fundamental role of Newton's Law in the iBike products. So, please, don't misconstrue my comments. As I said before, I'm happy that we've been able to agree on a needed area of investigation for better applicability of the iBike products to fatbikes. My only concern now is that this issue could be pushed to the very bottom of the list of many projects that I'm sure Velocomp is working on currently (which I totally acknowledge and respect) and that we find ourselves still lacking appropriate fatbike CRR values many months from now.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

In re-reading some of the recent posts, I want to add that, like me, many fatbikers are riding their bikes year-round -- not just in snowy conditions, or on the beach (where these bikes made their first appearance). So, to get corrected fatbike CRR values would benefit some of us all 12 months of the year, not just in the limited use case of snowy/slippery conditions. I would hope that the investigation of appropriate CRR values would not be limited to only the snow. In fact, I'd prefer good fatbike CRR values for the 150 rides per year that I do in "summer"/non-snow conditions, and, if need be, accept a little inaccuracy for the 10 or 15 rides per year I might do in snow here in New Jersey. I understand that the "summer" vs snow ratio might be different in other parts of the country. Thanks.
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Velocomp »

Ratman wrote:
Velocomp wrote: ...if you're out having fun with your fat bike and trying to get an general idea of your power level, your efforts on winter hills, etc. then I think PP, with suitable parameters, would be useful to have on your ride.

What we're trying to determine now is recommended setup parameters for fat bikes.
My only concern now is that this issue could be pushed to the very bottom of the list of many projects that I'm sure Velocomp is working on currently (which I totally acknowledge and respect) and that we find ourselves still lacking appropriate fatbike CRR values many months from now.
Actually, we expect to be doing some fat bike riding this week!
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Re: Anyone using PowerPod on a Fat Bike with any success?

Post by Ratman »

Velocomp wrote: Actually, we expect to be doing some fat bike riding this week!
Ah, being in Florida, the weather is unlikely to be a deterrent to riding. Riding the fatbike should be enjoyable, and perhaps it will yield some interesting new information. I wonder how the trails are in Florida? Have fun!
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