gtrob

I guess if it takes 2 people to run it anyway you might as well just hold him

Anyone have a design that can be used on flat without any assistance? Im sure I've seen one but no idea how it works

queerpunk

One of our track locals made a home-made one. It's pretty cool - it uses a clamp from a workstand to hold the bike by the seatpost. It's a manual-release via a string that releases the workstand clamp handle (thus releasing the bike).

It also is designed to tip over and be rolled off the track, which is nifty. IE, there are wheels on the face of the start gate that faces the infield. Once a rider is released, the operator tips the gate over, it lands on its wheels, and rolls off the track.

Quinn8it

I was lucky to be able to train a lot on the start gate at ADT a few years back.
One benefit of using the gate is being able to throw yourself out of it harder than from a holder, because it is so stable and doesn't allow your wheel to roll back as you start.

The real reason for training from a gate is learning how to precisely time your start with the countdown timer and the mechanical release that is connected to the timer. Jump a fraction early and the gate will hold you back and actually penalize you slightly.

I've not used one, but I can't imagine one of these DIY set ups actually recreating that key element..
Obviously I'm just guessing..
Seems to me you could practice the feeling of throwing yourself out of a gate with your rear wheel backed up against a block of wood that the holder steadied with his foot..

bungis

This might not be the case with power2max track as it doesn't auto-zero. It's manually zeroed by the user at the beginning of the ride or after changing rings. Couple other notes about this PM:

It's actually Rotor's road crankset with the following adjustments for track use:
- 144 BCD
- No auto-zero as mentioned
- Chainline

It uses a road BB and not Rotor's track BB, not sure if that's a big deal tho.

edit: I'm going to ask power2max about this specifically and report back here.

edit2: power2max said it was the low and high-frequency changing of RPM of a standing start that is the limitation. Hopefully they respond with specifics with the lower-bound RPM or typical time-frame before it transmits accurate readings.

edit3: 20 RPM and two crank rotations before it transmits data

slindell

Hold from the side and put a foot behind/under the tire to get something to push against. The foot also provides some feedback on how hard they are pushing back.

The ideal solo gate would have the countdown timer attached to the release then wheel itself off the track after the start - hopefully with a check to make sure the bike is not still attached.

carleton

Yeah, the foot under the rear wheel helps a lot. That's the next best thing to a proper starting gate.

carleton

Well, it's not an issue of auto-zeroing. I think it's more the fact that cadence and power are transmitted via the same transmission from the crankset. Actually it's more like cadence is calculated based on how often power is being transmitted via the single reed switch which also pulls double-duty as a cadence counter.

In order to calculate cadence, you need at least 2 readings. The cadence is calculated as 1/(time between the two readings).

Being that that power meter probably only has 1 reed switch, it will take about 2 pedal strokes to get enough of a sample to create a cadence.

The cadence value is used along with torque to calculate the power.

You can't have power till you have cadence. You can't have cadence till you get 2 transmissions from your reed switch. You can't have 2 transmissions from your reed switch till your pedal comes around between 1 and 2 complete rotations.

carleton

I could be wrong about power2max. I actually hope that I am. I like SRM, but $3,200 is a lot for a track power meter system these days.

The key to getting standing start data is equipping the crank with 2 reed switches so that the cadence can be calculated within 1 pedal stroke as opposed to two. That means you can calculate power within 1 pedal stroke.

Only the SRM offers 2 diametrically-opposed reed switches as an option. And within SRM, only the wired SRM V head unit has firmware that has options to read data from 2 reed switches.

I had maybe the only wireless SRM cranks with 2 reed switches. No wireless head unit (including SRM or Garmin) could read the data properly. My cadences (and therefore, power) were all doubled.

Quinn8it

This is one of those topics where Carleton and I are on opposite ends of the spectrum..

As a a weekend hack masters racer not only do I not really have any need for .5-second sample power data- I don't really need anything shorter than 10-second.. 10"/30"/60" are the metrics that appear to affect my race day performance and unlike your first stroke in a standing start or your 1/2 second peak power- they are actually trainable..

Edit:
to be clear- like anything else, I agree more is better, I just don't think that the lower sample rate or delay is a reason to totally write off every power meter except SRM..
At this point I have 4 power meters including an old wired SRM, and still have less invested than a new SRM-Track cost.

carleton

Would you agree that they should all be cheaper?

Quinn8it

Totally!

slindell

In theory the stages and power2max can get 2 readings per revolution since they use accelerometers instead of magnets to pick up the cadence. Powertap kicks in sooner than a road srm and seemed to work ok on the track for starts with reading starting at 3-5mph.
If it is just the number of reed switches you could increase the resolution of a srm by putting 2 magnets 180 degrees apart to get it to read twice as fast. The cadence and power numbers would be ego inflating until you post processed to divide by 2 unless you have a head unit that supports 2 reed switches. I have done this with speedometer magnets and reduced the programmed wheel size in half to get more stable readings at slower speeds.

gl98115

I can't wait for a track version of the Pioneer power meter

Power Meter | Pioneer Electronics USA

carleton

This is crazy. Using an accelormeter to calculate anything other than acceleration is absurd.

Power tap measures torque furthest away from where the power is input (the foot). Think of all of the vaiables between the foot and rear hub:
shoe --> cleat --> pedal --> crank arm --> chainring spider --> chainring --> chain --> rear cog --> rear hub.

SRM, Quark etc measure here:
shoe --> cleat--> pedal --> crank arm --> chainring spider

This is why pedal or cleat based systems could be more accurate because there is less between the source and the power meter.

I think Powertap is OK for road/TT stuff. But, not so much for track. That's just my opinion.

The only head unit on the market that can read from 2 reed switches is the Powercontrol V (and maybe VI, not sure). But post processing manually is a real pain.

carleton

It looks like the Pioneer is a mix of the Quarq and Stages power meters. Where it measures strain guages on the crank spider and the non-driveside arm.

Do they have plans to make a track version?

wens

Eh, velocity is just the integral of acceleration. Depending on sampling frequency calculating from the secant of acceleration and measured torque could very well be more accurate than averaging torque over each revolution. There's some calculation error either way, so my preference would probably depend on how well the method is executed more than the method.

gl98115

The Pioneer has strain gauges on both crank arms. The pod in the chain rings is the transmitter. They use magnets on both sides, so twice as much cadence data. But not quite sure how they get 12 data points per revolution accurately.

I haven't read that they are working on a track version, but haven't asked either.

carleton

Thanks for the correction.

Yeah, I couldn't figure out how they get "12 data points" either. I suspect that that is marketing hype.

gl98115

Here are the details in patentese for one such device.

Patent EP2433097A1 - Sensor apparatus and method for determining pedalling cadence and travelling ... - Google Patents

Tman1965

True, true, but the only thing that propels you forward are the forces at your rear wheel. It might be good for one's ego to know that you have 10 watts more at the pedals but they are not going to move you forward if they end up in the drive train.
Having said that I would love to have a FES pedal force measuring system: measuring rate 200Hz

carleton

That sounds dreamy!

Bulldogsprinter

Found this article yesterday SRM Torque Analysis of Standing Starts in Track Cycling (P85) - Springer . SRMs torque analysis on a track bike, records torque at 200hz, whole point is seeing your standing starts. That would be some serious analysis, probably wouldn't make any faster though....

bungis

Speaking of power meters, can anyone with Dura-Ace FC-7710 cranks do the community a huge favor and measure the width of the interior surface of both crank arms at roughly the center of the crank? It would be to fit a 4iiii Precision which currently requires a 24mm wide surface.

Diagram:

Shotland

my friend has those. I'll ask him to do it. You want to know the width of the flat part?

bungis

Yes, the width of the flat part thanks. I think it'll be close to 24mm!