how to work out what speed i am going on a turbo

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ricky1980
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how to work out what speed i am going on a turbo

Postby ricky1980 » Thu Oct 25, 2012 21:21 pm

just got a turbo and wondering how to extrapolate speed and then work out my wattage output from the linear charts.

is it magnets to the rear wheels to count RPM and then work back based on gearing?
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amaferanga
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Re: how to work out what speed i am going on a turbo

Postby amaferanga » Fri Oct 26, 2012 07:59 am

Linear charts?

You'll need any computer with a rear wheel mounted speed sensor to get speed, but any Wattage estimate is likely to be wrong.
More problems but still living....

bobones
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Re: how to work out what speed i am going on a turbo

Postby bobones » Fri Oct 26, 2012 11:10 am

ricky1980 wrote:just got a turbo and wondering how to extrapolate speed and then work out my wattage output from the linear charts.

is it magnets to the rear wheels to count RPM and then work back based on gearing?

You just need a speedo that runs from the back wheel. You want one that has an average speed function so you can easily get your average speed over a set time. Of course you can work out your average speed just using distance/time. Cadence is also useful for doing workouts on the turbo, but you don't need it to estimate power.

I am using my Garmin 500 for this and it's perfect. You program a workout into it with the intervals you want to do and it creates a new lap for each interval period. Once you upload it to Garmin Connect you can easily see your average speed for a lap.

For example, this morning I did a T8 + T8 FTP test, which is 10 minutes warm-up followed by an 8 minute time trial, 5 minutes recovery and another 8 minute time trial. The T8 sections are done at hard effort, i.e. threshold level. Here's the workout intervals as defined on Garmin Connect.
Image

The resulting workout is here http://connect.garmin.com/activity/237136108

As you can see from the lap splits, my average speed over the 8 minute sections was 19.2mph or 31km/h which, according to the power chart for the Tacx Satori, corresponds to around 243w at resistance level 5. Taking 90% of that for the T8 test gives an FTP estimate of 219w.

Now I know this could be wildly inaccurate, but it seems to be in the ballpark for me, and it is at least a baseline I can use to measure any performance gains assuming I set up the turbo in the same way with respect to tyre and roller pressure.

If you don't have a Garmin with a speed/cadence sensor then just use your speedo to get your average speed over the set time of the test to work out your power.

Here are a couple of images of a spreadsheet I created to convert speed to power for the Taxc Satori. I first worked out the slope and intercept from 2 points on the graph for each level and then converted to mph.
Image

Image

Edit: I see you bought an Elite trainer so you would need to find the equivalent power curve information for your model as this stuff only applies to the Tacx Satori.

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PeteMadoc
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Re: how to work out what speed i am going on a turbo

Postby PeteMadoc » Fri Oct 26, 2012 15:09 pm

WTF?????

Sorry but speed on a turbo means NOTHING! Unless you have some fancy calibration thing like bobones above.

If you have some kind of power meter then great, if not use your HR.

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Pross
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Re: how to work out what speed i am going on a turbo

Postby Pross » Fri Oct 26, 2012 15:56 pm

PeteMadoc wrote:WTF?????

Sorry but speed on a turbo means NOTHING! Unless you have some fancy calibration thing like bobones above.

If you have some kind of power meter then great, if not use your HR.


Not strictly true. If you are riding at '20mph' on a turbo then you are working harder than you would be at '15mph' on the same setting.

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PeteMadoc
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Re: how to work out what speed i am going on a turbo

Postby PeteMadoc » Fri Oct 26, 2012 16:16 pm

Pross wrote:
PeteMadoc wrote:WTF?????

Sorry but speed on a turbo means NOTHING! Unless you have some fancy calibration thing like bobones above.

If you have some kind of power meter then great, if not use your HR.


Not strictly true. If you are riding at '20mph' on a turbo then you are working harder than you would be at '15mph' on the same setting.


Well yes that is true

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JGSI
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Re: how to work out what speed i am going on a turbo

Postby JGSI » Fri Oct 26, 2012 16:28 pm

PeteMadoc wrote:WTF?????

Sorry but speed on a turbo means NOTHING! Unless you have some fancy calibration thing like bobones above.

If you have some kind of power meter then great, if not use your HR.



You sound like the same 'grumpy' age bracket as me...
but honest there are more ways to 'skin a cat' when it comes to to using the turbo as a training aid. the Op has every right to ask.

ricky1980
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Re: how to work out what speed i am going on a turbo

Postby ricky1980 » Fri Oct 26, 2012 23:50 pm

i think atm the key for me is to get a HRM and then see my zone first...i am on the road every day so i suppose i can compare my effort with the speed of the cars :) i think it is more important for me to get to know my fitness first and come up with a regime for training?
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bahzob
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Re: how to work out what speed i am going on a turbo

Postby bahzob » Sun Oct 28, 2012 11:46 am

JGSI wrote:
PeteMadoc wrote:WTF?????

Sorry but speed on a turbo means NOTHING! Unless you have some fancy calibration thing like bobones above.

If you have some kind of power meter then great, if not use your HR.



Sorry but are just wrong. Provided you exercise some consistency in terms of set-up and have a bit of common sense speed is a better measure than HR for indoor workouts, pretty much for the same reason power is better.
- It measures an output not an input.
- It responds instantly to increased intensity (and this is becomes more important as intensity increases. Turbo sessions will typically be of higher intensity so this is more of an issue.)
- It is less dependent on external factors

It doesn't require anything complicated to use. Just a rear wheel speed sensor. You can conduct a ramp test using speed as a variable rather than power and end up with speed based zones that will serve as an adequate substitute for power zones for turbo training.

I have a turbo, rollers and a power meter so I can make an informed comparison as the chart below shows. (all points are average power and speed for the interval concerned)

The red dots are points on my warm up (220W>380W in 20W increments every minute)

The yellow dots are the work (250W, 300W, 350W) and recovery (200W) intervals (work intervals varied from 5>15 minutes duration and recovery were all 5 minutes.

Image

It's pretty clear that the relationship is linear and speed is a good indicator of power and this relationship is independent of interval duration.

It also shows that you could do a ramp test based on speed and use the results to estimate speed based zones that would be similar to those resulting from a power test.

The second chart shows the same data but with HR vs Power.
Image
It clearly demonstrates the big issues with HR, it lags actual intensity and varies according to interval duration.

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Alex_Simmons/RST
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Re: how to work out what speed i am going on a turbo

Postby Alex_Simmons/RST » Sun Oct 28, 2012 20:15 pm

bahzob wrote:It's pretty clear that the relationship is linear and speed is a good indicator of power and this relationship is independent of interval duration.

It also shows that you could do a ramp test based on speed and use the results to estimate speed based zones that would be similar to those resulting from a power test.

That might be the case on your trainer and is a useful method on trainers where this is repeatable and have the characteristics your trainer does, however not all trainers, even if you set them up exactly the same (which is not so easy), are able to be consistent in their power-speed relationship from session to session, let alone during a session, nor are all of them linear in their power-speed relationship.

Out of interest, what's the slope of your trainer? How many W per km/h.

bahzob
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Re: how to work out what speed i am going on a turbo

Postby bahzob » Mon Oct 29, 2012 11:22 am

Alex_Simmons/RST wrote:
bahzob wrote:It's pretty clear that the relationship is linear and speed is a good indicator of power and this relationship is independent of interval duration.

It also shows that you could do a ramp test based on speed and use the results to estimate speed based zones that would be similar to those resulting from a power test.

That might be the case on your trainer and is a useful method on trainers where this is repeatable and have the characteristics your trainer does, however not all trainers, even if you set them up exactly the same (which is not so easy), are able to be consistent in their power-speed relationship from session to session, let alone during a session, nor are all of them linear in their power-speed relationship.

Out of interest, what's the slope of your trainer? How many W per km/h.


Yes I know, my post was in reaction to the view that speed tells you "NOTHING".

IMO its better for indoor work than just HR though ideally you use them together in conjunction with RPE if you don't have a power meter. It's just daft to pay no attention to it whatsoever especially if used with a bit of common sense it can help with executing training and measuring progress.

In practice I think it's not too difficult to get round the setup problems with a turbo, even less so with rollers which have fewer variables.

It helps if you have a standard ramp to max routine just increasing speed by a small amount every minute for 8-12 minutes. (I use same one for both max tests and warmup, warmup I just duck out a couple of minutes before what I can do on max). After a few sessions you soon get used to how the effort ramps with speed and if there are any problems with setup can sort it out. HR can help with this as well. (as often as not if I have an issue its to do with being too hot and HR playing up as a result, so "fix" is nothing to do with turbo, rather shedding some clothing and turning up the fan).

As for slope at 10.5W/km/h (it varies for very low watts but thats not an issue as no testing/training takes place at that intensity).

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Alex_Simmons/RST
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Re: how to work out what speed i am going on a turbo

Postby Alex_Simmons/RST » Mon Oct 29, 2012 20:45 pm

bahzob wrote:
Alex_Simmons/RST wrote:
bahzob wrote:It's pretty clear that the relationship is linear and speed is a good indicator of power and this relationship is independent of interval duration.

It also shows that you could do a ramp test based on speed and use the results to estimate speed based zones that would be similar to those resulting from a power test.

That might be the case on your trainer and is a useful method on trainers where this is repeatable and have the characteristics your trainer does, however not all trainers, even if you set them up exactly the same (which is not so easy), are able to be consistent in their power-speed relationship from session to session, let alone during a session, nor are all of them linear in their power-speed relationship.

Out of interest, what's the slope of your trainer? How many W per km/h.


Yes I know, my post was in reaction to the view that speed tells you "NOTHING".

IMO its better for indoor work than just HR though ideally you use them together in conjunction with RPE if you don't have a power meter. It's just daft to pay no attention to it whatsoever especially if used with a bit of common sense it can help with executing training and measuring progress.

In practice I think it's not too difficult to get round the setup problems with a turbo, even less so with rollers which have fewer variables.

It helps if you have a standard ramp to max routine just increasing speed by a small amount every minute for 8-12 minutes. (I use same one for both max tests and warmup, warmup I just duck out a couple of minutes before what I can do on max). After a few sessions you soon get used to how the effort ramps with speed and if there are any problems with setup can sort it out. HR can help with this as well. (as often as not if I have an issue its to do with being too hot and HR playing up as a result, so "fix" is nothing to do with turbo, rather shedding some clothing and turning up the fan).

As for slope at 10.5W/km/h (it varies for very low watts but thats not an issue as no testing/training takes place at that intensity).

Cool, thanks.


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