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Post by Rowan on Jul 24, 2020 10:39:06 GMT
Excellent news! Well done.
The Ah reading is a measure of current over time. If you use the app with the 'lanch' button, it resets the Ah count at race start and lets you know how many ampHours you've used through the race. If you have a good idea of your batteries capacity it can give a good indication of how much power you have left.
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ben
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Post by ben on Jul 24, 2020 13:36:29 GMT
Ahh yes I see that now thank you! Just been for our first test run today with some what success. All of the telemetry is working like a dream thanks!
Ben
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Post by keduro on Jul 24, 2020 14:38:13 GMT
Good news Ben, great to hear all now working. Fwiw our experience is that we get about 28Ah from each battery before the voltage falls off a cliff. Although the batteries are specified as 32Ah this is achieved discharging over 20 hours. Discharging over shorter periods, e.g. 90 mins, results in a reduced energy output. We generally aim to run our cars at an average current of between 17A and 19A.
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ben
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Post by ben on Jul 24, 2020 17:18:08 GMT
That makes sense. That average, i assume that is when on long straights going a steady speed. Does the current that it pulls vary when setting off? And by how much if it does. I only ask as when we accelerate from 0 our amps fly up and have tripped out our 80 amp breaker a couple of times. I must admit that the surface we set of on was slightly up hill and not the smoothest so I’m not sure if that was the reason. Also what gear ratio are you using or is it just a stock kit car sprocket? We were using a 2.15 however we could change this for a larger ratio if this is the problem. Sorry for the amount of questions😬
Thanks Ben
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Post by keduro on Jul 24, 2020 19:11:15 GMT
That makes sense. That average, i assume that is when on long straights going a steady speed. Does the current that it pulls vary when setting off? And by how much if it does. I only ask as when we accelerate from 0 our amps fly up and have tripped out our 80 amp breaker a couple of times. I must admit that the surface we set of on was slightly up hill and not the smoothest so I’m not sure if that was the reason. Also what gear ratio are you using or is it just a stock kit car sprocket? We were using a 2.15 however we could change this for a larger ratio if this is the problem. Sorry for the amount of questions😬 Thanks Ben Hi Ben .... well actually once we get up to a steady speed on long straights the current drops way down as the motor reaches its optimal RPM - in our experience ~1900 RPM for the older motors, and ~2100 RPM for the newer motors. Accelerating out of corners draws higher currents and you really need to look at the overall average. Our Banchory Greenpower telemetry averages various values including current over each lap and also over every 15s and we get a plot of the averages. You can build your own telemetry displays from the dweet data - freeboard (from dweet.io) allows you to build dashboards which are free for a trial period, or you can use Node-Red as outlined in the eChook documentation, or you may be able to use the eChook live data (you'd need to check with Rowan the current operational status :-) ). We started off using dweet and freeboard but found we wanted more than freeboard could offer (and we didn't want to pay for it (we're Scottish!!)), so we build our own telemetry system. What I'd recommend though is downloading the eChook log file from the phone. The log file records the data values every 250ms. The data is in CSV format and can be opened directly in Excel where you can then average the data, plot charts, and so on. This will give you a much better view of average current and the like. From a standing start our telemetry often shows a current value of 100A+ for very short periods of time. Not sure how we measure that as the current sensor is only calibrated to 50A. Luckily the period for which that current is drawn is only a fraction of a second, and has never caused our 70A cutout to trip. Gearing - ah, there's no simple answer to that! We have only raced on three different circuits, viz: Alford which is a 1/4 mile oval with very tight 180 degree bends, East Fortune which is 1.14 miles circuit with mostly sweeping bends but a grotty track surface through the pit straight, and Silverstone which was a 1.64 mile circuit with sweeping bends and long straights. Each of the three circuits required different gearing on our original car. The car is a custom build and has the standard 20" wheels - 1.429m circumference with the tyres we are using. Our driven 'chainring' has 72 teeth. At Alford we used a 14 tooth sprocket (we placed 1st in both races). At East Fortune we used a 15 tooth sprocket (we placed 1st and 2nd in the two races). At Silverstone, after the practice session we decided on a 16 tooth sprocket which we used for the qualifier race. We finished 26th in the qualifier, but (big but), if the qualifier had not been cut a little short to allow the event to get back on schedule, then its most likely we would have run out of battery before the 90 mins were up. We reverted to a 15 tooth sprocket for the final and finished 27th, and had a bit of battery power left. If using a fixed gear ratio (i.e. no gears to shift) then selecting the optimal gear is I'd say the key challenge to performing well in the greenpower events. Select too low a gear and the car runs slowly and you finish with batter power to spare. Select too high a gear and the car runs much faster, but you may run out of battery power before the end of the 90 mins. Undoubtedly though telemetry gives you a huge insight into how your car is performing. Before we had telemetry on our original car, the only test was to put the batteries in and see if we could last 90 minutes. Not very scientific and not time efficient either. For 2020 we have added a new custom built car. Before Covid came along we managed two track test sessions on the 1/4 mile Alford track. First session we had no telemetry (didn't get it finished in time). The second session we know the car was out performing our original car, but the current draw was averaging ~25A average. Not sustainable. We know we need to work on the gearing and are eagerly awaiting a loosening up of restrictions up here so that we can get the car on the track again. Hope this helps. Happy to answer questions.
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ben
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Post by ben on Jul 24, 2020 20:10:34 GMT
So you think we shouldn’t worry about the data provided for direct input on the phone and find a way to create an average of the data? We still have a bit of trouble downloading data onto excel so once we figure that out we can find averages. Yes we have looked at the Dweet dashboards and they look very good, are you saying we can change individual panel to show an average data instead of inputs every 250milisecs?
It’s interesting that your read outs say you are pulling 100A+ and not breaking as when our 80A breaker goes it cuts off the telemetry and the final reading on the readout is 80-85A so quite sensitive. From your experience do you pull close to 70A coming out of corners coming out of the hairpin at Alford for example? Or does the speed and momentum mean you don’t need as much torque?
As for the gearing we have 3 options for the frount- 11,12 and 13 and we have a full 11-34 tooth sprocket set on the back. So after hearing you have a 72 tooth sprocket is daunting and may be the cause of our lack of torque and the solution to our problems. As your ratio is 5.1 when using the 14 tooth on the driving side. And 4.5 when using the 16 tooth where you would have run out of battery? That means that if we have the same trend we will run out of battery very quickly.
I am not sure how much you know about the F24+ catagory but the race is only 60mins do you know if many people have an issue with running out of battery or is it usually mechanical issues that cause people to stop?
Also did you just go down to the local race track to do your practice runs or were the practice results else where?
Im not sure if this would help visualise but there is lots on pics on the instagram that could help see if we are doing things right😂 -tad_e_greenpower Thanks, Ben
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Post by keduro on Jul 25, 2020 10:47:08 GMT
So you think we shouldn’t worry about the data provided for direct input on the phone and find a way to create an average of the data? We still have a bit of trouble downloading data onto excel so once we figure that out we can find averages. Yes we have looked at the Dweet dashboards and they look very good, are you saying we can change individual panel to show an average data instead of inputs every 250milisecs? It’s interesting that your read outs say you are pulling 100A+ and not breaking as when our 80A breaker goes it cuts off the telemetry and the final reading on the readout is 80-85A so quite sensitive. From your experience do you pull close to 70A coming out of corners coming out of the hairpin at Alford for example? Or does the speed and momentum mean you don’t need as much torque? As for the gearing we have 3 options for the frount- 11,12 and 13 and we have a full 11-34 tooth sprocket set on the back. So after hearing you have a 72 tooth sprocket is daunting and may be the cause of our lack of torque and the solution to our problems. As your ratio is 5.1 when using the 14 tooth on the driving side. And 4.5 when using the 16 tooth where you would have run out of battery? That means that if we have the same trend we will run out of battery very quickly. I am not sure how much you know about the F24+ catagory but the race is only 60mins do you know if many people have an issue with running out of battery or is it usually mechanical issues that cause people to stop? Also did you just go down to the local race track to do your practice runs or were the practice results else where? Im not sure if this would help visualise but there is lots on pics on the instagram that could help see if we are doing things right😂 -tad_e_greenpower Thanks, Ben Morning Ben .... Mmm, I would suggest you do need to look at your gearing . I hadn't realised that you were building for F24+ but I think the basic objective remains the same, i.e. run the motor as hard as you can to maximise speed and distance covered, such that when you finish the 60 minute race your batteries are exhausted (but not to the point of damaging the batteries which is possible if the voltage drops below around 10 to 10.5V for a sustained period). Have you looked at the motor performance curves as part of determining your gearing? I attach two documents - the pdf is the performance curves for the older Fracmo motor that was supplied by Greenpower prior to last year, and the xls is performance curves for the motor currently being supplied by Greenpower. I'll assume you are using one of the new motors. For F24 we aim to run the motor at its most efficient, i.e. around 2100 RPM at around 17A. As you can see in the graphs though, this is not the point of maximum output power - this occurs at around 1200 RPM and 57A !! Pull 57A on average and you will certainly not manage 60 minutes from a 32Ah pair of batteries. For F24+ I'd suggest the following as a starting approach. Estimate what average current is sustainable for 60 minutes. In F24+ we can sustain 17A to 18A for 90 minutes, so it might be reasonable to assume you could sustain 25A or 26A for 60 minutes. Looking at the data table, 25A would flow at around 1890 RPM. Then determine your target speed, let's say 30 mph (the fastest F24+ cars go a bit faster than this). 30 mph is 13.4 m/s. If your wheel circumference is say 1.4m (that's what ours is for our 20" wheel and tyre combination) then 13.4 m/s ground speed means the axle rotates ( 13.4 / 1.4 ) revolutions per second, = 9.6, which is 576 RPM. With the motor @ 1890 RPM and the axle @ 576 RPM you would need gearing of 1890 / 576 ~= 3.3. If you had say a 13 tooth sprocket on the motor then you'd be looking at 43 tooth ring on the axle. If it were me though, I'd go for a bigger ring on the axle to give you a greater range of possible sprockets to try on the motor as 13 teeth is towards the lower end of what's available. Maybe 16 tooth sprocket on motor and 52 tooth ring (readily available) on axle. Your actual numbers will vary depending on your wheel size but hopefully this helps determine the gearing to start with. Theory is fine, but this doesn't in any way substitute for testing on the track with various different sized sprockets and using the telemetry to monitor the impact. Re other points ... "we shouldn’t worry about the data provided for direct input on the phone" - an interesting one. For our team we don't display any data to the drivers, other than the total battery voltage. In F24 the drivers are younger and the question is would they drive any differently if they knew the instantaneous current flow, or the total Ah so far. Our drivers are tasked with driving as fast as they can, i.e. max throttle, brake only if necessary, avoid other cars, and protect the car. For older drivers in F24+ it may be different and they may use the phone as a data dashboard and modify their driving accordingly. I recall having exactly this conversation when I first met Rowan at Silverstone. The eChook app was developed in an F24+ context hence the potential to use it as a dashboard. "... your read outs say you are pulling 100A+ and not breaking as when our 80A breaker goes it cuts off the telemetry and the final reading on the readout is 80-85A so quite sensitive" - we use this this kind of breaker and it seems to cope with the very brief current spikes. We also have a separate fused 24V supply to our telemetry so that it continues to run when the main power is off or should the breaker operates. "From your experience do you pull close to 70A coming out of corners coming out of the hairpin at Alford for example? Or does the speed and momentum mean you don’t need as much torque?" - from our logs of racing at Alford we typically pull around 30A to 40A max coming out of the tight corners. For F24+ "do you know if many people have an issue with running out of battery or is it usually mechanical issues that cause people to stop" - can't answer that I'm afraid. There were F24+ cars at both East Fortune and Silverstone but guess we weren't looking too closely . "Also did you just go down to the local race track to do your practice runs or were the practice results else where" - our local race track is Alford, but that is 20 miles away. That's where we have done almost all of our testing - we tried two other "circuits" but they were either too rough or had right angled bends!. Sadly we don't have the luxury of being able to run the cars at Banchory Academy where the team is based. What's really important though is to make good use of the practice session at the Greenpower events before the actual races. Try different sprockets / gearing, monitor the telemetry, determine what gearing is likely to work best. If you have the ability to shift gears (? - you did say you have "11 - 34 on the back") then making a single gear choice is not so critical, but still important in informing the drivers which gear to target driving in. " there is lots on pics on the instagram" - 'fraid I'm not an instagrammer (nor facebooker), its an age thing! I think I've hit most of your points. Good luck with the gearing in particular. BTW, out of curiosity, which team are you, where are you based - I'll look out for you should we be at the any event at the same time in future. Cheers ..........
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Post by keduro on Jul 25, 2020 11:01:16 GMT
Ben .... just pulled summary plot from our race day at Alford last year ... see below. You can see there that our current (albeit clipped) didn't get over 40A very often and most of the time averaged around 18A. But yes, we did have a problem with higher currents during the first leg of race 2 - we pulled in the driver at the earliest opportunity, i.e. after 15 minutes for F24, and found we had warm brakes. Something had been binding. A good thump fixed it and we got the car out again pretty quickly. This was another great example of the benefits of telemetry. We saw the problem early in the data and took action.
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ben
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Post by ben on Jul 26, 2020 9:43:39 GMT
Morning
That is interesting to note that we should be pulling around 25 amps to sustain for the hour. Also thank you for those motor performance curves may I ask, do you have an active graph chart updating consistantly throughout the race that that you can see in the pits or did you know just due to the higher average current on the telemetry you had?
Once I get back to the car tomorrow I will do the calculations with that formula you gave me to see the gear ratio we should be aiming for. I feel like this will only be defined through going to a race day or a test track like you said. At the moment I feel like we have a way too small ratio😂.
We are using the mobile as a dashboard however as you say I’m am unsure if we will use it too much to alter the way we drive with was just a good concept in the design stage of the build.
We may go for this type of breaker That you linked after we change the gear ratio as it will most likely be the gearing that will need to be changed to sort the amperage under control
Our team name is ‘Tad E’ we are based in Tadcaster looking at the races coming up we have our fingers crossed that aintree, Liverpool will be not cancelled closer to the time as this is only a couple hours away. In the mean time we may see if we can get down to Croft to do some testing.
Thanks, Ben
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Post by keduro on Jul 26, 2020 11:11:04 GMT
Morning That is interesting to note that we should be pulling around 25 amps to sustain for the hour. Also thank you for those motor performance curves may I ask, do you have an active graph chart updating consistantly throughout the race that that you can see in the pits or did you know just due to the higher average current on the telemetry you had? Once I get back to the car tomorrow I will do the calculations with that formula you gave me to see the gear ratio we should be aiming for. I feel like this will only be defined through going to a race day or a test track like you said. At the moment I feel like we have a way too small ratio😂. We are using the mobile as a dashboard however as you say I’m am unsure if we will use it too much to alter the way we drive with was just a good concept in the design stage of the build. We may go for this type of breaker That you linked after we change the gear ratio as it will most likely be the gearing that will need to be changed to sort the amperage under control Our team name is ‘Tad E’ we are based in Tadcaster looking at the races coming up we have our fingers crossed that aintree, Liverpool will be not cancelled closer to the time as this is only a couple hours away. In the mean time we may see if we can get down to Croft to do some testing. Thanks, Ben Good morning Ben, We have built our own telemetry web pages that allow us to see the near live values from the car, and a constantly upgrading graph. Here are a couple of screenshots: (note that this is simulated data, not read data) At the Alford race we were able to look at both the near live values of current and the average current on the chart and that's what informed our decision to pit the car as the current was too high. The graph I included a couple of posts back was generated from the data downloaded from the phone in the car. Being every 250ms the data has more detail than what we see on the telemetry web site pages which only get new data every 1500ms. As mentioned earlier too Rowan and the eChook guys also have a telemetry live data site that teams can use - you'd need to check with Rowan though what the current status is as I know he has been working on it.s Re your current gear ratios .... with what you have currently fitted to your car, it is worth trying 11T on the motor and 34T on the back as that gives you a ratio of 3.1. Worth also checking using other ratios, but my gut feel would be that you will struggle with getting a current that could be maintained for 60 mins. And yes, track tests are a must in my opinion . Ah, so you are in North Yorkshire! We had considered coming down to race at Croft before it was cancelled as it is the most northerly race in England and the closest race for us outside of Scotland. Sadly I think you will be disappointed - Aintree has been showing as cancelled for some time now on the the Greenpower site. The only two races scheduled to be held are Castle Combe on 13th September and Goodwood on 11th October. Also unfortunate for yourselves, both those races are full for F24+. Let's know how your gearing goes .....
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ben
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Post by ben on Jul 26, 2020 20:21:46 GMT
Good evening,
I see so you have developed your telemetry to suit your needs and can edit it to how you want any time. That’s quite sophisticated, how hard was it to create this telemetry? Was there much coding and knowledge on your part or was it based off of other telemetry systems such as Rowans eChook telemetry or a website to help? Also (not taking away from the current telemetry) what was ‘wrong’ or different to make you want to create your own telemetry?
Indeed we need to machine one more part for the motor shaft and we can fit the 11 tooth sprocket on so I will let you know how it runs with a 1:3 ratio.
Indeed we are disappointed about Aintree. You mention there is a maximum amount of people that can attend the races. is that in normal circumstances I.e. we will need to be quick to enter? or is that just down to the current circumstances? We were not looking to go that far south for our fist race anyway which is ok. Yes Croft is one of the closes races to us so will be a go to for definite will hopefully get to meet you and your team there!
Thanks, Ben
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Post by keduro on Jul 26, 2020 21:06:58 GMT
Good evening, I see so you have developed your telemetry to suit your needs and can edit it to how you want any time. That’s quite sophisticated, how hard was it to create this telemetry? Was there much coding and knowledge on your part or was it based off of other telemetry systems such as Rowans eChook telemetry or a website to help? Also (not taking away from the current telemetry) what was ‘wrong’ or different to make you want to create your own telemetry? Indeed we need to machine one more part for the motor shaft and we can fit the 11 tooth sprocket on so I will let you know how it runs with a 1:3 ratio. Indeed we are disappointed about Aintree. You mention there is a maximum amount of people that can attend the races. is that in normal circumstances I.e. we will need to be quick to enter? or is that just down to the current circumstances? We were not looking to go that far south for our fist race anyway which is ok. Yes Croft is one of the closes races to us so will be a go to for definite will hopefully get to meet you and your team there! Thanks, Ben Evening Ben. The initial version of our telemetry was not too involved, basically we used the dweet data to update a few gauges on a single page, first using freeboard then using a web server I have access to. Since then it has become a bit more sophisticated. First we added the running charts, then a map display of the car's GPS position on the circuit, then some other features, for example, based on battery energy consumed we make an estimation of how long we think the batteries will last (good for raising stress levels in the pits). There is a fairly significant coding effort involved. In our case it is implemented as a number of ASP.net Core pages, plus quite a bit of javascript / css / html for the dynamic updating of the pages. You'd probably need someone with a reasonable understanding of building web apps. Our telemetry pages were built from scratch. When we started off I had not seen Rowan's eChook Live Data pages. Rather poor excuse on my part .... on the www.echook.uk/ page there are two links to "Live Data" - one in the middle of the page next to Hardware and Android App, and one on the top menu bar next to Documentation and Forum. The first of those takes you to dweet.io, and I had assumed that the other would do the same, I had never clicked on it to find that the eChook guys had built telemetry web pages. It was only after we had build our own pages using the dweet data that I discovered the eChook Live Data pages. Having gotten that far we continued with our own development as we wanted to add a couple of things that the eChook Live Data didn't include. That said, the eChook Live Data is a great resource and gives huge benefit in being able to remotely monitor what the car is doing in near real time. Need to check with Rowan though the current status - as mentioned I know he has been working on it, and right now, clicking on the link gives a "504 Gateway Time-out" error. Will be most interesting to see how you get on with the 1:3 ratio. I don't normally get involved in race entries, one of our other mentors takes care of that. I do believe that even in normal times the number of entries for any event are limited, presumably dependent on the circuit capacity, pits space, etc. Cheers ... Keith
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Post by Rowan on Jul 26, 2020 22:06:59 GMT
Wow, I go on holiday for a few days and the quality of discussion on here skyrockets! I should go on holiday more often Keith's development of the telemetry is excellent, and to be fair, more advanced than anything we had planned with our own site. The eChook live data site needs a beta version of the app to use that a few teams have, however I then started on a completely new version which is fighting for time with too many other projects. It's getting there slowly! As Keith just pointed out, looks like my server has gone down at the moment... I'll check on it when I get home!
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ben
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Post by ben on Jul 27, 2020 8:05:52 GMT
Morning Keith, Well I guess it was a happy mistake that you did not see rowans eChook code as now you have your own. I think for us we will stay with this code for the foreseeable future as it seems to do everything that we need it to do for now. And it was easy enough to figure out how it works also.
I see I will keep an eye out for the amount of entries at the events to make sure we go to all the ones we would like to. It makes sense to limit entries to the amount of pit space they have though.
Cheers for your help, Ben
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