Personal Projects

[the_termin8r]

Quick update:

I’ve updated Banshee’s page on the site and will make a Mod V8 Pics tab when my parts come in.

This is the new system diagram:

A hell of a lot less wires and they’ll look like even less in person as most of them are packed in the receiver box and the casing that the programmer will be in. Wire lengths are back to normal and hence I haven’t measured them.

The total weight of the car (fully loaded with a battery and camera) has gone down from 2642g to 2500g. It weighs 2500g when it’s running slightly heavier tyres and a slightly heavier battery. Goes go who just how heavy the extra stuff was.

[the_termin8r]

The parts I was waiting for came in earlier today. Despite it being a fairly simple design, it was a bit of pain to route all the wires inside the box, but I got them packed in eventually and everything works. I’m still a bit annoyed that I couldn’t get a DPST with a missile hatch in 6mm (they only came in 12mm). Now I can get the telemetry data and reprogram the ESC by just plugging in a USB cable as opposed to opening the receiver box every time.

The next order of business is to find a dust cover for the USB port (I’m currently using a piece of fake carbon fibre sticker) and to go for a couple of baseline runs on 3S, then it’ll be time for 4S. Stay tuned for a PRR soon.

[lpfan61]

Can’t wait to see it on the road!

[the_termin8r]

The last run was almost 3 months ago. In 3 days it will be exactly 3 months if I haven’t gone for a run in that time.

[the_termin8r]

Banshee PRR:

Baseline run 1:

Went for a run for the first time in 3 months earlier today. The purpose of this run was to get baseline results on the telemetry for 3S running, this is so that I can get a rough idea of how it might perform when I come to run the new 4S battery.

Conditions weren’t great, the ground was moist which was bad news, because for these slicks to grip properly, it either needs to be chucking it down with rain or it needs to be bone dry. And as I’ve come to realise, the current tyres are over a year old, so I will change to new ones for the 4S run.

In terms of performance, the truck was solid as usual. There were only a couple of differences that I felt between running the sensorless Sidewinder 3 and the new sensored Mamba X. The first is the initial throttle feel, with the MX I can squeeze the trigger very slightly and the truck will crawl very slowly, whereas with the S3 I’d squeeze it and it would take off at a few miles an hour (~ 6-7). The second is the initial acceleration, it feels like I have more low-down torque because I can pop a wheelie with a short squeeze (trigger travel-wise, not duration-wise) of the trigger as opposed to a longer squeeze with the S3.

Looking over the telemetry, it would seem that my previous cooling system was totally unnecessary as the motor temperature stayed in a safe range and I was pushing the truck more than usual today. The ESC spiked to about 72.3 C, but that was because I nailed the throttle at one point to avoid hitting a lamp post. Other things I saw were that I topped out at ~35 MPH (I had nowhere to open it up), peak current draw was 84.9 A, peak power was 861 W (~1.16 BHP). Something that caught my eye was the battery capacity readout. The telemtery said that by the end of the run I had ‘consumed’ 7251 mAH, but my battery is only 5300 mAH. That either means that my battery is badly underrated by the manufacturer and I got a very good bargain or there is an error with the readout.

I’ll likely go out tomorrow for another run to see what the capacity readout gives me. If it gives me a weird looking readout again I will use one of Hellhound’s 2200 mAH batteries to see how they perform and then I will move on to the 4S. If I get odd results with those as well then I might devise some kind of discharge bench-test at a constant rate of 1C or 2C to see how long they last.

Here are some screenshots of the telemetry data:

NOTE: I’m happy to share the telemetry files, if you want them for some reason, let me know. You’ll just need to download the free software to view them.

NOTE 2: The RPM curve is for motor RPM, however, I’ve told the software to give me the RPM at the wheels, so multiply the RPM figure by 12.13 to get motor shaft RPM or multiply by ((9.8pi) x (0.000372823)) to get speed in MPH.

All curves:

This one is a mess because I switched all the curves on and zoomed out so that you could see the whole run, the point of this is so that you can see all the numerical data at the bottom and not the curves.

Power / Voltage (the red flat-line is the cut-off level) / Current curves:

ESC and Motor temperature curves:

Capacity / Voltage curves:

This is the one that gave the odd reading, if the battery is 5300 mAH, then the battery voltage should have dropped to cut-off level (3.2V / cell) at around 1500 seconds, not at around 1960 seconds. I trust the voltage readout, and it partially supports the capacity readout being correct, but I have my doubts.

And as usual, here are some gifs from the run.

[lpfan61]

Yaaay!! New Banshee on the road!

[the_termin8r]

There’ll be more stuff tomorrow and probably for the day or two after as well.

[the_termin8r]

Banshee PRR:

Baseline run 2 / Capacity run 1:

Conditions were a lot better today, it was soaking wet and the slicks got some very good grip (you’d think the truck would be sliding around as if on ice, but no). As I found out, the best grip came from fine grain tramac (the black stuff) as opposed to regular concrete. I still don’t know why there is a massive increase in grip when it is very wet, but I know that I’m not imagining it. I deliberately tried to spin out or to slide the rear on the wet tarmac and the truck just rolled over.

The purpose of this run was to look at the capacity curve on the telemetry and compare it to the one from the first baseline run. Again, like with the first run, I was gettng a battery capacity that was way above what the battery was actually rated for. This time it gave me about 7054mAH which is close to what the last run gave.

Another strange thing I saw was the motor temperature curve, for the most part it looked fine, apart from very frequent dips to sub zero readings. The more correct curve would be if you just looked at the peaks. I think it might have something to do with the sensor wire being wet (the crimp connectors are exposed on the back of the motor-side plug). I’ll clean it, temporarily put some Blu Tack around the plug and go for another run tomorrow.

Tomorrow’s run will be with one of Hellhound’s 2200mAH 3S batteries so that I can see what capacity I get. The only issue is that they are also made by Overlander which means that they too could be underrated. The only non Overlander batteries / cells I have are the tiny 1S cells made by Turnigy I use on Camazotz. I suppose that as a last resort I can connect the 4 in a 2S2P arrangement and use it as a small 2S and drive very carefully as they are not designed for high current draw.

Here are the telemetry results:

Top speed for today was about 30 MPH, peak current was 87.7A, peak power was 871W (~1.17 BHP). I also noticed that the ESC maxed out at about 70C again and averaged at 60C, so my prediction of the spike being from sudden throttle yesterday seems to be wrong, the ESC just runs at those temperatures.

All curves:

Power / Voltage / Current curves:

ESC temperature / Motor temperature curves:

Capacity / Voltage curves:

In terms of gifs, there isn’t anything good, it was too dark and wet for the camera to actually catch anything without it being disorienting. So, I’m only sharing my attempt at a slide on wet tarmac that resulted in a roll.

[the_termin8r]

Banshee PRR:

Baseline run 3 / Capacity run 2:

The purpose of this run was to try a different 3S battery, observe its capacity and compare it to the claimed capacity. This time I was running the Overlander 2200mAH 3S that I run in Hellhound, and again, I was getting a capacity far greater than what Overlander claim. On one hand, that would explain why Hellhound was running so long on one charge, on the other, I’m still not fully convinced by the telemetry reading. The battery lasted about 20 mins on this run.

Conditions for this run were pretty bad, moist and very slippery. I spent most of the run trying to powerslide / drift (in a truck meant for neither of those things) so there won’t be many gifs. In these conditions the truck either spins out immediately or understeers like a pig. It’s mostly down to the tyres which work in either extreme (very dry or very wet), but not in the middle. The tyres are also in dire need of a change, but I want to get this set of runs on the same set of tyres for the sake of consistency, then I’ll swap them out.

For this run I put some blue tack around the motor sensor wire to keep the water out and I stuck my old phone to the transmitter so that the camera could stream to it over wifi, I wanted to try FPV driving with it. Although the Blu Tack kept the water out, I don’t think it was water causing the odd motor temperatue curve from the last run as I got the same sort of curve this time. Ignoreing the odd dips, the curve is actually perfectly fine, the average temperature is about the same as what I calculated by hand and the max is also on point, it’s just the minimum that gives a wrong reading.

The experiment with the phone did not go well, the camera had way too much latency and the phone decreased the range of the transmitter to about 10m. This is because the wifi connection operates at 2.4GHz, but so does the transmitter and receiver for the truck, they were just interfering with each other, so I ditched the phone.

For tomorrow’s run I will quickly put together a 2S2P lead for the single cells I have for Camazotz and go for a quick run with those. They’re from a different brand (Turnigy), so I’m hoping the capacity readout will be closer to what is claimed, if they too overshoot by a lot I’ll probably do some kind of capacity bench-test on all of them. There is a high chance that I might go for a 4S run as well.

Here are the telemetry curves:

The high current and high power readings are because I was trying to powerslide. Of course the RPM reading here can’t be used to estimate the top speed, again, because of the powersliding. You have to keep in mind that it is wheel RPM, not actual speed, it doesn’t account for wheelspin. If this was speed, I must’ve hit ~50 MPH at some point, which is not the case.

All:

Power / Voltage / Current:

ESC temperature / Motor temperature:

Capacity / Voltage :

It was claiming ~3300mAH from a 2200mAH battery.

The Blu Tack and phone experiments.

Here are a couple of gifs.

[the_termin8r]

Banshee PRR:

4S baseline run 1 / Capacity run 3:

I was supposed to be doing two runs today, one on a 2S2P setup and one on 4S. The 2S2P run lasted exactly 30 seconds. As I expected, the tiny Turnigy cells couldn’t supply enough current to get to about 5 MPH or to sustain that speed for more than 2 seconds. The truck covered a whopping 5m before the LVC cut in. The speed, distance and duration were so insignificant that the telemetry didn’t even record them, there isn’t any gif footage either as I forgot to hit the record button again.

I then swapped in the 4S, as anticipated some weeks ago, the run did not end well. It didn’t end as spectacularly as I expected but there’s still damage to repair. Conditions were pretty bad again, moist and slippery. The truck simply could not put down any of its power effectively to get up to any real speed with the current tyres. However, even in the slippery conditions, I could tell just how much extra power was available simply by the change in throttle sensitivity.

Rather surprisingly, through the course of the run, the motor temp stayed in a very safe range, the ESC got a little toasty, but nothing dangerous. What surprised me was that I got a little carried away with the throttle (this is what caused the run-ending damage) and didn’t drive as carefully as I planned. If anything, I drove slightly harder than usual and the motor stayed within a safe temperature range which really impresses me. The motor temperature curve also went back to looking almost completely normal, with only a couple of odd drops, but they didn’t cross the 0 mark.

As metioned a moment ago, the run didn’t end well (mainly due to my trigger happiness), I ended up stripping the idler gear quite badly around 20 mins into the run and that did some damage to the differential gear as well. It didn’t end as spectacularly as I’d predicted (exploding tyres or smoking motor or melting clutch), but it ended the run prematurely.

As well as getting baseline results for 4S running, the purpose of this run was to also test for capacity again, and again, the telemetry was claiming a lot more than the battery should have had in it (~4400mAH from a 3700mAH battery), and I hadn’t even hit the LVC, if the voltage reading is anything to go by, I was just past half way through the pack. I’m going to have to carry out some bench-tests at some point since the Turnigy experiment failed and I don’t own any other batteries not made by Overlander.

The stripped gears.

Technically the diff isn’t stripped, just damaged, but the idler clearly is. In the pic, the diff looks like it has lost all of its teeth, that is not the case. The diff housing is asymmetric and the teeth can’t be seen properly from the side seen in the pic. I took the pic from that side so that the differences in the tooth tips can be seen, otherwise the teeth would look fine.

Telemetry results:

Peak power for today was a pretty big 1760W (~2.36 BHP), peak current was 125.2A. As with yesterday, speed cannot be estimated from the RPM due to a lot of wheelspin on grass.

All:

Power / Voltage / Current:

ESC temperature / Motor temperature:

Capacity / Voltage:

I’ve noticed that the gif footage has become bumpier over the last few runs, I suspect that is because I lightened the truck, but still kept the same suspnsion stiffness. I’ll probably soften it a bit in a run or two as well as lower it by a few mm.

This is probably the smoothest jump landing I’ve ever had.

[rickvanmeijel]

@the_termin8r

It didn’t end as spectacularly as I’d predicted (exploding tyres or smoking motor or melting clutch), but it ended the run prematurely.

Lol! You secretly wanna destroy your creations?

[the_termin8r]

No, but I’m pushing my luck.

[the_termin8r]

Not really a project, but I spent the night modifiying the Lego rally car (42077) I got for xmas. The original was RWD and had no power functions. I modified it to be AWD and to be remote controlled. I can see why they didn’t make it AWD in the first place, it’s too much trouble. After my mods, the physical appearance was near identical. The mods include two M motors for drive, an M motor for steering (I don’t have a servo) and a standard AA battery box and non-proportional Tx/Rx combo.

The car itself is mostly the same, apart from the front where most of the redesign work was. It was too much trouble for the result I got. I had to use 6 shocks at the front, because of the available mounting points, the suspension just collapsed with 2 shocks. The car is also too heavy to move itself and there’s gears grinding somewhere deep in the bowels of the car. I don’t want to get back in to try and fix it, it’s too much trouble.

Stock:
https://forums.lpunderground.com/uploads/short-url/3QpSCAkiXWMW4FPTjc2BTz96drV.jpeg

Modified:

[StephLP18]

It looks really cool and it only took you all night to do it

[the_termin8r]

That’s because I improvised it, it wasn’t a great chassis to work on. Suffering from Lego fingers today, they’re quire sore. lol

[the_termin8r]

Quick update on Banshee. The parts came in today, so I replaced the ruined diff and idler, changed the tyres and decided to cover the underside of the truck in gorilla tape as a chassis protector.

Tomorrow will be the last run for a while as I continue to work on my dissertation. It will be a 4S run where I can hopefully finish the battery this time.

[lpfan61]

Looks cool!

[the_termin8r]

I want to see how the new tyres will perform, it’s the first time since the stock tyres that I’ll be running on tread and the first time I’ve taped the insides.

[the_termin8r]

Banshee PRR:

4S baseline run 2 / Capacity run 4:

I managed to get a good run this time, ran to the end of the charge with only one minor issue. The servo horn ballstud unscrewed itself from the servo horn and I had to screw it in by hand, it was a 3 min fix. I’ll tighten it down harder before the next run (I might even put a drop of superglue on the threads). Other than that, I had no issues, despite having several large crashes with a lot of tumbling and no breakages.

For this run I was running on fresh tyres that I also taped on the inside. The new tyres have a lot more grip than I expected, so much so that I’m going to have to lower the ride if I don’t want to flip over every time I chuck it into a bend. The braking is also greatly improved. The tape makes a huge difference, I can now afford to go faster in shorter distances without worrying about the tyres ballooning and unsettling the truck or even possibly exploding. As a result, the telemetry said I got to about 50 MPH this time, and although I did build up more speed than usual, I’d say it was closer to 45 MPH if I account for wheelspin and / or possible clutch slip. The only downside to the taped tyres is that they have a very slight imperfection in their shape, despite my efforts to apply the tape as well as I could. This doesn’t have an effect on the driving performance, but it does make camera footage a little shakier than normal, however, I have noticed that the gif maker seems to smooth the gifs out a bit for some reason.

Conditions were not bad this time around, cold and dry, good for the electronics and good for the tyres (despite the tyres being made to run in warmer weather). The ESC temperature stayed as I’d expect, but the motor was running surprisingly cool, I wasn’t running as hard as the last few runs, but I didn’t go too easy on it either. The motor maxed out at around 47C which is pretty much nothing considering that I’m running the motor past it’s specifications. To be honest, it’s nothing even if I run it within spec.

However, as before, the battery capacity curve was showing values that are way too high. I’ll try one last run with my old 6 cell, 4600 mAH NiMH that I’ve had since I got the truck. The battery has been used a lot and by now should be holding well under 4600 mAH of charge and it isn’t made by Overlander. So, if it too is reading well over what it is rated for, I’ll know that the telemetry is off on that reading. If it doesn’t, then there’s a chance that Overlander just grossly underrate their batteries (which means I’ve been getting great bargains and value for money). If the NiMH does give a correct reading I’ll do a bench-test on the LiPos with my discharge resistor to see what capacity I can roughly calculate.

Going back over all of the runs with telemetry data (not including the last run where I couldn’t finish the battery), there is an average error of about a +43% from what the battery claims. I don’t see the batteries being that badly rated from the manufacturers. I’d expect a ~+/-5% (~+/- 10% at the maximum) tolerance in the claim, not +43%.

I’ll try and squeeze the NiMH run in tomorrow if I have time, if I don’t, I can’t say exactly when I’ll be able to do it. The same goes for the bench-testing (if it comes to that), I don’t know when I’ll be able to do them.

Telemetry curves:

The odd gap in the middle of all of the curves is when I was fixing the servo horn.

All:

Power / Voltage / Current:
The power and current curves are almost identical.

ESC temperature: Motor temperature:

Capacity / Voltage:

Here are some gifs from the run, they include every crash.

This one carries on from the last one.

This is the highest speed I managed to get to today.

[lpfan61]

Niiiice gifs! too much crashes though… be careful!!!

Also you should bring with you a fast repairing kit!