Hot Newest Crawler Car in Gearbest (HG p402)
08-27-2015, 04:23 AM
#31
Can you please explain this statement?
This is what bothers me most about - to crawl the rocks really slowly with great precision, the car would need to be equipped with a CPU control to force the electric motor turn regardless of load (within reasonable limits of course). At least that's what I did on my Tatra 130. Again, this is a general problem of almost every RC car/truck.
My understanding of electronics tells me that a motor pulls electricity. If there is a trick to forcing a weak motor to turn I'd like to know what it is please.
This is what bothers me most about - to crawl the rocks really slowly with great precision, the car would need to be equipped with a CPU control to force the electric motor turn regardless of load (within reasonable limits of course). At least that's what I did on my Tatra 130. Again, this is a general problem of almost every RC car/truck.
My understanding of electronics tells me that a motor pulls electricity. If there is a trick to forcing a weak motor to turn I'd like to know what it is please.
08-27-2015, 08:04 AM
#32
Of course - you can force a DC electric motor to turn from a still stand giving it a correct pulse. You do it normally on a transmitter - you just press the "throttle" more, don't you?
A CPU can do it much faster and therefore the result can be also much smoother. Its best, if you read voltage on the motor (its directly proportional to revolutions), or read revolutions via a Hall sensor or some optical reading like on a PC mouse.
You can even force the motor to stand still when the RC model is on a steep slope.
Then you can implement a regular PID regulator on the CPU and force the electric motor to do interesting things.
The key trick is so: the CPU will read the PWM signal coming from the receiver, understand it, and it will produce another (corrected) signal for the motor regulator. As simple as that... the rest is just fine tuning the algorithm to suit the particular RC model.
That's basically what I did on my Tatra 130 RC model - I found out, that the truck needs a bit more power to turn the gears, especially in hard terrain. So from a still stand I give a short throttle pulse to the motor regulator. I was lucky to have a "dumb" regulator, which does exactly what it is told to do (via PWM signal) - i.e. it does not have any other artificial intelligence thinking something else.
A CPU can do it much faster and therefore the result can be also much smoother. Its best, if you read voltage on the motor (its directly proportional to revolutions), or read revolutions via a Hall sensor or some optical reading like on a PC mouse.
You can even force the motor to stand still when the RC model is on a steep slope.
Then you can implement a regular PID regulator on the CPU and force the electric motor to do interesting things.
The key trick is so: the CPU will read the PWM signal coming from the receiver, understand it, and it will produce another (corrected) signal for the motor regulator. As simple as that... the rest is just fine tuning the algorithm to suit the particular RC model.
That's basically what I did on my Tatra 130 RC model - I found out, that the truck needs a bit more power to turn the gears, especially in hard terrain. So from a still stand I give a short throttle pulse to the motor regulator. I was lucky to have a "dumb" regulator, which does exactly what it is told to do (via PWM signal) - i.e. it does not have any other artificial intelligence thinking something else.
08-27-2015, 11:13 AM
#35
hotrod87: No, I don't think so. You just need more precision in throttle control, which the transmitter doesn't offer. The battery is fine, the motor is fine. May be the ESC could be a little more intelligent and do the power pulses better, because it can measure voltage on the motor and therefore do the regulation (help the motor).
The key problem here is that human control is just a little slow observing the behaviour of the car and reacting adequately (pressing throttle more or less). This is where CPU control could help a lot - it could make the motor turn almost regardless of load. You can even simulate behaviour of a diesel engine with its inertia and other characteristics.
Or one can put much slower gear ratios in the car, then the motor will run at higher revolutions giving much higher torque to the wheels and the described problem will be less noticeable.
Please note, this is not a problem of the HG P402, since almost every RC car today behaves this way. We are talking about the art of DC electric motor control - electrical and software.
The key problem here is that human control is just a little slow observing the behaviour of the car and reacting adequately (pressing throttle more or less). This is where CPU control could help a lot - it could make the motor turn almost regardless of load. You can even simulate behaviour of a diesel engine with its inertia and other characteristics.
Or one can put much slower gear ratios in the car, then the motor will run at higher revolutions giving much higher torque to the wheels and the described problem will be less noticeable.
Please note, this is not a problem of the HG P402, since almost every RC car today behaves this way. We are talking about the art of DC electric motor control - electrical and software.
08-27-2015, 11:20 AM
#36
SteveM: absolutely, the P402 is an excelent and cheap choice, even for rock crawling. As I've already written, I was very impressed how well the car behaved on those rocks.
However, since I've successfully implemented CPU controlled realtime simulation of air cooled diesel V8 with 5+R virtual gearbox for my Tatra 130 (and thus forcing stock regulator and stock electric motor behave as a real truck), I can imagine, how much this would help the P402 even with its fast gear ratios.
However, since I've successfully implemented CPU controlled realtime simulation of air cooled diesel V8 with 5+R virtual gearbox for my Tatra 130 (and thus forcing stock regulator and stock electric motor behave as a real truck), I can imagine, how much this would help the P402 even with its fast gear ratios.
08-27-2015, 12:01 PM
#37
Just to be clear. I have had no issues with the electronics in the HG P601 I am doing a running review on. Throttlle has always been smooth and I understand the motor is weaker than I'd like but works good. Aside from the charger having an EU plug this is an honest rtr. It has been holding up great with no major issues. I have been through 2 of 3 diffs to reluble and assemble as with all 6 shocks and glue tires on otherwise have done nothing
09-06-2015, 08:19 PM
#42
bump.
The flash sale is finished successfully,thanks.
I will tell others the new flash sale timely.
Please expect it
The flash sale is finished successfully,thanks.
I will tell others the new flash sale timely.
Please expect it
09-20-2015, 12:57 PM
#43
Does the HG P402 behave well in snow? Well, hard to say in the summer in Central Europe (even in recent years, there is not too much snow at all). But there are locations, where one can find ice even in the summer. One of them is Hallstätter Glacier just below the Dachstein mountain in Austria.
I must admit, taking the HG P402 to Dachstein wasn't the primary purpose of our visit. We were looking for some nice alpine views and panoramas to photograph our RC models. The HG P402 was an ideal candidate though - it is robust enought to test the whole journey including transport to the mountain top , and it is an all-time four wheel drive with excelent off-road tyres.
At temperatures reaching 0 °C the HG P402 behaved well and reliably. The battery was fine and the car drove well through the icy terrain. Of course we didn't drive directly on the slippery glacier. And I'm not joking at this point - walking and driving on the glacier requires some serious ice equippment - ice chains on the wheels and crampoons for the driver and for the camera operator .
But the walk path was safe and we managed to take some interesting photos. We had all sorts of different weather up there - from cold gray clouds where one saw just a few tens of meters ahead to a few shots of sun and bright blue sky.
After we got back, I inspected the chassis thoroughly. There are a few scratches at the differentials and axle suspension rods from the last rock climbing session.
There is some looseness in the wheels and axles which hasn't been there when the car was brand new. The rear wheels have some 10° of loosenes between each other. Part of the loosenes is directly in the wheel-half axle mounting, the rest of it is in the final drive.
The front wheels are of similar state. There is some more loosenes in the front axle joints too.
On the other hand, there is no loosenes in axle suspension rods and or steering joints. We'll see how this evolves in next missions .
I must admit, taking the HG P402 to Dachstein wasn't the primary purpose of our visit. We were looking for some nice alpine views and panoramas to photograph our RC models. The HG P402 was an ideal candidate though - it is robust enought to test the whole journey including transport to the mountain top
, and it is an all-time four wheel drive with excelent off-road tyres. At temperatures reaching 0 °C the HG P402 behaved well and reliably. The battery was fine and the car drove well through the icy terrain. Of course we didn't drive directly on the slippery glacier. And I'm not joking at this point - walking and driving on the glacier requires some serious ice equippment - ice chains on the wheels and crampoons for the driver and for the camera operator
. But the walk path was safe and we managed to take some interesting photos. We had all sorts of different weather up there - from cold gray clouds where one saw just a few tens of meters ahead to a few shots of sun and bright blue sky.
After we got back, I inspected the chassis thoroughly. There are a few scratches at the differentials and axle suspension rods from the last rock climbing session.
There is some looseness in the wheels and axles which hasn't been there when the car was brand new. The rear wheels have some 10° of loosenes between each other. Part of the loosenes is directly in the wheel-half axle mounting, the rest of it is in the final drive.
The front wheels are of similar state. There is some more loosenes in the front axle joints too.
On the other hand, there is no loosenes in axle suspension rods and or steering joints. We'll see how this evolves in next missions
.
Last edited by drracer; 09-20-2015 at 01:03 PM. Reason: fix typo
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