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WHY WHY WHY can't I post Answered

Am unable to post a question or open a topic WHY.

I forgot this won't get posted. Dammm

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rickharris

4 weeks ago

IF this worked, Then the system has been very unreliable and erratic over the past week or so..

Now my REAL question that I asked a week ago.

My electric racing car had a 250 watt DC motor that weighed around 4 or 5 Kg.

Now this motor claims to be 4 K watts.
https://hobbyking.com/en_us/turnigy-c580l-580kv-brushless-inrunner-motor-4000w.html

Other than electric bikes I seen lightweight cars or velomobiles using such a motor why not. Am I missing something. The RPM will be very high but a suitable gear box isn't beyond engineering.

So why are they not in common use? $000 watts is 4000 watts in my book. (about 5.5 HP)

Expert opinion?

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Downunder35mrickharris

Reply 4 weeks ago

It seems I am NOT the only one experiencing this.
Started to think I am imagining the struggles.

Now to your actual problem...
I simply guess you had a normal, brushed DC motor as the original.
Brushless DC motors that basically work like a three phase AC motor are labelled differently fo various reason - none that make too much sense though if you ask me.

"Electrical" values...
Your DC motor might have been for 180V or so and had a max speed of lets say 400 RPM with no load at the set 180 Volts.
Means you know the torque and speed go down with an increased load while the Amps go up accordingly.
A brushless motor like the one you linked comes rated at 580kV.
Bad online seller making 580 Kilovolts out of this only add to the confusion.
In reality it stands for Thausand RPM per VOLT.
Meaning at 10 Volts it would already spin at about 580.000 RPM.
Again both sellers and stores add to the confusion by messing with this value as in reality those motors actuall are rated at 580 RPM per volt.
Correctly labelled it would then actually read 0.58kV.
Quite often only checking the datasheet or actually asking clear this up properly.
The other issue is the stated Watt the motor can tolerate.
The higher the RPM the less chance for a lot of heat to build up in the windings.
Like your normal DC motor it will be heat up much quicker at low RPM with a high load.
There are no real limits for the operating voltage of a brushless DC motor either.
Whatever the controller can provide will be accepted.
And since these usually go along with certain Voltages from the S combination of battery packs....
48V is still considered save enough for a human and usually is the max for standard brushless motors.
Higher than this usually means the application is fixed, like in a machine mounted to the floor - with proper isolotaion and all.
Like whe dealing with mains power...
If we take these 48 Volts and the stated 4000W we get a max of about 83 Amps.
This certainly can only be for short bursts and with forced fan cooling or similar to keep the windings cool.
But just doubling the voltage and we get about 40 Amps...
Again the confusion wouldn't be perfect if some manufacturers and sellers would "translate" the power to the speed of a normal DC motor.
In these cases they would simply divide the Watts with the RPM's.
For example if a standard 200W DC motor does its job at just 5000RPM while the brushless cousin makes it to a max of 25.000RPM the divide the max Watt of the brushless motor by 5 to match the RPM.
Or the other way around by multiplying the Watt value of the DC motor accordingly.

Whether or not you can use a brushless DC motor without a gearbox to replace the 250W DC motor depends on many factors.
Most of all the corresponding speeds, voltages and torque values.

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rickharrisDownunder35m

Reply 4 weeks ago

Thanks for that DU you simply confirm my thoughts.

In the original post I put a lot more details but lost the will to live after the 3rd try.

my original motor was indeed a brushed motor although 24 volt running at a max of 17 amps. At this level it got fairly hot and we cooled with a fan. The 250 watt rating was continuous use. 3000RPM geared 14:1 to the wheels. to give a theoretical max speed of 35 MPH.

As brushless motors are fairly cheap my second thought was you could run 2 or 3 or 4 in parallel to increase the available power. Even a one or two Hp would be fairly significant in a very light single person car on the flat.

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seamsterrickharris

Reply 4 weeks ago

Very odd indeed - I see it as an unpublished draft but likewise even as an admin I cannot muscle it through to published status. I've sent in a report to the engineer team to investigate.

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rickharrisseamster

Reply 4 weeks ago

Thanks - again if I click the link in the email it takes me to the front page. not to your reply.

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seamsterrickharris

Reply 4 weeks ago

Try logging out and back in, and let me know if it works after that. Ah, hmm. Links from emails not working might be a known issue for some users. Does the link work onsite, from the actual comment?

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rickharrisseamster

Reply 25 days ago

30/april update the link now takes me to the correct place, however the draft instructable link still tales me to the front page.

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rickharrisseamster

Reply 4 weeks ago

Log out log in same problem

Links from my profile page all return to the main page.

If that's any help.

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Downunder35mseamster

Reply 4 weeks ago

The links fail to work for quite some time now.
Whatever is inside an Email ends in the digital nirvana except for the links to Ibles and the actual topic.
Nothing with replies works, neither directly from the Email, nor the profile.
A lot of things simply won't publish at all, be it a new topic or changes made.
Right now the only thing that still works is opening a tab with the topic in question and use the normal reply button there.
The text entering bug I mentioned months ago is still present as well.
I now know I really need to get the mouse in the right spot of the text field to be able to type but I somehow doubt the majory of users will figure this out through trial and error.

Which brings me to the point:
Since all these problem accumulate now for over a year, what are the chances for getting proper updates on the (planned) fixes, improvements and fault removal?
No offence, but if after over a year the same bugs are still present then at least I get that nagging feeling of missing priorities.
As said many times:
Change and improvements might be a good idea but only if they actually work, won't break other things or simply annoy the crap out of the user.
A lot of feedback, bug reports and so remain unaddressed.
Every time I start to get the feeling it might get better now someone adds new stuff to break even more than what was already broken here :(
If years of patching holes end nowhere than it would time to consider a proper platform for the cummunity section instead of a homebrew solution.

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Downunder35m

4 weeks ago

Tried to post a new topic....
Once done I clicked the fancy orange button.....
"loading" appeared on the button...
I wait...
I wait...
I wait a bit longer but no change.
I take a snooze and check again : "loading".

I can post replies, I can check my profile, I can do the lot, just not post a new topic.
Does not happen all the time, sometimes it just works fine.
But it fails often enough for me to ask myself why I still bother to try :(

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Downunder35mDownunder35m

Reply 4 weeks ago

Well, checked again and the loading finally stopped.
Got the "Publish" button back :)
Only too bad that using it only brings back the loading with no end in sight LOL

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Downunder35mDownunder35m

Reply 4 weeks ago

No clue who code changes work here but maybe it would be a good idea to give a warning note on the screen?
Maybe a re-director to a page telling us that work is being done and that all back up shortly?
To just dream with a set time?

Am just glad I did not do it with an Instructable but a rather useless topic.
When I came back I was told change is happening and all we be good again soon.
Maybe other have more luck but for me this only causes a lot of frustration every time I come here.
Already started to call it a good day if I don't get any failures ROFL