adding a 'sort of' turbo

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fletchlives76
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adding a 'sort of' turbo

Post by fletchlives76 »

is this possible????

I am going to buy the etek motor kit, and possibly a 2nd motor for my first attempt at building an EV motorbike.

The first motor would be set up powered by its batteries...and I was thinking of wiring the 2nd, or smaller motor up to run as a dc generator off the first motor, additional power that is generated by the 2nd motor could be supplied back into the main drive motor as a 'sort of' turbo providing those extra watts of power.

I see a use for this extra power in emergency burnout situations, overtaking large trucks and climbing the big hills.








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adding a 'sort of' turbo

Post by Electrocycle »

that second motor working as a generator will consume more power from the main motor than it can ever give back.

The best way to get a turbo effect is to have a temporary increase in the controller current limit, and drive the main motor harder.

Also, fitting two motors in a bike is not easy when you have all the other bits to fit in, and it complicates the drive train.
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adding a 'sort of' turbo

Post by antiscab »

Hi Fletchlives,

what you describe is indeed a perpetual motion machine.

i agree with electrocycle, just buy a bigger controller.
my bike came with a "turbo" button....one of the most useless ideas i have ever seen. why would you have extra power avail only sometimes.

what bike are you converting?
what size rear wheel does it use?
you can get 6kw continuous hub motors, but ive only seen them in 13" wheel size, which is probably a bit small for anything but a maxi-scooter.

biggest bldc controller ive seen so far is 120v 400A.

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Post by Simon »

I have been thinking about the idea of a turbo of sorts lately. By feeding a compressed gas (nitrogen?!??) for more cooling/effeciency into a DC motor so you can run heaps of amps through the motor? Does this idea have any merits?

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Post by Electrocycle »

CO2 is the most cost effective extra cooling (fire extinguisher type bottle with a solenoid valve), but since most electric motors have a high thermal mass you can get away with moderate but constant cooling - assuming you're only overdriving the motor for short periods.

A decent electric cooling fan feeding the motor will improve power handling a fair bit.
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adding a 'sort of' turbo

Post by fletchlives76 »

Ok, I have scrapped the idea of using gear reduction to drive my mbike as this would need a lot of force on the drive cog, and force requires power, and power is limited.

The bike will run using an etek motor set up kit. I have the link for the site which is in the US and their price is about $1000US.

THe 2nd motor, will be a much smaller DC type, probably sourced from ebay. This will be connected to the main drive motor and the power generated can be put back through the controller and give the drive motor some extra oomph.

This loop will stay away from the batteries and only be activated into the system when I press a small red button using my thumb. I could also use this as a power source for the lights.

THe 2nd motor will be attached via a coupling to the main drive motor.

I'm butchering some cooling fan motors I have lying around the house to see if the theory is correct.

I will post the results after the weekend but now its beer time.



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adding a 'sort of' turbo

Post by fletchlives76 »

Simon wrote: I have been thinking about the idea of a turbo of sorts lately. By feeding a compressed gas (nitrogen?!??) for more cooling/effeciency into a DC motor so you can run heaps of amps through the motor? Does this idea have any merits?


I don't think nitrogen is that safe when exposed to anything slightly warmer than a badgers freshly laid turd.

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adding a 'sort of' turbo

Post by juk »

"I don't think nitrogen is that safe when exposed to anything slightly warmer than a badgers freshly laid turd."

Nitrogen comprises 78% of the earths atmosphere as molecular nitrogen. Stable as.

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adding a 'sort of' turbo

Post by antiscab »

fletchlives76 wrote:
THe 2nd motor, will be a much smaller DC type, probably sourced from ebay. This will be connected to the main drive motor and the power generated can be put back through the controller and give the drive motor some extra oomph.

This loop will stay away from the batteries and only be activated into the system when I press a small red button using my thumb. I could also use this as a power source for the lights.


yup, still perpetual motion machine territory.
you might not believe it till you've built it, but when you hit that red button, your acceleration will be significantly *less* than before you hit it.
you might stop accelerating all together, depending on your setup.

the only way to get more power to the ground, is to draw more from the batteries.
so that means bigger or better batteries (or both).
and possibly a more powerful controller, depending on which controller you intend to use.

Matt

EDIT: missed a couple of words
Last edited by antiscab on Fri, 06 Mar 2009, 18:30, edited 1 time in total.
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adding a 'sort of' turbo

Post by woody »

Yep.

Generators take power to turn (that's why wind farms only work when it's windy).

There are losses at every step:

So
the mechanical power to turn the generator is more than
the electrical power generated, which is more than
the extra electrical power to your main motor, which is more than
the extra mechanical power in your main motor.

even if each step is 95% efficient, you still lose 15% to heat, definitely no gains.

If you're set on a boost, just rig your twist accelerator to only go to 80% unless you hit the turbo button to get the full 100%.

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Post by Richo »

Sorry Fletch but it won't work.
You can waste your life trying but it WILL FAIL.

Here is a typical example.

You are using 10kW of battery power into the controller.
The controller is 98% efficient.
So 9.8kW comes out of the controller.
Now the 9.8kW goes into an eTek motor.
The eTek is 85% efficient.
So 8.33kW is being turned into mechanical energy.
Now you cog/chain is 95% efficient.
So 7.91kW is reaching the rear wheel of your bike.

Now you press your "red button".
The 8.33kW of mechanical energy from the eTek has 1kW now being consumed by the "smaller" a second motor.
Now that 1kW going into the 2nd motor is only 80% efficient.
so coming out of the 2nd motor is 0.8kW which is fed back into the controller.
Now the controller is getting 10kW from the battery + 0.8kW from the motor.
Thats 10.8kW! Bonus.
Now the controller we already said was 98% efficient.
So 10.8kW goes in 10.58kW comes out.
The 10.58kW goes into the eTek (85%) and comes out 8.99kW
Of the 8.99kW 1kW is used by the 2nd motor.
So 7.99kW goes to the gears.
And now 7.59kW gets to the rear wheel.

Hang on before you pressed the red button you had 7.91kW at the rear wheel. Image
So you have LOST 0.32kW mechanical power by pressing your 'soft' turbo red button.
AND your bike slows down. Image

Sorry there are no free rides in this universe. Image


Also Nitrogen is an inert gas and would work.
Also reduce brush arcing so more volts could go in.
But the temp wouldn't be that much lower to be really noticable.
Now if you were jetting liquid nitrogen in controlled amounts would be good.
But rather expensive.

Sorry it's back to the drawing board Fletch. Image
So the short answer is NO but the long answer is YES.
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Post by Richo »

One way to get such a desired effect is to use ULTRACAPS. Image
And I can tell you now that the price for the Ultracaps you could spend on a bigger motor and better batteries for even better performance in the first place.
So the short answer is NO but the long answer is YES.
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Post by fletchlives76 »

I thought nitrogen gas was flammable???

The 2nd motor spins at the same time as the primary motor. The connection is mechanical and on the same shaft and spins whenever the rear wheel is moving.

I sort of understand what your saying...and will look at these motors in action to measure power loss and gains when my ebay multimeter arrives....





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Post by antiscab »

fletchlives76 wrote: I thought nitrogen gas was flammable???
your probably thinking of nitrous oxide, which isnt actually flammable either, but decomposes at high temperature into nitrogen and oxygen
reason its used in drag racers is because on the compression stroke, the decomposing nitrous oxide absorbs some of the heat, meaning you can cram more fuel into the cylinder without suffering pre-detonation.
the oxygen it liberates also means the extra fuel has something to combust with.

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Post by weber »

antiscab wrote:your probably thinking of nitrous oxide, which isnt actually flammable either, but decomposes at high temperature into nitrogen and oxygen
reason its used in drag racers is because on the compression stroke, the decomposing nitrous oxide absorbs some of the heat, meaning you can cram more fuel into the cylinder without suffering pre-detonation.
the oxygen it liberates also means the extra fuel has something to combust with.
That's almost right. Nitrous Oxide does have two separate effects when used with an internal combustion engine. It's stored as a liquid under pressure, so first it chills the incoming air in the intake manifold or intake port simply by its latent heat of evaporation and expansion. Cold air is more dense so a greater mass of air-fuel mixture can be taken into the cylinder on the intake stroke. It does nothing special on the compression stroke, but on ignition it decomposes and provides more oxygen to oxidise the fuel, and the decomposition itself is exothermic (giving off heat) causing even more expansion force. A good way to wreck an engine if it isn't designed for it.

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Post by antiscab »

looks like i was half right, nitrous does indeed give off heat when decomposing.
i should have seen that one, since nitrogen gas has the lowest enthalpy.
ah the yr12 Chem is coming back to me now.

good call weber.

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Post by Richo »

fletchlives76 wrote:The 2nd motor spins at the same time as the primary motor. The connection is mechanical and on the same shaft and spins whenever the rear wheel is moving.
It really doesn't matter how you transfer the power from the first motor to the second motor or how it is connected.
It will always involve losses that will make the bike perform worse.

Even if you had a 2kW 97% super efficient Permanent magent motor (read $12,000) as the second motor it is still going to make your bike 3% worse off.

Would you like to spend $12,000 to make your bike 3% worse?
So the short answer is NO but the long answer is YES.
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Post by Richo »

Richo wrote: One way to get such a desired effect is to use ULTRACAPS. Image


Here is an example of a go-kart using ultra-caps for a boost.
http://web.mit.edu/first/kart/
So the short answer is NO but the long answer is YES.
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