Need help to keep from blowing motor number 3
09-18-2001, 04:48 AM
#11
Senior Member
Join Date: May 2001
Posts: 1,436
Likes: 0
Received 0 Likes
on
0 Posts
Ok, I have a few key elements that have not been addressed, which leaves a lot of questions in my head as to how you can actually make this work...
First, the BETA motor isn't especially volumetrically efficient because of the cylinder head design, so let's say (for argument) that our motor has a top volumetric efficiency of 80%. This means at the peak of it's efficiency range, it will flow approximately 189 cubic feet of air per minute (IF that 80% holds true at 6700 RPM's)
In order to hold a 5psi intake charge on this motor, you would need a compressor capable of flowing 253 cubic feet of air per minute.
First thing: Where can you find an electric fan small enough to fit in your intake that is capable of flowing 253 cubic feet of air per minute?
But that's not all...
Secondarily, once you find such a fan, you will need to run it. Perhaps the fan assembly by itself could be small enough to fit in your intake (hell, a turbo impellor is that small) but you still need to rotate that assembly fast enough to move the air.
The problem now? Electrical demand. Let's say you found yourself a fan that can displace seven cubic inches of air per revolution (feasible for the intake size)... You need to turn that fan at almost 65k RPM's in order for it to push that kind of air through. Finding an electrical motor that can turn at 65K RPM's isn't likely going to happen, instead you're going to have to build a gearset. And with such a gearset, you will suffer mechanical losses because of the gearing.
The end result? Based on a subject very similar to this one on ClubSi, you will need an electrical motor capable of delivering 5 horsepower to that little fan of yours. The further result? You need 3.7KW of power, or 12VDC at 308 amps. Did you read that? THREE HUNDRED AND EIGHT AMPRES. Nope, that's not happening.
A 2 farad 16v capacitor could get that motor started for... oh, about 0.3 seconds before they fully discharge. Not to mention the huge install space you'll need for that motor, or the associated fan, or all the capacitors needed, or the HUGE alternator you'll need.
I am in serious doubt of this project. Unless you can provide pictures of the device (and MOVIES would be much better) or at least Dyno sheets that can be verified by an outside source, then I proclaim either BS or a fruitless engineering attempt.
My $0.02,
-Red-
First, the BETA motor isn't especially volumetrically efficient because of the cylinder head design, so let's say (for argument) that our motor has a top volumetric efficiency of 80%. This means at the peak of it's efficiency range, it will flow approximately 189 cubic feet of air per minute (IF that 80% holds true at 6700 RPM's)
In order to hold a 5psi intake charge on this motor, you would need a compressor capable of flowing 253 cubic feet of air per minute.
First thing: Where can you find an electric fan small enough to fit in your intake that is capable of flowing 253 cubic feet of air per minute?
But that's not all...
Secondarily, once you find such a fan, you will need to run it. Perhaps the fan assembly by itself could be small enough to fit in your intake (hell, a turbo impellor is that small) but you still need to rotate that assembly fast enough to move the air.
The problem now? Electrical demand. Let's say you found yourself a fan that can displace seven cubic inches of air per revolution (feasible for the intake size)... You need to turn that fan at almost 65k RPM's in order for it to push that kind of air through. Finding an electrical motor that can turn at 65K RPM's isn't likely going to happen, instead you're going to have to build a gearset. And with such a gearset, you will suffer mechanical losses because of the gearing.
The end result? Based on a subject very similar to this one on ClubSi, you will need an electrical motor capable of delivering 5 horsepower to that little fan of yours. The further result? You need 3.7KW of power, or 12VDC at 308 amps. Did you read that? THREE HUNDRED AND EIGHT AMPRES. Nope, that's not happening.
A 2 farad 16v capacitor could get that motor started for... oh, about 0.3 seconds before they fully discharge. Not to mention the huge install space you'll need for that motor, or the associated fan, or all the capacitors needed, or the HUGE alternator you'll need.
I am in serious doubt of this project. Unless you can provide pictures of the device (and MOVIES would be much better) or at least Dyno sheets that can be verified by an outside source, then I proclaim either BS or a fruitless engineering attempt.
My $0.02,
-Red-
09-18-2001, 04:54 AM
#12
Senior Member
Join Date: May 2001
Posts: 1,436
Likes: 0
Received 0 Likes
on
0 Posts
Ooops, one quick correction...
You will need a SEVEN horsepower electric motor to drive that fan assembly, which means my 3.7KW is too low. The correct calculation would be 5.2KW, or 12VDC at 433 ampres.
A six-pack of 2 farad caps wouldn't keep that motor running for more than a full second.
-Red-
P.S. I keep thinking of things to add... The power figures I have quoted above are based on 100% efficient mechanisms, which NEVER exists in real life. Electrical motors typically have a 68% efficiency rating, so that 5.2KW is actually VERY low too. Consider a realistic estimate to be around 8KW, and modify the VDC/AMPS accordingly.
[ September 18, 2001: Message edited by: Red ]
You will need a SEVEN horsepower electric motor to drive that fan assembly, which means my 3.7KW is too low. The correct calculation would be 5.2KW, or 12VDC at 433 ampres.
A six-pack of 2 farad caps wouldn't keep that motor running for more than a full second.
-Red-
P.S. I keep thinking of things to add... The power figures I have quoted above are based on 100% efficient mechanisms, which NEVER exists in real life. Electrical motors typically have a 68% efficiency rating, so that 5.2KW is actually VERY low too. Consider a realistic estimate to be around 8KW, and modify the VDC/AMPS accordingly.
[ September 18, 2001: Message edited by: Red ]
09-18-2001, 06:06 AM
#14
Member
Thread Starter
Join Date: Jun 2001
Posts: 96
Likes: 0
Received 0 Likes
on
0 Posts
I didn't realize those were the numbers that my brother was playing with. I'll call him today and ask some very specific questions, cuz HE was the one who did the calculations...
Maybe i can hardwire a voltage inverter, and add a leaf blower with the beefed fuel pump...
""turbocharger by Weed-Eater""
anyway, at least i still have my superconducting CAI smile.gif
Just wait till i get a hold of my brother..
Chris..
Maybe i can hardwire a voltage inverter, and add a leaf blower with the beefed fuel pump...
""turbocharger by Weed-Eater""
anyway, at least i still have my superconducting CAI smile.gif
Just wait till i get a hold of my brother..
Chris..
09-18-2001, 06:23 AM
#15
Senior Member
Join Date: May 2001
Posts: 1,436
Likes: 0
Received 0 Likes
on
0 Posts
Well now, consider that a leaf blower would be very similar in power draw.
When you plug your leaf blower into the wall socket, you are plugging into 120VAC. At 120 volts, you would only need a 30 amp draw to pull enough power for a 3HP fan.
But that same draw would be 300 amps on your inverter, which is fully unsustainable. You'd pop the little fuse in the inverter before you got anywhere.
The idea of a leafblower was a GAS powered leaf blower.
-Red-
When you plug your leaf blower into the wall socket, you are plugging into 120VAC. At 120 volts, you would only need a 30 amp draw to pull enough power for a 3HP fan.
But that same draw would be 300 amps on your inverter, which is fully unsustainable. You'd pop the little fuse in the inverter before you got anywhere.
The idea of a leafblower was a GAS powered leaf blower.
-Red-
09-19-2001, 08:36 AM
#18
Senior Member
Join Date: May 2001
Posts: 440
Likes: 0
Received 0 Likes
on
0 Posts
Hey I found a 4" fan that plows 230 cfm on a 12v system. I am sure that you could probably find a fan small enough to use!
What does 230cfm translate into? Its gota be close to the 5 psi that you are looking for!
Hey red do some math will ya!
you crunch numbers pretty good!
I will fiddle with this combo at my place and see what happens!
What does 230cfm translate into? Its gota be close to the 5 psi that you are looking for!
Hey red do some math will ya!
you crunch numbers pretty good!
I will fiddle with this combo at my place and see what happens!
09-19-2001, 09:50 AM
#19
Senior Member
Join Date: May 2001
Posts: 1,436
Likes: 0
Received 0 Likes
on
0 Posts
The problem is this: That fan could potentially flow 250 cubic feet of air per minute, but it's measured in FREE AIR. This means there is no resistance (except for normal air density) that would restrict the fan blades.
This does not occur in a pressurized system.
Such a fan would be lucky to generate 0.1psi above atmospheric, especially running on 12vdc at even 30 amps.
Again, to keep a fan moving enough to build pressure into the intake, you will have to make sure it's spinning VERY fast, and that it's a very "hefty" fan. 7hp is the approximate number you need to aim for.
This is why you NEVER have seen a good electric turbocharger anywhere. They simply require way too much power to be effective.
-Red-
This does not occur in a pressurized system.
Such a fan would be lucky to generate 0.1psi above atmospheric, especially running on 12vdc at even 30 amps.
Again, to keep a fan moving enough to build pressure into the intake, you will have to make sure it's spinning VERY fast, and that it's a very "hefty" fan. 7hp is the approximate number you need to aim for.
This is why you NEVER have seen a good electric turbocharger anywhere. They simply require way too much power to be effective.
-Red-
09-19-2001, 03:49 PM
#20
Senior Member
Join Date: May 2001
Posts: 598
Likes: 0
Received 0 Likes
on
0 Posts
Hey Red, have you ever heard of the "Turbo Zet"? It was an electric supercharger. Found it on the net last year or so.
Don't know anything about it just wondering.
Also had a twin blade version as well.
Don't know anything about it just wondering.
Also had a twin blade version as well.