Open Source Electric Supercharger

[neutron256]

Originally Posted by mid_life_crisis

@neutron256
What max rpm did your motor of choice end up having? Like many, I'm very curious as to what kind of cfm your creation is going to be capable of moving.

I've got two motors right now that I'm planning on trying.

-Turnigy AquaStar T20 (229amps Max Load)
41V Max (I'll be running 36V)
1280 RPM/V or 730 RPM/V
So a max for my configuration of 46K RPM

-Turnigy SK3 EDF (110amps Max Load)
30V Max
1500 RPM/V
Max of 45K RPM

There are a lot of considerations here though. First the max RPM's are theoretical no-load speeds, and I have reason to believe the specs for the Aquastar are not correct. Pretty safe to assume the actual RPM will be less then the max possible for that motor.

I'm also continuing to look at different motor options so if anyone sees something that might work let me know. Keep in mind we're looking for around 45K+ RPM and over 100 amps max load, probably closer to 150 amps.

Edit: Another consideration is shaft diameter. For my current design the shaft diameter needs to be greater than 6.5mm and then will turned down to the fit the compressor wheel.

[mid_life_crisis]

I find myself wondering about gearboxes, but I don't see anything capable of spinning at the rpm we need as being reliable or affordable. If you were to try simply offsetting the motor and using a couple of gears to increase the speed, I worry that the side load forces would make the turbine unstable. Could this be overcome by using three smaller motors as the points of a triangle with the turbine shaft in the center? The appropriate sized gears would ramp up the turbine rpm and the three driving gears might support the driven gear of the turbine and help keep it stable while three smaller motors added together could supply the necessary power to spin the thing.
Going further, a plate at each end of the assembly sandwiching the three motors could support a center shaft with a high rpm bearing at each end, allowing you to build it with the drive shaft diameter of your choice in the center. The output speed of the drive shaft would be established by the ratio of the gears. The design is simple and should be fairly rugged.

[neutron256]

Originally Posted by mid_life_crisis

I find myself wondering about gearboxes, but I don't see anything capable of spinning at the rpm we need as being reliable or affordable. If you were to try simply offsetting the motor and using a couple of gears to increase the speed, I worry that the side load forces would make the turbine unstable. Could this be overcome by using three smaller motors as the points of a triangle with the turbine shaft in the center? The appropriate sized gears would ramp up the turbine rpm and the three driving gears might support the driven gear of the turbine and help keep it stable while three smaller motors added together could supply the necessary power to spin the thing.
Going further, a plate at each end of the assembly sandwiching the three motors could support a center shaft with a high rpm bearing at each end, allowing you to build it with the drive shaft diameter of your choice in the center. The output speed of the drive shaft would be established by the ratio of the gears. The design is simple and should be fairly rugged.

Like I've said before, if you want to have step-up transmission centrifugal superchargers already exists and could be adapted. Designing a high-speed transmission is fairly simple, actually building it with the needed precision is a lot more difficult. The wear and tare is also something you need to keep in mind. Lubrication of a transmission like this is probably going to be very important.

I think for my extra power needs (which is really none) the direct drive is going to be just fine. But I would be curious to see if someone else comes up with a geared designed. I'd probably even be willing to help with the design/CAD if someone has a good concept, but I'll leave building and testing to someone else.

Edit: Also keep in mind as you try to get more compression that power has to come from somewhere. We're already talking about around 150 amps.

[mid_life_crisis]

Originally Posted by neutron256

Edit: Also keep in mind as you try to get more compression that power has to come from somewhere. We're already talking about around 150 amps.

True enough. What they are seeing on the other thread is that even one psi with no overhead during boost yields a worthwhile increase. Keeping that in mind, how much more power would it take?

[Calum]

Originally Posted by mid_life_crisis

I find myself wondering about gearboxes, but I don't see anything capable of spinning at the rpm we need as being reliable or affordable. If you were to try simply offsetting the motor and using a couple of gears to increase the speed, I worry that the side load forces would make the turbine unstable. Could this be overcome by using three smaller motors as the points of a triangle with the turbine shaft in the center? The appropriate sized gears would ramp up the turbine rpm and the three driving gears might support the driven gear of the turbine and help keep it stable while three smaller motors added together could supply the necessary power to spin the thing.
Going further, a plate at each end of the assembly sandwiching the three motors could support a center shaft with a high rpm bearing at each end, allowing you to build it with the drive shaft diameter of your choice in the center. The output speed of the drive shaft would be established by the ratio of the gears. The design is simple and should be fairly rugged.

What you described is called a planetary gear. By passing the drive shaft between the motors you have essentially created a quill shaft, which would aid in flexibility to help protect the load and motor from shock loads. An elegant design but I don't think the efficiency losses would make it worth the effort. A 1:2 ratio that gave ~90K rpm would be awesome though. With a motor controller to ramp up motor rpm as engine rpm ramped up the average draw wouldn't be as bad and the connecting rods would stand a chance vs 20 psi at 1500 rpm.

[neutron256]

Originally Posted by mid_life_crisis

It takes a few things to be able to do this.

1) Access to the necessary equipment.
2) The necessary skill set.
3) A slush fund.

You appear to be the only one with all three. More power to you, man. We're all watching to see what you come up with. When you get to the point where programming and electrical design come into play, there are others who can help, but for now it looks like it's you.
I, for one, say thank you for sharing what you're learning.

The electrical design is mostly complete since I'm using UniChip to directly control the compressor motor. The one thing I do still need to design is the charging system. For some reason a good setup for this with a 36V system just isn't coming to me.

I am also considering a larger turbo compressor like a Garret T-76 which will start making good compression around 35K RPM Larger inlet and outlet as well which should help reduce restriction. I'm considering using that for one of my prototypes. It uses a different backplate setup so I'd have to modify my design some.

[mid_life_crisis]

What keeps popping up in my mind when I think of this is a bank of relays wired up so that three identical batteries are wired in parallel and connected to the alternator's charging circuit. When you hit the activation switch, the relays switch and the batteries are in series connected to the electrocharger. You could wire in a voltage sensor that could trip a master relay in the event that one of the other relays ever stuck and the charging system would have seen more than one battery's worth of voltage.
It isn't exactly a new idea but it could work and you don't lose energy converting voltages.

[rusty959]

Originally Posted by mid_life_crisis

I find myself wondering about gearboxes, but I don't see anything capable of spinning at the rpm we need as being reliable or affordable. If you were to try simply offsetting the motor and using a couple of gears to increase the speed, I worry that the side load forces would make the turbine unstable. Could this be overcome by using three smaller motors as the points of a triangle with the turbine shaft in the center? The appropriate sized gears would ramp up the turbine rpm and the three driving gears might support the driven gear of the turbine and help keep it stable while three smaller motors added together could supply the necessary power to spin the thing.
Going further, a plate at each end of the assembly sandwiching the three motors could support a center shaft with a high rpm bearing at each end, allowing you to build it with the drive shaft diameter of your choice in the center. The output speed of the drive shaft would be established by the ratio of the gears. The design is simple and should be fairly rugged.

I believe this is the design I was describing in post #270 and is my current plan. Ive been researching bearings, shaft sizes, and gears that will fit and am getting a solid idea of what I want to do. Ill probably start some 3d modeling soon.

More or less I'm not spending too much time on the controller I was speaking of because I'm curious how well the unichip is going to work.

Originally Posted by mid_life_crisis

What keeps popping up in my mind when I think of this is a bank of relays wired up so that three identical batteries are wired in parallel and connected to the alternator's charging circuit. When you hit the activation switch, the relays switch and the batteries are in series connected to the electrocharger. You could wire in a voltage sensor that could trip a master relay in the event that one of the other relays ever stuck and the charging system would have seen more than one battery's worth of voltage.
It isn't exactly a new idea but it could work and you don't lose energy converting voltages.

So, basically you got the same idea Ive been thinking of and conveniently drew up last night:


Obviously this isn't a full plan and would have failsafes/fuses etc, but seems like a solid idea.

Ive been doing a bit of looking as far as suitable relays go, but this idea works well for me because I will just put it in the trunk and then it will be perfect for stereo duties as well. If I use some xs power d925's Ill only be adding 20-30 lbs of battery weight but will have significantly more capabilities.

[Grantmac]

Ern:
http://www.ft86club.com/forums/showp...postcount=1339

Just saying.

[rusty959]

Originally Posted by Grantmac

Ern:
http://www.ft86club.com/forums/showp...postcount=1339

Just saying.

Yeup, same idea. I'm still trying to catch up on that thread, but thanks for pointing that out.

[neutron256]

Originally Posted by rusty959

So, basically you got the same idea Ive been thinking of and conveniently drew up last night:


Obviously this isn't a full plan and would have failsafes/fuses etc, but seems like a solid idea.

Ive been doing a bit of looking as far as suitable relays go, but this idea works well for me because I will just put it in the trunk and then it will be perfect for stereo duties as well. If I use some xs power d925's Ill only be adding 20-30 lbs of battery weight but will have significantly more capabilities.

I like the idea of a charge-in-parallel / discharge-in-series system.

A few notes on you design:

-When the supercharger is in operation I'm pretty sure it will need to be electrically isolated from normal 12v/chassis-ground.

-DC solenoid relays of this size (36V / 200 Amp) as far as I can tell only come as single pole. I'll keep looking they may be out there. A different layout could uses lower voltage/current relays which come in STDT versions in parts of the circuit.

-Solenoid relays of this size are pretty expensive. So far what I've found start around $80 (x4 = $320) but better deals may be out there.


I hope you won't think I'm just criticizing. Overall I like the concept, I was trying to come up with my own but apparently my brain is only good for analyzing other people's designs at the moment.

[rusty959]

Originally Posted by neutron256

I like the idea of a charge-in-parallel / discharge-in-series system.

A few notes on you design:

-When the supercharger is in operation I'm pretty sure it will need to be electrically isolated from normal 12v/chassis-ground.

-DC solenoid relays of this size (36V / 200 Amp) as far as I can tell only come as single pole. I'll keep looking they may be out there. A different layout could uses lower voltage/current relays which come in STDT versions in parts of the circuit.

-Solenoid relays of this size are pretty expensive. So far what I've found start around $80 (x4 = $320) but better deals may be out there.


I hope you won't think I'm just criticizing. Overall I like the concept, I was trying to come up with my own but apparently my brain is only good for analyzing other people's designs at the moment.

it should be good to go with a common ground for the system, as long as everything uses the same ground in the entire system. I see nothing that could cause any issues, feel free to point one out if you see it. This gives the side benefit that if this setup would be the only batteries in the car as I would plan on, you still have a 12v hooked up at all times.

yes, relays and associated cost is an issue, but I feel this is offset by not needing a dedicated charger. The idea im currently looking at is using multiple smaller relays in the 40-50 amp range. Since resistance in the relay should increase with temperature, it should be safe to run a few in parallel. I need to do more research on this. Im spitting off a lot of ideas before I fully think them through, but atleast that allows group thinking. Dont hesitate to criticize, as long as we are being civil it can only help understanding.

[mid_life_crisis]

Originally Posted by rusty959

it should be good to go with a common ground for the system, as long as everything uses the same ground in the entire system. I see nothing that could cause any issues, feel free to point one out if you see it. This gives the side benefit that if this setup would be the only batteries in the car as I would plan on, you still have a 12v hooked up at all times.

yes, relays and associated cost is an issue, but I feel this is offset by not needing a dedicated charger. The idea im currently looking at is using multiple smaller relays in the 40-50 amp range. Since resistance in the relay should increase with temperature, it should be safe to run a few in parallel. I need to do more research on this. Im spitting off a lot of ideas before I fully think them through, but atleast that allows group thinking. Dont hesitate to criticize, as long as we are being civil it can only help understanding.

It needs one more relay. Lose the connection to 12V on the left. The last relay has the 12/36 as the (I'm blanking on the technical name) common contact that actually moves, the other two are the alternator and the electrocharger so it is either charging or driving the EC. A system like this should have all its batteries isolated from the battery the car runs off. If you want 36 volts, you should have four batteries.

[mid_life_crisis]

Originally Posted by neutron256

-DC solenoid relays of this size (36V / 200 Amp) as far as I can tell only come as single pole. I'll keep looking they may be out there. A different layout could uses lower voltage/current relays which come in STDT versions in parts of the circuit.
:

Did you mean SPDT? His layout works with SPDT. Takes more of them obviously, but it pretty clearly does not require DPDT.