Open Source Electric Supercharger

[neutron256]

Originally Posted by rusty959

Can you better describe the stalling at startup? It is reasonably common for unsensored brushless motors to have a bit of issue starting moving from a standstill, commonly referred to as "cogging". Try giving it only enough throttle to have it spin and then going wide open and see if that makes a difference.

The high rpm stuff may very well be an ESC issue, but don't be too mad if the low rpm isn't any different.

Yeah you pretty much nailed it. It seems to need a burst on the throttle to get it going but it's a narrow window between enough to start it, and too much causing ESC to cut out.

I think the new ESC should do the trick. I'll have to take the "cogging" issue into consideration when configuring a map to control the motor.

[neutron256]

For those looking for a solution for charging 24v/36v battery banks I think I've come across a really excellent product.

Minn Kota 2/3 bank alternator charges.

http://store.minnkotamotors.com/prod...C_%283_bank%29

These are designed to charge battery banks for electric trolling motors and can balance charge the batteries in series from a 12v source without needing to break the series connection between them.

It looks to be an excellent solution and they can be found for $106 for the two bank (24V) or $138 for the 3 bank (36v) version on Amazon.

[rusty959]

So just to give an update on what ive been doing, the short answer is not much. Mostly this is due to buying a house as Ive stated a few times, but more so Ive really been thinking about the feasibility and point of going e-supercharger.

One of the main reasons I wanted to do this and do it big was the ability to decouple the boost from engine RPM. Obviously I had plans from the start to be able to highly tune what boost I wanted where. However, I didn't realize how bad high boost at low rpms was for an engine. Obviously, tune makes a difference, and building the engine will resolve it from being an issue, but if without opening up the block I can't run uber boost at low rpms, Ive lost part of the reason I wanted to do this.

My second issue creeping up is I will be leaving in June for some military training that will last about a year. While I am convinced that a setup such as what Neutron is doing or the phantom setup can run reliably, my proposed system can't. While a little bit of upkeep is fine, even to the point of changing out gears, the system as a whole probably wouldn't be ironed out in 6 months, and Ill need a reasonably reliable car through that year.

My current tentative plan moving forward is the Kraftwerks rotrex kit, for a couple reasons. One of the most important reasons for this thread is that it has a second belt system, offset from the factory one. This will make a perfect start to not use the crank pulley and fab up a couple electric motor mounts. Especially considering these brushless motors can run either direction with no issues, a belt system would be perfect for multiple motors. As has been mentioned, using a centrifugal supercharger removes all the question about the reliability issues of my purposed gear setup which has obvious long term use concerns.

So, Ill run the kit as intended for a year or so, then start back up trying to electrify it. In the mean time, I'm still going to be active here and do what I can to help. I want to see this succeed. I will probably still try to develop my control system in the case someone else wants to use it. Hopefully that will start beginning of next year. Ive picked up a couple microcontrollers which may make it pretty exciting.

[neutron256]

Originally Posted by rusty959

So just to give an update on what ive been doing, the short answer is not much. Mostly this is due to buying a house as Ive stated a few times, but more so Ive really been thinking about the feasibility and point of going e-supercharger.

One of the main reasons I wanted to do this and do it big was the ability to decouple the boost from engine RPM. Obviously I had plans from the start to be able to highly tune what boost I wanted where. However, I didn't realize how bad high boost at low rpms was for an engine. Obviously, tune makes a difference, and building the engine will resolve it from being an issue, but if without opening up the block I can't run uber boost at low rpms, Ive lost part of the reason I wanted to do this.

My second issue creeping up is I will be leaving in June for some military training that will last about a year. While I am convinced that a setup such as what Neutron is doing or the phantom setup can run reliably, my proposed system can't. While a little bit of upkeep is fine, even to the point of changing out gears, the system as a whole probably wouldn't be ironed out in 6 months, and Ill need a reasonably reliable car through that year.

My current tentative plan moving forward is the Kraftwerks rotrex kit, for a couple reasons. One of the most important reasons for this thread is that it has a second belt system, offset from the factory one. This will make a perfect start to not use the crank pulley and fab up a couple electric motor mounts. Especially considering these brushless motors can run either direction with no issues, a belt system would be perfect for multiple motors. As has been mentioned, using a centrifugal supercharger removes all the question about the reliability issues of my purposed gear setup which has obvious long term use concerns.

So, Ill run the kit as intended for a year or so, then start back up trying to electrify it. In the mean time, I'm still going to be active here and do what I can to help. I want to see this succeed. I will probably still try to develop my control system in the case someone else wants to use it. Hopefully that will start beginning of next year. Ive picked up a couple microcontrollers which may make it pretty exciting.

I like the Rotrex planetary roller system. It seems well suited for the levels of boost you're looking to get. Do you know what the input/output ratios are? It seems like you might be better looking into small EV brushless motors for it considering the input RPM will be relatively very low compared to a direct drive system.

[rusty959]

For the unit that comes with the rotrex kit there is a 9.49 ratio. So, a little over 10.5k shaft rpm to hit its 100krpm max impeller speed.

Yes it is a little low in comparison, but there are still rc caliber motors that will work well in that range without too much gearing. Even if I have to gear it from say 20k down to 10, thats not bad. I haven't looked into it but I feel anything EV related will be significantly more expensive. But, I could be wrong.
There is a pretty good supply of sub 200kv brushless motors designed to replace small (50-150 cc) gas motors for various r/c aircraft.

http://www.rotrex.com/Home/Technology/Product_Overview

[wulfgang]

If you get the Rotrex unit, you could ditch those R/C motors and go with an EV motor, which can give you better reliability and of course a whole lotta powah! I guess they aren't cheap, though

[rusty959]

Originally Posted by wulfgang

If you get the Rotrex unit, you could ditch those R/C motors and go with an EV motor, which can give you better reliability and of course a whole lotta powah! I guess they aren't cheap, though

Ive been looking at them a bit. Thing is, to get something of the power I would need it is significantly larger, more expensive, and uglier than a couple brushless rc motors.

Also, I'm not really needing the reliability of a EV motor. The duty cycle is quite low for a setup like this. It will run hard for maybe 10 seconds tops, then have some rest time. On an autocross track it will run hard for maybe 3 seconds, then every 10 seconds have a couple seconds of running hard. Or at least that is the case with the tracks I typically run on.

Beyond that, it isn't like these r/c motors have bad reliability. The motors themselves are pretty simple. The way they are built the only things that can really wear out are the bearings. They don't have brushes or communicator like a traditional DC motor. As long as you don't overheat them there isn't much to worry about.

[neutron256]

I've been doing some test fitting today. The small T4 compressor fits nicely. Fitting a larger compressor will be tricky.




Next will be fitting the charger. I have parts on order for that.

[rusty959]

Originally Posted by neutron256

I've been doing some test fitting today. The small T4 compressor fits nicely. Fitting a larger compressor will be tricky.




Next will be fitting the charger. I have parts on order for that.

What are you doing for power? I feel like somewhere I remember hearing you were going to start with 12v but you wouldn't need a charger for that.

[neutron256]

Originally Posted by rusty959

What are you doing for power? I feel like somewhere I remember hearing you were going to start with 12v but you wouldn't need a charger for that.

I'm going to be using the marine charger I posted about earlier. It will work for a 12v or 24v setup. I want this system to be as flexible as possible so I can test a varsity of compressors and motors.

[rusty959]

Originally Posted by neutron256

I'm going to be using the marine charger I posted about earlier. It will work for a 12v or 24v setup. I want this system to be as flexible as possible so I can test a varsity of compressors and motors.

So are you starting with a 12V setup and just using a separate battery charged by that charger or 24v? I was under the impression you were going to begin with 12v ran strait off the battery to simplify things to start.

[neutron256]

Originally Posted by rusty959

So are you starting with a 12V setup and just using a separate battery charged by that charger or 24v? I was under the impression you were going to begin with 12v ran strait off the battery to simplify things to start.

Nope I was always going to be using a secondary battery. With the Minn Kota charger I found I've decided to go ahead and test both 12v and 24v to see what kind of performance difference there is. I currently Have three Odyssey P680s ready to go for a 12v/24v setup.

I should be getting the parts tomorrow to start building the mount for the charger, and batteries. Once that's done and installed I'll need to get back to designing my controller.

[neutron256]

So not a terribly exciting update, but here is my weekend project.

Making mounting brackets for the Minn Kota charger. It's a simple bracket spanned between the firewall braces. I just used some 1" right angle aluminum channel, and 7/8" P-clamps.

The next step will be to make a plate to hold the batteries in the existing battery tray and route/connect the wiring to the charger.

[Luckrider]

It's the weekend! I want an update