Open Source Electric Supercharger

[litemup]

Yeah but listening to the bench test you did with the smaller motor, you were well past that frequency without exciting any modes.

Instability can be a tough thing to chase. The whole system must be taken into account and may even be brought out by how it is mounted.

I think you have a long cantilevered mass in that motor which is hard-mounted to the housing. I can see why you were forced to mill down the ribs in the housing but they existed primarily to prevent this very thing. Not a showstopper but essential to consider while moving forward.

[litemup]

Originally Posted by neutron256

Very useful. What software are you using to do the analysis?

Whoops - damn it! Keep forgetting to quote.

http://audacity.sourceforge.net

[neutron256]

Originally Posted by litemup

Yeah but listening to the bench test you did with the smaller motor, you were well past that frequency without exciting any modes.

Instability can be a tough thing to chase. The whole system must be taken into account and may even be brought out by how it is mounted.

I think you have a long cantilevered mass in that motor which is hard-mounted to the housing. I can see why you were forced to mill down the ribs in the housing but they existed primarily to prevent this very thing. Not a showstopper but essential to consider while moving forward.

It's hard to know but I suspect that the reason it wasn't showing as much audible vibration with the smaller motor (with 6mm shaft) is because the shaft was flexing and absorbing some of the vibration. It also didn't have the housing together so that may have had some effect as well.

Because with the smaller motor and the housing assembled the impeller flexed and contacted the housing above a given speed we know there was still imbalance. It's also possible that additional imbalance was introduced to the wheel after contacting the housing during testing even though there didn't appear to be any visible damage the the impeller.

Regardless running this size of impeller has it's advantages, but also has it's drawbacks. It's all an experiment. And if it fails, then this data will give a good clue to why.

[litemup]

Originally Posted by neutron256

Regardless running this size of impeller has it's advantages, but also has it's drawbacks. It's all an experiment. And if it fails, then this data will give a good clue to why.

I'm just stoked. ...and am ready to hit the u-pull-it to find some kind of turbo I can cut up. No practical experience with FI yet but what the hell. I have enough hubris to make up for it.

[neutron256]

I just want to say I love all the interest and suggestions. I love this sort of crowd sourcing of ideas and It's helped me learn a lot.

As I'm waiting on parts I've been rethinking my system for coupling the motor to the Impeller. I really like the propeller adapter collets, but I'd like to shorten the overall length. Right now I'm looking at machining a taper into the the bottom of the impeller for the collet. A shorter shaft with less parts equals a lighter stronger shaft. I need to consult my expert machinist to see how doable this is.

Keep the ideas coming guys I'm I can't test them all but if I can I'll test the best most practical ones.

[neutron256]

I spent a bunch of time this weekend testing and working on the SeaDoo supercharger setup. It's not going well, no matter what I do I just can't seem to get smooth consistent activation. I've tried a few different motors, and different settings on the controller. I think the impeller wheel may just be too massive for a motor that can achieve the desired RPMs.

I've been checking out RC forums a lot and it seems like one solution may be to go with a sensored motor rather than the sensorless motors I have been using. Apparently sensored motors have far less issues with cogging, and much smoother activation. The problem is that I have yet to find a large/fast enough sensored motor for this application. So if anyone comes across one let me know.

In the mean time I think I'm going to refocus on my smaller compressor design and getting that ready to test. The motor is special order from china, but should get here in the next week or so. In the mean time I've ordered the tooling for machining a taper into the impeller to directly fit the collet adapter. This will make a clean fit with a short and stronger shaft.

[AN]

Originally Posted by neutron256

In the mean time I think I'm going to refocus on my smaller compressor design and getting that ready to test. The motor is special order from china, but should get here in the next week or so. In the mean time I've ordered the tooling for machining a taper into the impeller to directly fit the collet adapter. This will make a clean fit with a short and stronger shaft.

Sorry to hear the Seadoo didnt work out ... I had high hopes ...
So what motor / impeller/compressor housing are you going with now ? 5mm shaft or 8mm shaft ?

Having read up on a lot of compressor graphs, a T70 or a T72 compressor wheel with upwards of 92mm outer diameter will give you good boost at 40k rpm.

Please take a look at maps on this page :http://www.nwbombers.com/forums/topi...map-questions/

Notice the wheel specs on the maps. Most turbos selling on ebay had smaller wheels but i did find a few that have the larger wheels. A couple of examples are:

http://www.ebay.com/itm/171230678053...84.m1436.l2649

http://www.ebay.com/itm/130543950292...84.m1436.l2649

http://www.ebay.com/itm/221478464175...84.m1436.l2649

Also, you want to make sure the compressor A/R is as small as possible ... for low flow / low+early boost , these will work best.

These wheels have a shaft diameter or 7.9mm. Will that make it easier to couple a 5mm shaft motor in your opinion ?

[neutron256]

Originally Posted by AN

Sorry to hear the Seadoo didnt work out ... I had high hopes ...
So what motor / impeller/compressor housing are you going with now ? 5mm shaft or 8mm shaft ?

Having read up on a lot of compressor graphs, a T70 or a T72 compressor wheel with upwards of 92mm outer diameter will give you good boost at 40k rpm.

Please take a look at maps on this page :http://www.nwbombers.com/forums/topi...map-questions/

Notice the wheel specs on the maps. Most turbos selling on ebay had smaller wheels but i did find a few that have the larger wheels. A couple of examples are:

http://www.ebay.com/itm/171230678053...84.m1436.l2649

http://www.ebay.com/itm/130543950292...84.m1436.l2649

http://www.ebay.com/itm/221478464175...84.m1436.l2649

Also, you want to make sure the compressor A/R is as small as possible ... for low flow / low+early boost , these will work best.

These wheels have a shaft diameter or 7.9mm. Will that make it easier to couple a 5mm shaft motor in your opinion ?

I haven't completely given up on the SeaDoo compressor, but I'm stepping back a bit for now while I rethink and research.

For now I'm going small. I want to see if this can work with a small compressor and 12V dump pack. A bare bones system of sorts. T3 compressor with I think a .50 a/r. I already have a slight damaged one that it can use for bench testing.

The motor I order is a TP Power 4040 3D with a 5mm shaft.

4790kv
Max Amps: 350
Max Volts: 12V
Continuous Power: 1650W
Max Power: 4200W

Garrett impeller wheels actually all have a 1/4" shaft. I think the 7.9mm is probably the journal bearing portion of the shaft.

[neutron256]

Another update, I got some advice from an RC expert who suggested some changes to my speed controller settings (timing, current sensitivity, break, low voltage cutoff). It worked, and I'm getting much better control of the SeaDoo compressor. It's still very finicky though and doesn't like fast starts/changes, and cuts off before reaching full throttle.

[jwestra]

A simple 12V system would be great for boosting the lower RPM's on so many cars, if it works out. Thank you for doing all this research in such an open environment!
Any guesstimation how much less power the motor will generate?

[neutron256]

Originally Posted by jwestra

A simple 12V system would be great for boosting the lower RPM's on so many cars, if it works out. Thank you for doing all this research in such an open environment!
Any guesstimation how much less power the motor will generate?

It's really hard to say. The motor I'm testing first is capable of 4200W peek power so that would potentially put it on par with he Phantom Electric Supercharger, but I'm really not expecting it to work as well.

I'm planing in getting into the shop sometime this week to do the machining on the compressor. I've already assembled and installed the 12V power system in the car. In theory the motor I ordered should get her sometime this week or early next week.

Even with very low boost I'm excited to see what a 12V system can do.

[SloS14]

I find your lack of updates disturbing.

[neutron256]

Originally Posted by SloS14

I find your lack of updates disturbing.

LOL

Sorry nothing going on at the moment. I'm waiting on my built to order motor from TP Power. I emailed them earlier this week. Apparently it's been delayed due to weather in China. It should be arriving here in the states today an be shipped out to me ASAP.

Once I've got the motor I'll need to do some bench testing to determine if a 12V system can actually spin the small impeller smoothly.

[neutron256]

Sorry I haven't given any updates recently. A combination of waiting for parts and just taking a break lead to not much progress. Today however I made it to the shop and finished the machining on my small 12V compressor. Everything fits perfect and it's a solid setup.

I don't expect to get very much boost out of it at all. In fact if I can maintain positive pressure at redline I'll be happy. I'm using a sensored motor to help prevent cogging issues I've had with previous setups, and it should provide much smoother operation.




Next step will be lots of bench testing and building a control system.