Open Source Electric Supercharger

[neutron256]

Originally Posted by Luckrider

It's the weekend! I want an update

Sorry but not much exciting from me this weekend. Winter has made a sudden appearance here so now for now I'm just working on designing my controller.

[Luckrider]

Totally understandable. I have been trying to find out more about the specifics of the Phantom setup to see how it can be improved. My biggest gripe about it is that it does not make enough boost. While it does work within the safety limits of the ECUs programming, it fails to take full advantage of the benefits this design has to offer.

Have you considered the Phantom control module, or does it not have the necessary adjustments to work with the greater capacity of the compressor and motor you have chosen?

[neutron256]

Originally Posted by Luckrider

Totally understandable. I have been trying to find out more about the specifics of the Phantom setup to see how it can be improved. My biggest gripe about it is that it does not make enough boost. While it does work within the safety limits of the ECUs programming, it fails to take full advantage of the benefits this design has to offer.

Have you considered the Phantom control module, or does it not have the necessary adjustments to work with the greater capacity of the compressor and motor you have chosen?

I will say that Rob has done a tremendous amount of experimentation and testing with the Phantom design and I honestly don't expect I will see as much boost as he's getting. He's doing a lot of design and custom machining like fitting larger then standard compressor wheels to small housings.

My design is all about being low cost (somewhat), easy to build, and very very flexible. It's more of an experimentation platform then something intended to achieve peek performance. It will support a variety com compressor sizes, motors, and voltages. Even my controller should be fairly easy to assemble by someone with some basic electronics/soldering experience.

If you really want more boost I think you'll probably need to look into higher voltages and/or a geared system that will allow for higher compressor speeds.

Sadly with winter here I probably won't be doing much if any actual testing until spring. Lots of low end torque doesn't seem like a great idea on snow and ice covered roads.

[Luckrider]

His motor doesn't look as large as yours. I am not sure if that is an important factor, but I would like the compressor to spool up a little more and I don't know if just more juice can do that, and the controller treats excess voltage as bad and trips the failsafe.

[neutron256]

Originally Posted by Luckrider

His motor doesn't look as large as yours. I am not sure if that is an important factor, but I would like the compressor to spool up a little more and I don't know if just more juice can do that, and the controller treats excess voltage as bad and trips the failsafe.

I feel like there is some joke there about the size of your motor.

There is a balance between motor size and speed. Bigger motors have lower max RPMs, while smaller motors can have some crazy high RPMs but won't have the power to actually turn that fast under load. I have a range of motors that I'll be experimenting with to try and find the right balance. Also compressor size comes into play.

[mr. snodgrass]

A few things to ponder in order of difficulty to test:

1. Using a compressor intake restrictor
2. Big compressor wheels in modified compressor housing
3. Vaned diffuser
4. Simple roller gear train for impeller input shaft

tldr;

Reduce the diameter on the compressor intake to "mock" a smaller inducer and get more acceleration in the wheel. I think this will increase the PR at low flow rates. NB. will cause choking at higher flow rates. Mostly speculative, probably not worth it for small compressors. Some info is floating around for WRC cars, where a restrictor is a requirement.

Put the biggest wheel you can in your compressor housing. If you can find one, choose a wheel with less sweep on the exducer edge, since this will increase the tip exit velocity. The reason they're swept back is to reduce wake at moderate to high flow rates -- but we are no where near that.

Reduce the compressor volute by filling with epoxy and machining out new volute (be creative). Should boost pressure in low-flow applications, but will act as restriction at high flow rates (for that compressor).

Add a little bit of an internal tongue diffuser, see:

https://data.epo.org/publication-ser.../document.html

Add diffuser fins to the back plate. Should benefit flow in this application since we have tight control of the compressor speed (unlike an exhaust driven turbo). Getting the angle right might be tricky, but there's plenty of math around to allow you to calculate the angle for a given (target) flow rate.

The rotrex epicyclical super-charger transmission is a thing of beauty. But what about just trying a conventional single stage reduction gear train using bicycle hubs and steel roller gears under heavy load?

=======================================

Compressor intake restrictors:

The WRC dictated that intake restrictors be used on competing cars. Kinna sucks, since it limits the top output... but it also has interesting (read good) effects at lower flow rates:

http://www.rallyandracing.biz/air-in...-n.html?lang=1

I figure if you go for an oversized compressor in the 500HP+ category, then restricting its 4 inch intake to 3 or even 2.5 inches is going to be no big deal. I reckon it's worth a go for anyone who's building.

=======================================

Big compressor wheels in modified housings

Have a look at the compressor map for the Paxton N2500:

http://www.stangtv.com/tech-stories/...werhat-review/

It maps a PR of ~1.2 at around 20k rpm and 60 CFM. In other words it's in the ball park for a BLDC direct drive that can make sufficient torque. It uses a dinner-plate for the impeller (the inducer is 94mm!).

But back in the real world you'll see a trend towards useable boost at lower compressor speeds (36K rpm for the T76) with increasing impeller exducer diameter. There's a catch. The boost is at flow rates, which would equate to around 200 HP. In other words, you could use it if you're already making 200+ HP!

But all is not lost (I think). If you can make your compressors internal volume (volute) "smaller"... Given that we're operating at relatively low pressures, temperatures, and flow rates within the compressor. I reckon a cut and shut job of the housing might be a goer. Even something as simple as filling the volute with an epoxy and chipping out a new smaller volute might work. I reduced volute should boost pressure in low-flow applications, but will act as restriction at high flow rates (for that compressor).

The best I can think of is to buy a cheap chinese "T76" fake from flea-bay and modifying the compressor intake, diffuser, and internal volute so that it is optimised for low flow rates and pressures.

Optimising this a step further leads to...

=======================================

Backplate Vaned Diffuser :

Google up "centrifugal compressor diffuser" and go to the images tag. You should see some pictures of vaned diffuser plates. Their purpose is to prevent the wake from the exducer blade tips from screwing up the high-speed/low-pressure to low-speed/high-pressure conversion that happens across the diffuser plate and to guide the flow angle as it enters the volute. They're not present in modern automotive compressors since the vane angle needs to change depending on flow rate. However, we're different since the BLDC drive restricts us to a low PR and quite low flow rates (for the compressor). +10 to anyone who implements variable vane control ;-)

=======================================

A roller gear train for the impeller shaft.

This one is hard. Rotrex has some beautiful supercharger transmissions. If you hunt you can find pictures of the internals on the internet. We (enthusiasts) can't do anything like a Rotrex (240,000 rpm!), but maybe we can get to 60,000 rpm?? using conventional roller gears.

Rotrex uses steel (?) planet gears in it's transmissions together with some funky self adjusting tensioners and secret "traction oil" to counteract the loss of traction at high speed.

Now the steel roller gears sound like a good idea to me. Given enough load (think locomotive) smooth steel wheels can hall hundreds of tonnes without slipping and with the lowest possible rolling resistance. But there is a challenge here ==> the loading requirements.

To make a single reduction gear train you will need to apply a large (20 kg+ ?) to the wheel-on-wheel surface. This load would be way too much for the puny little motors and impeller spindles.

The proper approach would involve lots of machine-shop work and expensive bits. But what if we used everyday axles designed to take heavish loads? The only thing I could think of was bicycle hubs. They're cheap, plentiful, and able to take 50kg + each.

I'm sorry I don't have any diagrams.

Imagine the impeller axle being supported by the rear bike hub (the axle moves in the hub and the is clamped)

The BLDC shaft would be connected through a polyprop-damped coupler to the front axle (hub also clamped).

Steel roller gears are mounted at the opposite ends of each of the axles.

They are made to engage under heavy load so that the gear train does not slip. The hubs should be able to easily carry this load. The gear train would hopefully be able to operate at high speed but this is asking a lot of bike bearings!

Ok. that's all i've got.. actually one more thing.

The Rotrex "traction oil". I reckon it might have the Post-It note low tack glue dissolved into the oil. Pure speculation.

[rusty959]

Tons of information there, and since it is your first post, welcome to the forum.

[mr. snodgrass]

Hi guys. Good news (I think).

I happened upon my Grandad's ancient hand bench grinder today. It has a built in 10 to 1 gearbox, and I reckon could be "adapted" for other applications...

Here's a photo of one (not mine) disassembled:



And here's a cut-away of the real-deal Vortex supercharger gearbox:






Now it might be a bit of a leap to turn a 60+ year old tool into a precision gear-box, but it might just be a goer for an output shaft speed in the 50k rpm mark.

BTW. there are plenty of cheap examples on ebay. Search for "antique bench grinder" or "hand bench grinder"

[Ingen]

Originally Posted by mr. snodgrass

Hi guys. Good news (I think).

I happened upon my Grandad's ancient hand bench grinder today. It has a built in 10 to 1 gearbox, and I reckon could be "adapted" for other applications...


Now it might be a bit of a leap to turn a 60+ year old tool into a precision gear-box, but it might just be a goer for an output shaft speed in the 50k rpm mark.

BTW. there are plenty of cheap examples on ebay. Search for "antique bench grinder" or "hand bench grinder"

If you have any sentimental attachment to your gearbox at all, definitely don't try this... And don't try it in the car until you bench test it lots.

My personal opinion is that the gears won't be balanced well enough, the bearings aren't ready for that rotation speed, and it will probably explode / grenade... But hey, try it Just not near your car or anything that can get dinged up.

[neutron256]

Originally Posted by Ingen

If you have any sentimental attachment to your gearbox at all, definitely don't try this... And don't try it in the car until you bench test it lots.

My personal opinion is that the gears won't be balanced well enough, the bearings aren't ready for that rotation speed, and it will probably explode / grenade... But hey, try it Just not near your car or anything that can get dinged up.

+1

This is not designed for the kind of speeds involved in an electric supercharger. In addition to the risk of catastrophic failure I suspect the effeiciency of this is relitivly low and turning big heavy gears would probably equal lots of lag both getting it up to speed and slowing it down.

Finding components that can handle this kind of speed 40K+ RPM is really hard. At those speeds balance becomes critical. Even finding bearings that run that fast are a fairly limited selection.

[neutron256]

Originally Posted by mr. snodgrass

A few things to ponder in order of difficulty to test:

1. Using a compressor intake restrictor
2. Big compressor wheels in modified compressor housing
3. Vaned diffuser
4. Simple roller gear train for impeller input shaft

tldr;

Reduce the diameter on the compressor intake to "mock" a smaller inducer and get more acceleration in the wheel. I think this will increase the PR at low flow rates. NB. will cause choking at higher flow rates. Mostly speculative, probably not worth it for small compressors. Some info is floating around for WRC cars, where a restrictor is a requirement.

Put the biggest wheel you can in your compressor housing. If you can find one, choose a wheel with less sweep on the exducer edge, since this will increase the tip exit velocity. The reason they're swept back is to reduce wake at moderate to high flow rates -- but we are no where near that.

Reduce the compressor volute by filling with epoxy and machining out new volute (be creative). Should boost pressure in low-flow applications, but will act as restriction at high flow rates (for that compressor).

Add a little bit of an internal tongue diffuser, see:

https://data.epo.org/publication-ser.../document.html

Add diffuser fins to the back plate. Should benefit flow in this application since we have tight control of the compressor speed (unlike an exhaust driven turbo). Getting the angle right might be tricky, but there's plenty of math around to allow you to calculate the angle for a given (target) flow rate.

The rotrex epicyclical super-charger transmission is a thing of beauty. But what about just trying a conventional single stage reduction gear train using bicycle hubs and steel roller gears under heavy load?

=======================================

Compressor intake restrictors:

The WRC dictated that intake restrictors be used on competing cars. Kinna sucks, since it limits the top output... but it also has interesting (read good) effects at lower flow rates:

http://www.rallyandracing.biz/air-in...-n.html?lang=1

I figure if you go for an oversized compressor in the 500HP+ category, then restricting its 4 inch intake to 3 or even 2.5 inches is going to be no big deal. I reckon it's worth a go for anyone who's building.

=======================================

Big compressor wheels in modified housings

Have a look at the compressor map for the Paxton N2500:

http://www.stangtv.com/tech-stories/...werhat-review/

It maps a PR of ~1.2 at around 20k rpm and 60 CFM. In other words it's in the ball park for a BLDC direct drive that can make sufficient torque. It uses a dinner-plate for the impeller (the inducer is 94mm!).

But back in the real world you'll see a trend towards useable boost at lower compressor speeds (36K rpm for the T76) with increasing impeller exducer diameter. There's a catch. The boost is at flow rates, which would equate to around 200 HP. In other words, you could use it if you're already making 200+ HP!

But all is not lost (I think). If you can make your compressors internal volume (volute) "smaller"... Given that we're operating at relatively low pressures, temperatures, and flow rates within the compressor. I reckon a cut and shut job of the housing might be a goer. Even something as simple as filling the volute with an epoxy and chipping out a new smaller volute might work. I reduced volute should boost pressure in low-flow applications, but will act as restriction at high flow rates (for that compressor).

The best I can think of is to buy a cheap chinese "T76" fake from flea-bay and modifying the compressor intake, diffuser, and internal volute so that it is optimised for low flow rates and pressures.

Optimising this a step further leads to...

=======================================

Backplate Vaned Diffuser :

Google up "centrifugal compressor diffuser" and go to the images tag. You should see some pictures of vaned diffuser plates. Their purpose is to prevent the wake from the exducer blade tips from screwing up the high-speed/low-pressure to low-speed/high-pressure conversion that happens across the diffuser plate and to guide the flow angle as it enters the volute. They're not present in modern automotive compressors since the vane angle needs to change depending on flow rate. However, we're different since the BLDC drive restricts us to a low PR and quite low flow rates (for the compressor). +10 to anyone who implements variable vane control ;-)

=======================================

A roller gear train for the impeller shaft.

This one is hard. Rotrex has some beautiful supercharger transmissions. If you hunt you can find pictures of the internals on the internet. We (enthusiasts) can't do anything like a Rotrex (240,000 rpm!), but maybe we can get to 60,000 rpm?? using conventional roller gears.

Rotrex uses steel (?) planet gears in it's transmissions together with some funky self adjusting tensioners and secret "traction oil" to counteract the loss of traction at high speed.

Now the steel roller gears sound like a good idea to me. Given enough load (think locomotive) smooth steel wheels can hall hundreds of tonnes without slipping and with the lowest possible rolling resistance. But there is a challenge here ==> the loading requirements.

To make a single reduction gear train you will need to apply a large (20 kg+ ?) to the wheel-on-wheel surface. This load would be way too much for the puny little motors and impeller spindles.

The proper approach would involve lots of machine-shop work and expensive bits. But what if we used everyday axles designed to take heavish loads? The only thing I could think of was bicycle hubs. They're cheap, plentiful, and able to take 50kg + each.

I'm sorry I don't have any diagrams.

Imagine the impeller axle being supported by the rear bike hub (the axle moves in the hub and the is clamped)

The BLDC shaft would be connected through a polyprop-damped coupler to the front axle (hub also clamped).

Steel roller gears are mounted at the opposite ends of each of the axles.

They are made to engage under heavy load so that the gear train does not slip. The hubs should be able to easily carry this load. The gear train would hopefully be able to operate at high speed but this is asking a lot of bike bearings!

Ok. that's all i've got.. actually one more thing.

The Rotrex "traction oil". I reckon it might have the Post-It note low tack glue dissolved into the oil. Pure speculation.

All intresting ideas, although my personal goal is to just get a basic working prototype first.

[kj2229]

i am korean...so i'm not good at english.
i made 6type e-superchargers during 2 years.
my car is not ft86....but it's not problem.
i made e-superchargers at my benz c300 4matic(2008)....
finally say....i think...e-superchar is very funny item.

below potho is making twin e-superchargers last summmer..


now.. ihave twin e- supercarger.....but turbine is not twin...because of space.
one is td05 20g...and the other is nissan gtr34 stock turbine.

i will upload pothos later..

[rusty959]

Originally Posted by kj2229

i am korean...so i'm not good at english.
i made 6type e-superchargers during 2 years.
my car is not ft86....but it's not problem.
i made e-superchargers at my benz c300 4matic(2008)....
finally say....i think...e-superchar is very funny item.

below potho is making twin e-superchargers last summmer..


now.. ihave twin e- supercarger.....but turbine is not twin...because of space.
one is td05 20g...and the other is nissan gtr34 stock turbine.

i will upload pothos later..

Sounds very interesting. What were you powering them with? How well did it work?
@neutron256 any updates or has your winter been unproductive like mine?

[neutron256]

Originally Posted by rusty959

Sounds very interesting. What were you powering them with? How well did it work?
@neutron256 any updates or has your winter been unproductive like mine?

I've gotten some done but nothing much to show. I'm just working the the electronics for the control module. I think once the snow melts I'll have a working prototype ready to bolt on and test.