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Forced Induction Turbo, Supercharger, Methanol, Nitrous


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Old 06-25-2014, 07:48 PM   #687
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Working on my control system. I tried designing my own controller with limited success. I was just having too much trouble getting the signaling right. So I'm back to using the Unichip as a controller for the compressor motor.

Every thing is wired up right, and I can hook a servo up and control it just fine, but for some reason the Turnigy Fatboy V2 ESC I'm using doesn't like the servo signal from the Unichip.

Any RC experts out there have any ideas as to what might be going on? It works just fine when I hook it up to a servo tester.
I would say take baby steps. Dialing down the feedback control will need a thorough rework should you change your motor, compressor or ESC.

I would recommend running the system in open loop (pretty much like Phantom), see what range of boost you are working with, and then try to may be optimize it in a closed loop. Your thoughts ?

Any news from the tuning front? I would say Shiv's tuning tables from the Phantom setup could be a good starting point.

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Old 06-25-2014, 08:49 PM   #688
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Working on my control system. I tried designing my own controller with limited success. I was just having too much trouble getting the signaling right. So I'm back to using the Unichip as a controller for the compressor motor.

Every thing is wired up right, and I can hook a servo up and control it just fine, but for some reason the Turnigy Fatboy V2 ESC I'm using doesn't like the servo signal from the Unichip.

Any RC experts out there have any ideas as to what might be going on? It works just fine when I hook it up to a servo tester.
If you give more detail on what you were doing, how and what it was hooked up to, and what exactly it was doing I can help. I have some experience controlling a ESC from a microcontroller. Have an oscilloscope? That can help too.
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Old 06-25-2014, 09:45 PM   #689
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If you give more detail on what you were doing, how and what it was hooked up to, and what exactly it was doing I can help. I have some experience controlling a ESC from a microcontroller. Have an oscilloscope? That can help too.
I'm running a duty cycle signal at 50hz from the Unichip to the ESC. 5% -10% Duty cycle (1-2 ms on ). This should be about the ideal servo signal. If I connect a servo to the Unichip instead of the the ESC it controls it perfectly. When I connect a server test box to the ESC it will drive the motor just fine.

For some reason the ESC doesn't like the signal from the Unichip. One thing I noticed when controlling the ESC with the servo tester is that it sometimes but not always seems to have a boot up delay with a beep the first time I speed it up after its powered on.
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Old 06-25-2014, 10:29 PM   #690
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I'm running a duty cycle signal at 50hz from the Unichip to the ESC. 5% -10% Duty cycle (1-2 ms on ). This should be about the ideal servo signal. If I connect a servo to the Unichip instead of the the ESC it controls it perfectly. When I connect a server test box to the ESC it will drive the motor just fine.

For some reason the ESC doesn't like the signal from the Unichip. One thing I noticed when controlling the ESC with the servo tester is that it sometimes but not always seems to have a boot up delay with a beep the first time I speed it up after its powered on.
My best two recommendations are 1) getting it on a oscilloscope to see what the signal is actually doing and 2) using a buffer to make sure the signal is clean and the proper voltage. #1 is probably going to be the best thing. The signal is likely just doing something weird that the servo is able to compensate for or just not care about while the ESC gets pissed over. Without seeing the signal you don't really know what its doing for sure.
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Old 06-25-2014, 10:52 PM   #691
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My best two recommendations are 1) getting it on a oscilloscope to see what the signal is actually doing and 2) using a buffer to make sure the signal is clean and the proper voltage. #1 is probably going to be the best thing. The signal is likely just doing something weird that the servo is able to compensate for or just not care about while the ESC gets pissed over. Without seeing the signal you don't really know what its doing for sure.
I already checked it on an oscilloscope. It's just as I would want to see 50hz, 1-2ms on time. I think it's something to do with the ESCs startup. I'm going to try a different motor and if that doesn't work a different motor and ESC.
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Old 06-26-2014, 11:09 AM   #692
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Okay so good news is my Unichip control system seems to be working perfectly as is the Fatboy V2 ESC. The problem is that the AquaStar T20 motor seems to have developed an intermittent problem with one of its connectors. It's a neat motor, but I have no love for it's complex wiring setup.

So now I need a new motor, I already had one on order, but it's coming from china so it won't be here for a week or so.

SkyRC Beast X513 3Y
http://www.skyrc.com/index.php?route...product_id=145

It's less powerful, but I wanted to see how it will work.

Assuming it's not powerful enough I'm going to need a heftier motor. TP Power is looking like a great candidate. Thanks @AN
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Old 06-26-2014, 11:26 AM   #693
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Here is my favored motor so far for my 24V system. It's 1440kv 3850W continuous output, and it has the needed 8mm shaft. At a peak voltage that would give 41K RPM.

TP Power: TP 4070 3Y

http://www.tppowerusa.com/motors/in-...ame&order=DESC
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Old 06-26-2014, 12:35 PM   #694
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Here is my favored motor so far for my 24V system. It's 1440kv 3850W continuous output, and it has the needed 8mm shaft. At a peak voltage that would give 41K RPM.

TP Power: TP 4070 3Y

http://www.tppowerusa.com/motors/in-...ame&order=DESC
I have been doing some reading about the actual peak voltage you will see from the Lead Acid Battery while on a reasonable (large than reasonable in our case) load on the motor. You will not even see 24v across your battery pack while boosting. In other words, you will not see 41k rpm with a 1440 KV motor. I would recommend you get a higher KV model to get maximum possible motor RPMs from the 24v setup.

My recommendation would be the 5650 -6D 1800 KV motor. Its a 56mm Motor, more tq, 4200W Continuous power, 50k rpm max rpm.

This motor should rev up to 43k rpm on a 24v pack easily. You are not pushing it too much as far as peak V goes. And remember, this motor will only need more current if it sees more load. So in your setup, it should have no problem giving max possible boost low down the engine rpm. As Engine revs higher, the motor will need more current to keep the boost up. I guess you will reach the battery current capacity at high engine rpm. Then you can start looking at integrating your BoostCaps .



btw, its a build your own motor so I suspect some build time on it. They might even work with you on the kind of shaft you need for this.
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Old 06-26-2014, 08:04 PM   #695
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I already checked it on an oscilloscope. It's just as I would want to see 50hz, 1-2ms on time. I think it's something to do with the ESCs startup. I'm going to try a different motor and if that doesn't work a different motor and ESC.

Fair enough. Probably the only other big thing I can think of is I know one of my ESC's required the throttle to be at 0% for a certain amount of time before it would enable.
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Old 06-27-2014, 01:29 PM   #696
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Okay ... Friday is a slow day at work ... so I started spending more time with Airflow calculations. If you are able to spin the Seadoo 215 compressor at 43k RPM, you can move 20 lb/s of air. (assuming at sea level). 20 lb/s should give you a pretty healthy boost. Per my calculations, as much as 12 psi @ 4500 rpm (not likely due to compressor surge line), tapering off to just under 3psi @ 7500 rpm. matrix below.

This sounds really good, may be too good to be true. In my opinion, limiting factor here would be:

Battery Current available for the TP Motor.
Compressor Surge line at lower engine rpms.

BTW @ Neutron256, If you are getting the TP Motor and haven't yet ordered it, I would recommend the 5840S-6D (Link) over 5650-6D. They both have exactly same specs (Power, Peak V, Peak I, Max RPM, KV). However, the 5840S seams to have heat dissipation grooves etc.
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Old 06-27-2014, 01:36 PM   #697
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Okay ... Friday is a slow day at work ... so I started spending more time with Airflow calculations. If you are able to spin the Seadoo 215 compressor at 43k RPM, you can move 20 lb/s of air. (assuming at sea level). 20 lb/s should give you a pretty healthy boost. Per my calculations, as much as 12 psi @ 4500 rpm (not likely due to compressor surge line), tapering off to just under 3psi @ 7500 rpm. matrix below.

This sounds really good, may be too good to be true. In my opinion, limiting factor here would be:

Battery Current available for the TP Motor.
Compressor Surge line at lower engine rpms.

BTW @ Neutron256, If you are getting the TP Motor and haven't yet ordered it, I would recommend the 5840S-6D (Link) over 5650-6D. They both have exactly same specs (Power, Peak V, Peak I, Max RPM, KV). However, the 5840S seams to have heat dissipation grooves etc.
Nice work. It all looks promising. I did already order the TP 4070 3Y from TP Power. I agree with you that the voltage drop under load will limit the max RPM but I figure that motor is a good safe starting point, and if I find I'm not getting the performance I want I have no problem ordering a higher KV motor.

The new motor should be here Monday. It looks like they use a 6 hole mounting pattern so I will have to adapt the compressor which is currently setup for a 4 hole mount.
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Old 06-27-2014, 01:52 PM   #698
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Nice work. It all looks promising. I did already order the TP 4070 3Y from TP Power. I agree with you that the voltage drop under load will limit the max RPM but I figure that motor is a good safe starting point, and if I find I'm not getting the performance I want I have no problem ordering a higher KV motor.

The new motor should be here Monday. It looks like they use a 6 hole mounting pattern so I will have to adapt the compressor which is currently setup for a 4 hole mount.
Kool .. Looks like time for a new spacer ... w/o the extra hole.
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Old 06-27-2014, 01:59 PM   #699
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@neutron256 Also, about the Seadoo SC, that wheel looks really heavy, the blades are really thick (did you notice that too) ... I tried to do some reading online and concluded that since water-crafts hop over waves while in full throttle, their engines go thru very extreme rpm fluctuations ... impellers are not able to keep up with such fluctuations. As a result, they had to introduce a clutch assembly to the supercharger drive so that the impeller can 'slip' during such fluctuations. For the impeller to maintain its rpm during fluctuations, they had to give it more weight/momentum so that it can 'slip' well.

Do you see this helping/hurting this application ? Does a heavy impeller translate into a less responsive engagement. Also, a heavy impeller means bigger current draw while the impeller accelerates to its peak rpm. Your thoughts ?
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Old 06-27-2014, 02:08 PM   #700
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@neutron256 Also, about the Seadoo SC, that wheel looks really heavy, the blades are really thick (did you notice that too) ... I tried to do some reading online and concluded that since water-crafts hop over waves while in full throttle, their engines go thru very extreme rpm fluctuations ... impellers are not able to keep up with such fluctuations. As a result, they had to introduce a clutch assembly to the supercharger drive so that the impeller can 'slip' during such fluctuations. For the impeller to maintain its rpm during fluctuations, they had to give it more weight/momentum so that it can 'slip' well.

Do you see this helping/hurting this application ? Does a heavy impeller translate into a less responsive engagement. Also, a heavy impeller means bigger current draw while the impeller accelerates to its peak rpm. Your thoughts ?
Yeah the clutch system is interesting. It is a heavy wheel but from my testing with the Aqustar motor it has no problem getting it up to speed or slowing it down. Remember one of the big advantages of electric motors is that the pretty much have full torque from a dead stop.

This can also be addressed with a programmable ESC that supports soft starts and breaking, as well as governing which works to maintains constant speed under shifting loads. The Fatboy V2 ESC I'm using has all these features.
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