VESC(ted) ESC trial

[maticulus]

I purchased the VESC version 2, 200A model last year because it was priced well for current level it could support and I wanted to keep the initial build low budget until I could produce results to justify using the "Money Hammer" on higher performing equipment. The motor is a TP 4070, 1400Kv, 75k rpm unit driven by 16s voltage with an ~1.8:1 belt drive.

Months passed before I finally decided to try setting everything up using the VESC, given how intimidating it appeared to be with all of the app functions and the poor detail provided on screen regarding what they do. Surprisingly it was easy to setup as far as demonstrating basic connectivity and signs of operation.

Performance is where the challenge came in. It was apparent to me that the compressor was not spinning up near max speed unloaded, ~ 40k rpm anticipated and instead was faulting out at 25k rpm after voltage, current and ERPM limits were corrected to get past the 20k rpm limit first encountered. There was also the matter of disabling braking as that could potentially result in loosening of the retaining nut and compressor wheel given the diameter relative to the shaft to wheel contact surface.

It's amazing how unhelpful most of the info I encountered was regarding how to disable braking. It's a straight forward question, but it yielded not one straightforward answer and I finally settled on setting motor current max brake, battery current max regen, and max ERPM reverse to nearly 0.

After giving it a lot of thought and noting that the same fault was repeatedly being set but varying depending no the rate of throttle input, I considered all things associated with current and noted that my experimental power supplying wires were probably only suitable for about 20 amps and a quick grab immediately following a motor cutout revealed both wires were hot to the touch through the insulation so I'll be switching them out for 8 awg.

I'm not sure how the VESC app calculates current but I put an ammeter in line and only measured about 60 amps at cutout. With what I was able to accomplish with the changes made in programming the blower sounds like it is performing as intended until it faults out.

I also discovered that I'll need to upgrade from the .5" belt to a 1" belt system. If the power wire upgrade does not eliminate the fault incidents I'll plan to retire the VESC and get a traditional non-complicated/over engineered ESC. Initially when I started working with it I noted that the motor was heating up seemingly quickly over brief runs that I did not observe with a small 80amp ESC in use. It appeared to work itself out as I adjusted parameters in the VESC app. I may dump it regardless because it is overly complicated for the job it is intended to do here.

 

[maticulus]

Upgraded the power wires to 8 gauge from what was probably 16 ga for testing and no improvement with the fault. In addition, I noted a problem I had not detected before but suspect it was present, when I touched the belt I noted a fine oscillation indicating the motor was not completely off and I suspect this contributed to the previous high motor temp observed despite light duty operation. This signals a wrap for the VESC, it's far more trouble than it's worth to me.

 

[wkerstens]

I really wanted the VESC solution to work, it looks great. Decent hardware, CAN communication, so many settings to play with, diagnostics etc etc. But after reading Alex his experiences and also the VESC forums it seems it simply not that stable yet, missing the basic features and not really suited to high e-rpm. Having designed motor controller myself in the past I was looking forward to playing with the VESC and tuning the motor step by step but I think I'll stick with the RC grade speed controllers for now. VESC is just not worth the trouble it seems.

 

[maticulus]

I've made some headway on moving towards my final concept. I watched the video of the 2535 on the dyno and noted the apparent limitation the designated ESC for the motor appeared to be. I called Castle and received permission to return the ESC in order to purchase the more powerful MAD MAX 21, 16S.

Then I thought that was "MAD" money to be spending on just one ESC as it's main benefit would be to push the motor into the danger zone contrary to reliability. I recalled Alex mentioning the possibility of an unlimited Cobra ESC possibly being made available and figured I'd keep what I have and order a second outfit instead considering it would be the same amount of money for just one MAD MAX 21.

Then I thought, with two motors there be no need to remove any safety features as I would sufficient safe power with everything in stock trim.
After watching a few RC cars with the 2535 blaze across turf at 90 mph, I decided to ditch the belt system. I didn't feel comfortable with the friction heat it developed with little load on the compressor. I'm using gears and will carve out the block sitting on top of hub and round it off as the motor mount/gear box with intentions of having it seal well enough to at least hold grease to keep the gears lubed or a heavy weight gear oil.

The real trick thing about this arrangement is that if it works as well as I believe it will, I could redesign the motor mount and add a 3rd motor in tripod configuration. My 1228 Lathe 8" 4 Jaw chuck was at its limit holding the 10" plate for the initial squaring and hub recess. I have to thread the plate for the retaining hub bolts and then chuck it up to marry the plate to the compressor housing which will also require a beveled lip for the V-band clamp. Once that's complete I'll work on the last part; the bearing races to hold the titanium shaft and then the shaft.

 

[maticulus]

Making progress. Initially running a 28:19-20 tooth ratio depending on which gear snugs up best. My 18 tooth is on the small side and although it engages both gears there would be too much backlash. I'm leaning toward the 20 tooth shaft gear being the perfect mesh and will pickup a pair of 30 tooth gears for the option to run 18-20 tooth shaft gears since the motor bolt holes will be slotted to allow outward adjustment.

After I put the motor mount block back in the vice and finish boring the remaining mount holes and then slot the motor mount holes, I'll be removing the vice from the mill table to make room for slotting the center hub to seat the motor mount block and drill and tap the receiver holes into the compressor hub. The shaft will be the last part made.

 

[AlexLTDLX]

Man, I need to check in here more often - that looks fantastic! I'm impressed. That setup should be able to run almost continuously.

 

[brettus8]

Might pay to get those gears closer in to the motor end bearing if at all possible ... shaft flex/bearing wear might become an issue. Use countersunk set screws perhaps?
Otherwise .... I'm seriously thinking about doing something similar for my build.

 

[maticulus]

Might pay to get those gears closer in to the motor end bearing if at all possible ... shaft flex/bearing wear might become an issue. Use countersunk set screws perhaps?
Otherwise .... I'm seriously thinking about doing something similar for my build.

I doubt it will be a problem at all considering the traditional loads the motor was designed for in a near 50lb rc car shock loading it from running over rough terrain will be absent, run time will pale in comparison and it's sharing a load with a like motor equating to a 50% reduction in load duty compared to being run by itself.

I'm favoring the compressor shaft over that of the motors even though the compressor shaft is 18 mm and the gear being driven at the end has a 12 mm bore making the shaft relatively stout so technically unlike the belt drive system, the shafts will all have a more centralized, torsional load instead of a heavy lateral load. I'm also planning to box-slot (slot that doesn't start at the end of the shaft) the shaft for the gear set screw to ensure no slippage and or shaft galling.

The compressor shaft gear is also heavy duty in stainless and is wider in both shank and teeth width compared to the motor gear and it appears I'll need to chuck it up and take about .100 off the overall width to clear the motor mount block internally. The motor gears are not in their final position in that picture, that's just a mockup to make sure the motors could be bolted down following drilling the block.