Overkilling the Go-Kart Again (67.2v Chevy Volt battery -> 87.6v Headway 38120HP)

[EpsilonZero]

Or how about this one? It is over five minutes long.

 

[Willie1]

Gotta say I like the feel of acceleration over the giggle factor of tire spin.
And I realize that sticky rear tires require soft front tires to maintain steering,
which causes a debris issue. Maybe fitting (removable) front fenders when the
soft front tires are on might be a solution.

 

[EpsilonZero]

Gotta say I like the feel of acceleration over the giggle factor of tire spin.
And I realize that sticky rear tires require soft front tires to maintain steering,
which causes a debris issue. Maybe fitting (removable) front fenders when the
soft front tires are on might be a solution.

I made three types of front fenders and have come to the conclusion that, unless I basically full enclose the tires, debris ends up hitting me in the face more often rather than less with the fenders on. It seems ridiculous; pebbles will hit the fender and slow down, but bounce in front of the kart and then into the kart while airborne. With no fenders at least they mostly follow a trajectory in line with the wheel. I had the best luck with flaps, but I made them for narrower tires and modified the hardware for the fenders... so now the tires just go naked!

 

[EpsilonZero]

 

[Bmr4Karts]

What's your gearing?

 

[EpsilonZero]

What's your gearing?

14:44

 

[Bmr4Karts]

14:44

If I'm doing my math right with your 11 inch tires that's good for 60 mph. So did you set an RPM limit or do run it to 60 mph?

 

[EpsilonZero]

If I'm doing my math right with your 11 inch tires that's good for 60 mph. So did you set an RPM limit or do run it to 60 mph?

The OD on the tires is 10.5. I set the limit at 6000 or 6500, but I haven't taken it to my preferred road for speed testing yet to see if it will go any faster. It does spin up to 6000 rpm with the wheels in the air with a 6000 rpm limit (from initial tests). If it can spin at least 6000rpm under load, that would be 60mph, but I'm not holding my breath. I'll take it out for more testing as soon as I get a chance.

 

[Bmr4Karts]

The OD on the tires is 10.5. I set the limit at 6000 or 6500, but I haven't taken it to my preferred road for speed testing yet to see if it will go any faster. It does spin up to 6000 rpm with the wheels in the air with a 6000 rpm limit (from initial tests). If it can spin at least 6000rpm under load, that would be 60mph, but I'm not holding my breath. I'll take it out for more testing as soon as I get a chance.

My original Manco kart ran a 20/53 and had decent acceleration with only a 64v pack. I bet both of our karts could hit 70 mph+ with that gearing ratio.

 

[EpsilonZero]

My original Manco kart ran a 20/53 and had decent acceleration with only a 64v pack. I bet both of our karts could hit 70 mph+ with that gearing ratio.

I was able to hit 68+with my ME1717, but it was at the limits of what its power could deliver and acceleration was bad. I have no doubt the latest configuration could easily pass 70 with a gearing change.

 

[EpsilonZero]

I finally managed to slightly bend my Flexpruf steel axle. It may have been due to catching air on a large bump around a manhole cover in the road. I also noticed more wear on the inboard of my rear tires than the outboard during the last tire change and decided to add a third bearing in the center to permanently alleviate these issues.

I welded a piece of flat bar to a hanger and welded it to both sides of my engine mount plate. I took it out for a test ride and everything seems good to go. Hopefully it keeps the new axle straight and improves the tire wear. Also, bonus 0-60 footage:

I swapped from 14/36 (2.57) to 13/40 (3.08) after the video since I don't ever go 60+MPH and acceleration was really dropping off after 50mph anyways due to wind resistance and no field weakening on this controller. I got a 13t since my 12t wouldn't stop skipping under load and swapped the axle sprocket accordingly. The swap hacks 10mph off my top speed to a more reasonable 50+MPH.

 

[Molloy]

One thing to think about wrt bearings and having more than 2 axially along a shaft. Unless they are perfectly aligned, there will always be a slight bind on one of the bearings, which could cause premature wear on the bearing races/rollers. When you have two, even with a misalignment, it's usually within the tolerance of the bearing.

 

[EpsilonZero]

One thing to think about wrt bearings and having more than 2 axially along a shaft. Unless they are perfectly aligned, there will always be a slight bind on one of the bearings, which could cause premature wear on the bearing races/rollers. When you have two, even with a misalignment, it's usually within the tolerance of the bearing.

I tacked the hanger in without clamping and verified the axle slid freely through the bearings before fully welding.

 

[EpsilonZero]

A new test run with different gearing. I discovered Kelly finally added field weakening to this series of controllers, so I ordered one and the next video should feature a test run with it.

 

[Molloy]

A new test run with different gearing. I discovered Kelly finally added field weakening to this series of controllers, so I ordered one and the next video should feature a test run with it.

Looks like it launches hard

 

[EpsilonZero]

Here's the test run with the new KLS96701-8080NPS w/field weakening:

 

[Functional Artist]

Lookin' good!

Could ya give us some commentary
...& tell us what is going on here

Like what is different than, your previous set up
...& why

 

[EpsilonZero]

Lookin' good!

Could ya give us some commentary
...& tell us what is going on here

Like what is different than, your previous set up
...& why

I swapped out the controller for one with field weakening (FW) and ran it with maximum FW and a cutoff at 5500rpm. FW will allow greater torque output after peak torque than normal at the expense of additional current (and heat). It can also allow the motor to spin to a higher max RPM.

I had problems with FW previously on my KLS7250-NR (special order FW... not advertised) where attempting coast in the overspeed region (faster than the raw voltage normally can spin the motor) would result in extreme unwanted regenerative braking, which was quite scary and dangerous. I tried it with two motors and two batteries with the same bad results. So, I couldn't really use that FW implementation without major trade-offs.

These controllers will often overshoot my set limit a bit (especially with my torque-centric settings) and that happened here, running up to 59mph (~5900rpm). Without FW, the motor will spin up to about 5500rpm. That put the kart ~400rpm into over-speed. This time, though, the power just cut and the kart coasted rather than braking violently until back below 5500rpm (this is good). Basically, I think it may be that Kelly changed their implementation of field weakening so that the excitation current continues to be employed when coasting in the overspeed region rather than just allowing field weakening collapse and turning the system into a sudden 100% generator. I could raise the limit and do more testing beyond 60mph (I've done 68 on the KLS7250-NR... scary), but this is pretty much where I wanted to be with performance.

These are the different major components I have used over the last few years.

Motors:
ME1305->ME1717->ME1719->ME1904 (sin/cos)
Controllers:
KLS-6030H->KLS7250-NR (FW)->KLS72701-8080NPS (sin/cos)->KLS96701-8080NPS (sin/cos, FW)
Batteries:
RELiON Insight 48v LiFePO4->Chevy Volt 16s->Headway 38120HP 24s4p

My buddy with a built 212 wants to drag race with his new carburetor and other upgrades, so be looking for that video to appear in the near future.

 

[EpsilonZero]

...and here's the video.

 

[Functional Artist]

Zac:

I wasn't ready

When you see me go
...then, you go

Maybe give me a roll
...like, a few seconds head start

That was a bad run

I'm so em-barr-assed (I just threw that one in)