Help with hyper 7, 9xl gearing
 

I have a hyper 7 buggy with a 44 and 46 tooth plastic spurs. The motor I will be using is a wanderer 9xl. The esc is a bk7020. The batteries I will be using are 6s1p a123 cells. I am hoping to find gearing that will not drop the voltage too much on this 1p setup and still give decent performance. Am I asking too much from just six of these cells? I will eventually buy six more cells and run 2p, however this is what I have for now. I need suggestions on what pinion(s) to start with. Thanks,

Lydiasdad

Well, I'd go with the larger 46T spur definitely. Then, you'll probably want a low pinion, like 12T. Top speed won't be super and you'll probably still get some voltage drop on take-off.

I received my buggy on Thursday and I finished the conversion Sunday night. I was surprised how easy it was to convert. This is my first 1/8 and I am very impressed, very beefy.
I made a carbon fiber center diff mount and motor mount. I moved the chassis braces from the chassis to the new center diff mount. This gave me more room on the chassis and strengthened the diff mount. I went with 12/44 gearing and am very happy with the performance. I have not run the batteries down so I don't know about runtime yet.
I still have to make a support for the rear of the motor. It's pretty stiff but I want to make sure. I also plan on getting the motor clamp/heat sink. On to the pics.

Nice! Wow, you sure have quite a motor adjustment there! That's probably the biggest adjustment slot I've ever seen! You should have plenty of options for gearing.

I too would find a way to support the rear of the motor. Landing those jumps puts a lot of strain on the front mount. Maybe wedge a piece of rubber under there?

Your buggy looks great. Mike is actually making me a motor mount right now for my 1/8 buggy conversion. What kind of speeds do you think you are getting?

Have fun with it.

I'm not sure about the top speed, 35mph? I going to do some speed tests this weekend so I will post the results. I do know the acceleration is crazy. Its at top speed in 1 to 1.5 seconds, literally. I really underestimated these cells. I just wish they were bigger capacity. Yeah, a little over board on the motor adjustment:005:

First off, thanks for the great pics of how the cells are mounted in the buggy. That may be enough to make be want to go to A123 cells!

Good guess on the speed. I'd say you are in the 35 - 37 mph range. 13T will get you into 40 mph. Even with that gearing, you are only running 29% overdrive. I say "only" because I run my 10L at 33% overdrive with no problems. I'd say you could even push that to a 14T pinion if you wanted, with that XL can you have.

Sleeb

Your welcome for the pics.:027: I could not be happier with these cells. I highly recommend them. I was concerned about the voltage drop running a 1p setup, but it doesn't seem to be an issue. Temps are good on everything so far. I have only ran it for 5 minutes at a time, but with hard acceleration and braking the motor is only warm to the touch and the batts were room temp. I am worried about run time but I think I will just buy a couple more 3s packs so I can just switch them out.

I'm glad the voltage doesn't drop much. Truthfully, I figured you'd have a decent amount of voltage droop, but it sounds like it's working fine for you.

Voltage shouldn't droop too much as those cells in a 1P configuration are supposed to be able to do 70A without a problem. The 9XL is a 74A "max" motor, so if it spikes above 74A, it's very brief.

So, if ya use higher turn, lower amp draw motors and then you can get away with 1P setups with the A123 cells.

Sleeb

Plus my buggy is under 8 pounds. That helps with the amp draw too. I am running the center diff locked for now also.
I just can't believe the torque it has. When I finished it Sunday night, I programed the speed control and set it down on the living room carpet for a test "run". I pegged the throttle and it did a violent wheelie, flipping back words, knocking every screw out of my parts box!:007: I will try to get a vid up.

I wanted to post finished pics and report on the performance of this setup. As it sits now it is 8lbs 3oz. I charged by batteries and ran it very hard on concrete. I got 12-13 mins of runtime. Batteries were warm but motor was hot so I put some sinks on the motor. I also put a piece of foam rubber under the motor to support the rear.

Nice! Sounds like you have decent runtime out of 6s1p! That's good to hear. Have you jumped it yet? If so, how's the balance? I like the color scheme too - looks like you matched the rims and paint nicely.

BTW, I'm sure you know this, but you can shave a few more ounces by using a UBEC instead of the receiver pack. :dft012:

I think I will get a ubec but I'm worried abut glitching. That seems pretty common. I have not jumped it yet but it feels very balanced. Thanks on the paint, it's what the hobby store had.:005:

I'm using a Spektrum so that may have something to do with it, but I don't have any glitching. I do use a 1,000uF capacitor in the unused CH3 receiver port to help filter out any noise on the DC line. And I also try to keep the UBEC away from the receiver, or at least shield it somewhat by having some metal between it and the receiver. So far, one or all of those things have worked well.