Brushless 1/8 Buggy

[RC-Monster Mike]

The Lehner xl1600 with 15/46 gearing on 14 cells in series will put you in the low 30 mph speed range and will run for a long time. i recommend running your batteries in series vs. in parallel, as you will get more benefit from the improved efficiency of the higher voltage. The xl2000 on the same cell count (also in series) with 12/46 gearing would be around the same speed, but would have more throttle control (higher rpms) and would also accomplish your goal. Either of these setups would be the better way to accomplish this vs. a faster motor (that will run hotter and draw more amps to accomplish the same thing) and parallel packs.

[Batfish]

All of my battery packs are 6-cell at this point. Could I expect 30ish from 12 cells with the xl1600?
My gearing will be either 15/47 or 16/47, as the spur is 47 and the two pinions I have ordered are 15 and 16, so it's close to what you mention.

[Batfish]

I PM'ed you as well, but I just noticed that the Lehner's have 1/8" shafts and I already ordered my 5mm pinions. Should I just stick with the Feigao for now?

[RC-Monster Mike]

15/47 on 12 cells with the xl1600 will put you at around 29mph. The 1/8" shaft and 5mm pinions is a snafu, though! I have 1/8" bore mod1 pinions, but they won't hold up to the hardened spur gear. I may have found a source for the hardened mod1 gears, but I need to do some research tomorrow to see if I can get them in with a 3.17mm bore (1/8"). If you go with the 15/47 gearing and a parallel set-up as you had mentioned, I would go with the 8L motor.

[Batfish]

So it looks like I'll start off with the 8L.
Keep in touch regarding the 1/8" mod1 gears and I'll probably get the Lehner as well, funds permitting.
I'll get the order going - thanks a ton for your help and attention!

:)

[RC-Monster Mike]

My pleasure. I am curious and look forward to your results with this setup. Please keep me posted!

[Batfish]

Just a little update:

The speed control and motor are at the post office - I'll be picking those up today.
I have started assembling the buggy kit. A word of advice on the OFNA Hyper 7 TQ Sport kit; if you're familiar with assembling kits you're probably better off not picking up the instructions. The instructions are pretty horrible overall. I think OFNA needs to re-write instructions for a kit assembly...these instructions read like most RTR manuals that just tell you what part goes where in case you ever need to replace something. It's going together pretty easy, however, and I plan on having it built in the next couple days.
If I'm lucky I'll get to take it on it's first run this weekend. :)

I'll be taking photos of my progress and will also do a full write up of my project and experiences with it.

[RC-Monster Mike]

Cool. I am looking forward to the buildup pictures and results.

[Batfish]

I got it running last night, albeit only for a couple minutes.

Here's the setup, then I have a question or two:

OFNA Hyper 7 TQ Sport kit
Feigao 8L motor (currently using a 15-tooth mod1 pinion and 47-tooth spur (I also have a 16-tooth pinion))
BK Warrior 9918 speed control (4mm gold connectors to the motor, Deans connector to the battery - soon to be replaced with PowerPoles)
Blue Bird 620MG steering servo (Torque: 126 oz.in, Speed: 0.15 sec./60° at 4.8V)
Hitec HFS-03MM 3-channel FM receiver
Airtronics M8 radio

I tested and ran it on one 6-cell unmatched GP3300 stick pack.

Lastly, my normal digital house scale (which measures only by half-pound increments) says the RTR setup with 6 cells weighs about 8 pounds. I'm pretty pleased with that, even though I know the scale may be off by a pound or so.

I didn't give it much more than 3/4 throttle because I didn't have everything secured yet. Even still, it was pretty quick and I'd say that even at 3/4 throttle it looks about as quick as my stock E-Maxx on 12 GP3300 cells in first gear. Unfortunately, I hit a little bump in my back yard and my servo wire got sucked through the pinion gear. It still works, but looks like an accordion now :) I'll probably end up splicing it if it shows any signs of trouble.

My question: I noticed a fair bit of cogging through the first 1/4 of the throttle, but it took off nice and smooth once I got through that "cogging range". Will the UBEC (Mike, do you have any yet?) help solve this, or is it something I should expect to live with? I did not try a receiver pack, but I'm pretty sure I do have the 4 dry cell box I got with a previous radio that I can try.

Second question: How many cells and/or how much voltage should I be able to safely put through this system? From the stats I've seen, I expect 14/15 cells or 18ish volts to be the top - correct me if I'm wrong. I'm just looking ahead for the inevitable urge to do speed runs :)

I expect to secure the components tonight and get a little movie recorded to demonstrate the "cogging range" I mentioned. I'll post a link tonight if I'm able to get it done.

[RC-Monster Mike]

If you only ran one 6 cell pack, the cogging is inevitable with the warrior. It will be minimized when you attach the other pack in parallel or add a receiver pack. On one pack, the voltage drop of the batteries causes problems for th controllers BEC. The 8L is good for 12 or 13 cells for everyday running, and could be pushed further (more cells) for the occasional high speed jaunt. I don't think the UBEC will help in this case (if the battery drops below 5.5 volts, the UBEC will go into bypass mode, resulting in the same issue), but I do have them back in stock. adding the second pack in parallel or a receiver pack will make a big difference, though.
I am definately looking forward to the video!

[Batfish]

The video for Phase 1 is up at rcpics.net.
http://www.rcpics.net/view_single.php?medid=54649

edit - forgot to mention that it's 11+MB, just so you know

I put in some titles so you know what you're looking at.

Let me know if you have any questions.

If it looks like everything is held in with zip ties, it's because everything IS held in with zip ties :)

Provided my connectors actually show up via UPS tomorrow, as they are supposed to, I'll have two 6-cell packs wired parallel to test out tomorrow night.
Also, provided it's running well enough and I have the body ready, I'll be trying it out at my local indoor track (www.rcexcitement.com) on Wednesday night. I may be able to get video of it at the track and will post it if I do.

It's great so far and I still have my photos and write-up to do for the current progress.

[Batfish]

Also...
Mike, you mentioned that cogging is inevitable with the Warrior at 6 cells...what about 7 cells? 8? I have the equipment to do all 3, and expect to do all 3.
What about the MGM 120 - cogging on 6 cells with that one? 7? 8?

Thank you.

[RC-Monster Mike]

The warrior really only has the problem when the voltage drops below 5.5 volts, so if you run the packs in parallel, the problem will go away. The MGM controllers (and soon, the new BK controllers) have a lower BEC cutoff voltage, so the problem isn't there. On 8 cells, the problem pretty much disappears on the warrior, unless the batteries are real bad.

[Serum]

If you have got a problem with the weight/size of the 8-10 pack, you could also use the new GP2200 cells!

[Batfish]

I don't have a problem with weight/size yet, but I haven't found a permanent mounting for the cells yet, either.

I was able to bring it to my local shop and "wow" a couple of people, including one who runs monster trucks all the time and has been thinking about going brushless in his TXT (Mike, I may be sending him your way if he's serious).

I continue to use my crappy 3000 cells while I work on a permanent mounting for good cells. I don't want to rip apart any GP3300 packs because some velcro let go, heh. :)

The 1/8th scale is a little too big for the new track layout at my shop, but it was a little it of fun running it there anyway and having people ask "They let you run nitro indoors?". Guess they didn't bother to listen to it first, heh.

The only problems I had were mechanical with the buggy: a battery pack popped out and ripped a connector off, and a couple screws loosened up (just needed to be re-tightened). The crappy cells got hotter and stayed hotter than either the motor or controller. Speaking of which, should my motor be hotter than the controller with this setup? Neither is actually "hot", but the motor definitely has the higher temp. I didn't measure it since I know it was nowhere near any danger zone - I'm just curious.

On a couple runs in the parking lot, I was able to get to top speed with the 6-cell x 2 parallel configuration. I'd say the top speed there was about 20ish with the crappy cells. I then switched, on the same cells, to 12 series and figure I was closer to 30, but I don't think there was enough room to get to top speed. I expect both speeds to increase dramatically with good cells.

Mike - I still notice very weak braking power, as I had mentioned in my email, even after re-programming. Any thoughts as to what I should check for? I've read posts from people, here and elsewhere, that have very similar setups in E-Maxxes that have to be careful to avoid doing endos, but my buggy stops only about half as fast as letting it coast to a stop on it's own. It took a good 20 feet or more to stop from about 25MPH. I expected it to be better.
EDIT - Mike, I also wanted to mention that running the receiver pack with 4 fresh alkalines AND having the BEC enabled on the 9918 definitely reduced the cogging on 6 crappy cells...definitely.

No video tonight, but I had fun :)

Next steps:
1 - find a stable mounting system for the batteries
2 - I have a small digital thermometer with a sensor lead that I plan on mounting on the speed control and putting the display where I can see it from the outside of the body. I also have a small CPU fan that I'll add to the 3rd channel of the receiver and mount somewhere.
3 - I also want to add an ON/OFF switch to the setup. Any suggestions on what to use that can handle the load and not hurt the system? My personal preference has been to install batteries, put the body on, turn the R/C on, and go. I never liked a system that's on as soon as the battery is connected.