Lightweight 1/8 buggy project
 

Hi there

I am finally converting a 1/8 nitro buggy to electric with the following goals:

• Lighter than nitro original
• At least 15 min runtime going the same speed as nitros on (European style) race track

Are there examples of such buggies? All electric 1/8 buggies I've seen are heavier than the nitro version (maybe except the conversions of Mr. Constructor, which don't use a nitro chassis).

Attached are pictures of my self-designed aluminium motor mount and self-made carbon prepreg battery holder.

Regards
Thomas

Even though some of the electric buggies are a bit heavier than their nitro counter parts, what makes the electric conversions so popular is the sheer acceleration and torque of the brushless set ups. My electric truggy is heavier than my friends nitro truggy although he tries, he cannot keep up with mine. So if they are a bit heavier it can be more than made up. However, the lighter you can keep it the better for sure.

Nice job on both pieces.

You could use the Losi 810, and use a light 3s setup...

TG

something like this?

http://www.rc-monster.com/forum/show...on+fiber+8ight

Thanks for the links. There are some pretty light BL buggies out there. My goal was choosing lightweight powertrain components, not just saving weight by using carbon etc.

I have achieved the first goal, my electric conversion is 130 g lighter than my nitro version of the same buggy (even with empty tank). I chose a very small motor to avoid overpowering the buggy (it's for racing, not highspeed bashing), but it didn't go as planned: These Neu motors just make unbelievable power, the buggy is crazy fast.

I haven't been to the track to experience driveability and runtime. What I noticed is that without mechanical brakes, it might be harder to throw the rear end around a corner off-power. But I guess I can adjust caster, ackermann and the dampers to tune that.

I thought this thread needs some more pictures. Here she is just before the shakedown today:

Can you tell us which buggy that is, and the turn/kv for the motor? How many cells are you running it on? Thanks

Thomas G

Hi Thomas

Yes of course, here you go.

Buggy: Very old TTR S3 EB4 with an aftermarket flat chassis plate
Motor: Tekno Neu 1509/2y/f (1820 kV)
ESC: Mamba Max Pro
Batteries: 2x 3s1p (-> 6s1p) Kokam 2400 mAh 30C

I will probably switch this powertrain over to a new buggy next year (if it works well). Will have to see which one fits the layout, or make my own chassis plate.

Can you please tell me more about the carbon battery trays? You made them yourself? What was the process?

Hi

Yes, I made them myself, at the university where I study. I used carbon prepreg, in this case twill with roughly 200 gsm. For the battery trays, I used a positive mould (plug) made of wood, which I simply cut to the size of the batteries plus some additional space. I used release film and laid three layers of prepreg onto the mould. Then I put them in a vacuum bag and into the autoclave at 2 bar pressure and 130°C to cure for two hours.

One battery tray (without velcro strap and double-sided tape) weighs 25 g. The carbon stripes for mounting with screws are glued on.

I will try to go to the race track tomorrow, to find out the runtime, but the weather is a bit unsure.

6a on 1800 kv is ludacris speed for sure! Mine was insane on 1700 kv and still plenty fast on 1400 kv now. My rc8 is 3330g and has all the lightweight driveline parts too. A lighter buggy runs longer and cooler but I had to change my setup to make it drivable. I like how nimble it is now but I have noticed it gets tossed around a little more in the rough stuff. IMO reducing rotating mass is where it's at. Don't worry about overall weight as much, reduce load on the motor to keep the power system happy and it will reward you with insane amounts of power as you have found(neu motors are my favorite for this reason).

I'm wondering if efficiency is going up with 0° timing or if there is an optimal spot for my motor. Torque and speed are plenty, so I'm not looking for best power, but highest efficiency.
As said, I'm using a Mamba Max Pro with Tekno Neu 1509/2y. I'm trying to find the best settings for good drivability and long runtime ond an offroad track.

0 degrees is the most efficient. When you go up you gain rpm and loose efficiency. I always run 0 on my 1/8

¿weight rtr of this car? :lol:

It weighs 3430 g ready to run, compared to my nitro S3 which is 3560 g with empty tank. 51% of the weight is on the rear tires, left/right is <1% off balance (at least my measurements said so).

I was running two battery packs on a dirt track and one in a skate park. On the track, top speed seemed just right, runtime was roughly 12 min with 5° timing. With 25% punch control, the buggy was well controllable. I will probably get a pair of bigger batteries to increase runtime, but they have to fit my trays.

Thats pretty good. I have found that the lighter buggies are a handfull to drive though and take a bit of setup work to tame. My rc8 is 3330g rtr and rips but took a bit of unconventional tuning to get it to work. Your setup is lookin good too keep up the good work.

¿photos :lol:?

yeah photos are nice huh? sorry guys had to get to a pc, iphone wont do it. 1400kv on 2650 6s 40c 3330-3400 rtr depending on the tires. use about 600-700 mah on a medium size indoor clay track. got some 6s 3600 30c's for long outdoor mains with the noisemakers:rofl:. enjoy!

ps. towers and arms are the new worlds stuff. had it for a few months and really like the responsiveness it added to the car.

Looks nice. Wow, that front shock tower is beefy, about 4 mm? What kind of setup changes did you make? If that is a CFRP chassis, you might have raised the CF quite a bit, which increases roll.
You used only 700 mAh for a 5 min qualifier? Or 700 mAh per minute?

I realized the biggest LiPos that fit my trays hold about 2600 mAh. Yesterday, I got two Fullymax 3S 2600 mAh 35C really cheap (48 USD per pack, half as much as my Kokam 2400). I haven't mounted them, but looking forward to not having to wait 30 min between runs.

Front tower is 5mm and it uses roughly 700mah in a five minute race on a medium size indoor track with a 1400kv on 6s. Geared for about 38-40 mph. Roll center has changed slightly but more than anything the worlds geometry was the biggest change. Had to stiffen the shocks a bit and some other fine tuning for my driving style but mostly learn how to drive the new car with all the turn in. It's a tad looser than my rear battery b setup but I will probably move the pack to the rear and see how it does. As it is now it has tons of steering but not as stable or as much corner speed as with the pack in the rear.

http://www.cochesrc.com/foros/1-8-tt...-de-1-8tt.html



ojoloco ............. Xray 808 2009 ..................... 3283
maxkarmona......nexx8............................. .......3345
dobro.................Bergonzoni R-1.....................3370
robertiro ............xray 808e.............................3400
ojoloco...............DNX408...................... ..........3400
mariano..............MBX6 ...................................3450
frasil...................losi 2.0E...............................3580
carrcrc................RC8e....................... ..............3600
altea..................mp777 sp2............................3600
mateu ................mbx6e............................. .....3650
rancapiedras......mbx5r........................... .........3600
tonizz.................eb4 s2...................................3500
fabulosoales......Hyper 9-GL............................3700
fraque................MP9e ....................................3700
buhos.................LRP s8 bxe............................3700
caesar77............RC8Be......................... ...........3700
robertiro.............rc8......................... ................3750
mac47................Nexx8........................ .............3720
unrealer .............RC8Be................................ ....3700
j30......................8ight.................... ...................3700
fastereto ............mp777e................................ . 3700
Alberto Menor.....rc8be................................... ...3750
shaq145.............hyper 9.5 ...............................3800
titusx................. Losi 8ight 2.0 E.......................3800
santirustler.........Losi 2.0...................................3800
elpresi.................rc8be..... ................................3800
jcacia..................kyosho e ................................3800
fran 1978...........rc8................................ ...........3900
x-y......................hyper 8 ...................................3900
toni aloy..............mugen 5 e...............................4000
x-y.......................mbx5re ..................................4100

I had a race last weekend and was using my new Fullymax 3s 2600 mAh 35C (two in series) along my Kokam 3s 2500 mAh 30C. I'm able to get 15 min of runtime, but it depends on driving style. Top speed is slightly faster than the nitros. So far, I'm very happy with my Fullymax LiPos, even though they cost half as much as the Kokams.

The torque of this powertrain is unbelievable. We have a big jump (with very high friction surface) which the nitros need quite some throttle to clear. I would just roll up to the jump slowly, give some throttle and land 2 m after the landing ramp. I need to play with my Castle Link a lot more, though. Went to 0° timing and 50% punch control already.

Temps after a 20 min final (25°C air temp):
Motor: 75°C
ESC: 52°C
Batteries: 40°C

However, my buggy handles like crap (it's six years old!) and I need to mount the battery containers better. I'll probably get a used Xray 808 at the end of the season, or two (one nitro, one electric). But I'm very happy with the powertrain so far. Only change I am thinking about is somehow making room for "standard" length batteries.

Can you talk about what you did on this? CF tower, chassis, what else?