HandyRacing

Project updates will be posted on the thread as comments so we can try to keep this a "linear timeline" BBS conversation.....

We thought about a 1/10 scale Jammin XRT.5 stadium truck chassis, but as we intend to race and there isn't a class for that we went all out with a 1/8 scale buggy. (Editors note, I feel this 1/8 scale buggy brushless conversion racing head to head against Nitros to be the most excting thing going in RC racing, and predict this summer will see LOTS of RC media attention).

See the 1/8 scale buggy and truggy results here for our local peer group, which have been mucho helpful as we asked a thousand questions during our project design, parts selection and test track phases. THANK YOU GUYS.

http://www.rcproductdesigns.com/washtenaw_track.htm


The project: Pick up a mint condition used Jammin X1CR, sans unneeded Nitro engine for a small fraction of retail. Then select and pick up some odds and ends spare parts for motor mount and battery tray. Start working on a plan for battery, speed control, motor, other control devices, cooling engineering, and "additional" ancillary equipment.

Choices to be made RE motive power: Since we already have a pair of 7.4 volt 4000 mah MaxAmp LiPos, we plan to run them in series for 14.8 volts and 4000 ma. The ideal motor seems to be the NEU but they also seem to be hard to come by, so we're starting out with a Feigao 540 7XL. Most folks we know are running the Castle Mamba Max (MM), but since we already have a Traxxas VXL it might be fun to use it if it will work, the primary concern being the "Over voltage" feature crapping us to "failsafe" mode. With the 3 cell LiPo rating of the VXL giving us 11.1 volts and the spec rating of 200 amps the VXL should have wattage handling capability of 2220 watts. If we can run @ 14.4 volts, the Feigao runs at 95 amps max, which would only tax the VXL to 1368 watts which it might seem we have some power handling breathing room.

With the rumored Castle Mamba Monster Max (MMM) on the horizon it would seem pointless to spend the money now for a current MM if the VXL will do the job.

The folks on the track seem to run with the MM ESC now with some success but they also do have to manage heat carefully with little room to spare. They also prefer to run the NEU motor rumored to run more efficiently than the Feigao (4 poles vs 2 poles).

Some cooling engineering with heat sinks and fans of course needing to be part of the master plan.

Numerous trade Mags have done "reviews" of prototype set ups, one even including wood parts!

Numerous vendors are selling various conversion parts at various price points, some ESC / motor vendors are selling "systems" although this market seems to be underdeveloped and in its infancy.

I'm most impressed with the engineering and proving ground efforts of www.RCProductDesigns.com although many others have also worked on developing this new frontier.

Anyone care to discuss the various pros and cons of the various motor options in this higher power range?

Experience at pushing the Traxxas VXL to higher performance ranges? Other ESC options?

Experience with running multiple fans and devices with a BEC?

Gearing experience with various size and surface characteristic tracks?

Experience with various LiPo sizes working for the duration of various time length mains?

Experience with optimal steering servos for the heavier vehicle?

Other racing issues such as ROAR sanctioned or exhibition events?

Links:

www.RCProductDesigns.com *

See RC Driver January 2008 edition, "Projects" (not available on line). http://www.rcdriver.com

http://www.rcuniverse.com/forum/m_69...tm.htm#6987110

http://www.rcuniverse.com/magazine/a...article_id=953

*Not affiliated with RC Product Designs (other than occasional customer)


Pictures / performance testing as the project develops.......


(Spell check and minor sentence structure edits as follow up)

helishack

This is an intriguing topic and I decided to pick up a used XTM X-Terminator to try this out on. So... for $80 for the buggy I picked one up and picked up about $25 in parts to get it running smoothly. Lot's of fun (I've never owned a 1/8 buggy before). It's SOLID and carries some decent weight. Man this thing screams and works REALLY well. I have a 1/10th scale from many moons ago (Losi XXX-NT) and that's a lot of fun too.

Anyway, the pics below describe what I did to convert my 1/8 nitro buggy to brushless. I ordered an 11T hardened pinion (MOD1) from RC-Monster. I'll order larger sizes as I learn more. The aluminum for the motor mount was from the "hobby" pile at the local metal supply company (0.25 per piece - what a deal!).

[hr]
(update)
Here's the chassis after removing the nitro-engine related components:




Here are the "nitro parts" that got removed... time to put these on Craigslist San Diego Btw, in the background you can just see the electric scooter that I've "upgraded" to 36v @ 20AH & 750W. I'm adding a beastly relay to it this evening. My daughter and I burn rubber on that thing! [:-]


Servo tray cut apart to remove the excess metal since I'm not going to use the standard braking system (we'll see if this is a good idea or not since braking via the motor will definitely add to the work/heat it will have to deal with. Also shown are all of the parts of the brake assembly.



Now that I've gotten that all out of the way, I remounted the center diff.


[hr]
Okay, now we get to the really fun parts!

Let's start with the 38mm x 42mm piece of pre-cut aluminum that I picked up at the local metal supply company...



Threading aluminum is "interesting". With the previous motor mount I broke the same tap ~twice~ until I learned to have patience and tap this differently than ferrous/harder metals.


Even though you can't tell from the pic, the threads are excellent!


I'm using an existing motor that I had from a T-Rex 600 (1620kVm). I know, not many kVm, but it didn't cost me a penny, so I'll test with this for starters. It will definitely be slow... even at 22v


New mounting holes. I'll countersink later - remember, this is a proof-of-concept for myself...



Everything fits well and gear mesh (backlash) is exactly as measured!





Esc mount sizing and finished product



rx mount layout and finished look




So, here it is... I'll be running 4 batts for 4200mAh and 22.2v



Next and final step, pick up an ESC that can handle 22.2v (for my 6S2P) 100A continuous and peak over 12A.

Any observations, comments and suggestions are appreciated. By the way, this project cost me 1 hour and about $18 (for the pinion and the 4 aluminum "hobby" pieces.

I'll follow up after I get the ESC and install it. From there I'll work on the gearing and final motor selection.

Jeff

HandyRacing

Thanks for the great details. We picked up a motor mount from eBay, and a used battery tray from the local track.

Starting from scratch, we had to buy a motor (Feigao for around $80), the NEU being the motor of choice but it runs for around $240 list price and seems to be in short supply as they (NEU) are ramping up with this segment of the market?????? (NEU seems to be big in the RC airplane world).

Various other parts on the way, steering servo, BEC etc etc.....

Then there's the new tires and rims, body, we didnt have an 1/8th scale to begin with, this project would be a lot easier for existing Nitro owners as many of the basics would be in place.

The Mod1 pinions seem to be the suggested gears of choice, and although they are said to work with the stock metal spurs, the Kyosho 46 plastic spur seems to be the most recommended for best pinion wear. The hardened pinions at $12 or $13 each plus mailing vs $5 for the plastic spur which is also said to hold up very well. Running with the plastic spur, there is also some doubt the extra expense of the hardened pinions are required, and regular steel pinions will work OK.

Of course, once we actually get to powered testing, performance on the track under race conditions will be the proof in the pudding.

The guys at the www.RCProductDesigns.com Forum have LOTS of experience and have helped us out a great deal on shortening the learning curve. In the "Washtenaw Track" section are results from the 1/8th scale rigs under race conditions on a small indoor track and running 5 minute races. The outdoor race conditions being another story with bigger tracks and longer races making heat management, batteries, and gearing all more intense and needing careful attention.

We hope to run for the first time next weekend, will update with more details and lessons learned as we get to actually rolling on the track condition.

I'm REALLY curious how hard we can push the Traxxas VXL ESC and how it will perform compared to the MM.

helishack

You're welcome - and I appreciate you actually starting this tread. The timing was perfect. I'm Googling around to find the best balance with price/performance. I wish I didn't sell my 120A ESC and 6v uBEC a couple of months ago. They would have been perfect to test with - even though the ESC wasn't actually designed for a car/truck

Btw, I updated my initial post to show the original parts that were removed.

Yeah, those little pinions do cost a bit - then to add shipping on top of that... It's still worth it when I think that I won't be replacing clutch shoes/bell on this buggy any more. Come to think of it, I have A LOT of nitro spares and parts that need to get put up for sale.

My thoughts, exactly. Once we start running with various configurations we'll have a much better idea on tweaks and fixes. I already know that I'll be "under-geared" but if I throw some paddle tires on the buggy it should have a blast with a Widowmaker-type hill-climb!

I'm used to flying 600-class electric helis and with all that torque for the 600mm rotors and some hard 3D, I've seen some amazing failures with plastic, aluminum and steel. Obviously this is not the same, and nothing is going to "fall from the sky" but I am wary of the extreme torque of electric motors. My (electric) uber-scooters will chew themselves apart if I miscalculate current, strength, tolerances, etc.

I wasn't aware of RCProductDesigns. Thanks, I'll check them out. I was going to simply order a motor mount, but for $40-$60 (versus .25 cents) I decided I'd drill and tap one out myself. Actually, I did break a $3.50 tap and had to use a second piece of aluminum so the total motor mount cost went up to $4.00. Darn it! Actually, I will have to re-machine the bolt holes for the motor when I add a larger pinion. I need to allow for the motor to be moved away from the center diff as I try different pinion sizes.

Let's keep this poject going and everyone informed. It's a lot of fun and I'm sure it will be plenty worth it in the end.

Jeff

HandyRacing

I emailed Dan at RC Product Designs, hopefully he'll keep an eye out on this post and share some lessons learned from time to time.

For us do-it-yourselfers, buying the Traxxas E-Maxx motor mount for about $6 gives a good cheap pattern for copying the geometry for making new motor mounts (or just use half of it). It seems an inexpensive time and trouble saver for taking measurements and making prototype parts. We thought about a dual Velineon set up for awhile and were going to use the motor mount, but decided to keep it simple and stick with one motor (we think dual brushless on the same spur might be a feedback and motor control problem).

You're very welcome for the thread, we plan on racing competitively this coming summer and as we take pics and get some testing results I hope to keep this thread updated. Hopefully others will also add their projects like you did - we can all learn together.

HandyRacing

Here is a link to "patented" conversion kit history from 2005. Lots of discussion and pics (albeit one must be a member to see the pics).

http://forums.radiocontrolzone.com/s...d.php?t=196185

HandyRacing

Here is a link to further discussion RE the RC Product Designs conversion kits. LOTS of discussion RE braking differences between the traditional front / rear adjustability of the Nitro setup and the breaking via the motor of the Brushless setup.

http://rctech.net/forum/showthread.php?t=158327

(corrected for typos)

RichieD

helishack

I'm very interested in learning more - this project is a fun challenge.

RichieD, thanks for chiming in! Considering that some of us have day jobs that don't even closely resemble what we do for hobbies, it would be expected that you won't find CNC quality work from do-it-yourself folks all that often. I take no offense actually - I'm a hobbyist and enjoy hacking away at my cars. Now my helis are another story - they get professionally machined parts - for obvious reasons.

From what I've read, a lot of people are using 14.4v. It seems that with the right motor and gearing they get their desired results on 1/8 buggies. The system I'm building will handle up to 6S lipos for 22.2v - which will allow me to drop to 5S or 4S depending on the kVm, gearing, weight, track, etc. Lot's of variables here... The decision on 6S will be based on weight and whether or not I need all of that voltage (which drops the current draw - as long as the system can support 22.2v).

It would be great to see a how-to or some points on how to do things better. I'm all ears on this topic...

Thanks,

Jeff

HandyRacing

Well RD, as said by the owner of the "botch-job" I also appreciate your input. I would ask that we keep the "tone" a little more up beat and condusive to working together.

My impression is that Jeff, just like myself is experimenting with some prototype parts development and in the interest of the creative process, our parts may well be a little rough around the edges at first, but in the spirit of "why pay retail" when you can do-it-yourself - our end results may well be lighter, stronger, and cheaper.

As far as 14.8 volts (4 cell LiPo), it seems to be a basic price point threshold. The cost of the batteries, and ESC that operate in this range (Mamba Max) being sort of the entry point to being fast and reliable. If we want to upgrade to 5 cell or 6 cell (LiPo) batteries, we can also probably expect to pay $100 more for the ESC. The soon-I-hope Mamba Monster Max may open some new doors for power / performance / price point. I'm not entirely sure what higher voltages the NEU motors will handle as I don't like to quote numbers and techno facts from memory, but I can tell you that the Mamba Max coupled to an NEU and 4 (or 5 cell) LiPos absolutely fly around the track. You might also find in the various trade journals and discussion boards, many folks are operating at the 14.8 volt range (many in recent years also using sub-C cells) and quite pleased with speeds. Managing heat being the key to success. I have a few ideas in this area, not yet done with developement and testing or ready to share.

The head to head comparison of the LOSI 8ights was enlightening:

http://www.rcuniverse.com/magazine/a...article_id=953

An interesting point of note, they ran with 11.1 volts.

I'm not an electrical or electronics engineer (actually I do heat and cooling engineering), and we aren't talking laboratory bench testing with dynamometers here, not to mention speed runs on the Bonneville Salt Flats - what I want to see is head to head on the track for 30 minute mains in 100 degree summer heat. May the best man (or woman) win.

That all being said, I'm told the currently available HV package (from Novak?) doesn't perform, it was designed for an E-Maxx instead of a racing 1/8 scale buggy, and in all honesty - those of us do-it-yourselfers can be credited for inventing this new RC opportunity.

And besides, as an old fart I like the peace and quiet of the electrics over the Nitro. But like I said above, the proof will be in the pudding - NOT just on the track, but also in the elegance of our designs, and the robustness of our rigs.

Jeff was kind enough to share the early development stages of his project, I hope to also as soon as possible.

Please feel free to share pics and performance of your project(s) also. This is an open invitation to everyone to share their projects, that's why I started this post - so we can all learn.

HandyRacing

Following is a brief summary of the motor mount we decided to try for Phase I:

We picked it up on eBay for $25. It seems for material selection, measuring and machine time, it was worth the cost for a quick and inexpensive place to start. As noted above, our thoughts for a dual Velineon system and the Traxxas E-Maxx motor mount were discarded for a sinlge motor / ESC design.

First trouble we had was the lower bracket portion was above the chassis so we had to make a spacer to mate up properly. Second, the central diff drive hole was not positioned properly to match up to the diff mount screws. We were able to get around these with some "adjustments"

We also made our own "shelf / bracket" for electronics mounting, so we did not use the top plate that came with the package.

I like the idea of using angle stock, as I think the lower bracket anchored to the chassis will provide stiffness given the weight of the cantilevered motor would normally only be supported by either just bolts thru the bottom, or anchoring to the diff assembly.

We will also be "skeletonizing" it for weight reduction and increased surface area for inhanced passive cooling for the motor.

Below is a picture of the base part, more from our buggy in the coming days and weeks as we put it together and begin testing under power:




(edits for typos and photo posting correction)

HandyRacing

Discussion Link RE motors / gears / power / heat / maintenance and reliability:

(mostly Feigao and NEU but engineering issues apply to any motors)

http://forums.radiocontrolzone.com/s....php?p=2309019

(edit for typos)

ecocav04

i hate to break it to you but thats not a jammin x1 cr. i have no idea what that thing is

HandyRacing

The fellow above (helishack) who posted the pics is doing / the pics are from a separate project from the HandyRacing Jammin project.

Thanks for looking close enough to notice though. When we get our project / pics together there will be two projects being shared within this Post, hopefully more as we go along. Thanks.

helishack

Good eye.. Actually at the beginning of my first post (w/the pics) I let everyone know that I picked up a used XTM X-Terminator to try out the electric conversion. I noticed quite a bit of similarities between 1/8th scale buggies - so instead of experimenting with a costly model I thought I'd try this out on something that only ended up costing me ~$100.

I've been busy with international travel, but on my first opportunity I'm going to pick up a 100A+ ESC capable of up to 6S and a uBec (at the higher voltages I usually need one). Then I get to give it a run and start some gearing/power optimizations!

Regards,

Jeff

HandyRacing

Project Update I

Sorry for the delay, lots of things have been happening and its been tough to slow down long enough to write.

When we posted the original article, we were in the final phase of component selection. Batteries were in hand ( a pair of 7.4 volt / 4000 mAh with plans to wire in series for 14.8 volts), we had plans to implement our racing phase with an NEU motor but due to cost and time constraints we went with a Fiegao so we could get our testing platform on the track sooner. We expect the 4 pole NEU to be more efficent for battery life, run cooler, with more power than the 2 pole Fiegao. Stay tuned for this summer's racing on that part of the program.

The remaining component selection decision was which ESC to go with. When we found out the hi voltage cut out on the Traxxas VXL was around 12.5 volts it more or less became a done deal, no VXL, as it just wouldn't perform under the higher power we wanted - so we bought a CC Mamba Max. While the MM is rated to handle up to a 3 cell LIPO, its also known to actually handle 4 cell and even 5 or 6 cell LIPO voltages. There is the added (crucial) benefit of being able to program in custom throttle curve and breaking profiles, as well as LIPO cut outs.

( Editors note, maybe higher voltage at lower amps is less heat stress on motor / electronics? )

Once we were committed to battery / motor / ESC - the next thing was to pick up the steering servo (we went with a $30 Futaba high torque metal gear servo with ideas to buy a more expensive higher performance servo if needed for racing), we selected the Castle Creations BEC to run the receiver and servo and one cooling fan, picked up a couple of cooling fans from various sources and ended up running one fan (Integy) off the BEC to cool the bottom of the ESC (by drilling holes in the case) and a small Radio Shack 12 volt fan running directly off the battery to cool the top of the ESC (by blowing directly across the heat sink).

We went with an www.rc-monster.com heat sink / support bracket borrowed from a friend at the track to support the (known weak endbell) Fiegao motor, we still need / want to figure out a better cooling setup for the motor, design a fan mounting for a follow up.

We then had to actually figure out the precise wiring harness arrangement. As it turns out the way we mounted the ESC, receiver, BEC and connectors all to a custom made top plate running between the center diff to the rear bulkhead - it all ended up being a modular type arrangement so we could easily lift the entire assemblage away for service to the drive train. (See spur / pinion gear discussion).

We also went with bullet connectors for the (3) motor leads, and Dean's for the battery Y-harness and associated connections to the ESC (all this leaves us with a non-solder setup for quick turn around service and repairs on race day).

Up till the wee hours, we finally called it quits with a few remaining loose ends to deal with the next morning prior to practice / racing.

Up again a few short hours later, first thing in the AM after arriving at the track we charged our batteries, finished with last minute wiring and component connections, and powered up the rig.

No smoke. WHHHOHOHOHOHHO

We made our motor installation wiht a 12 tooth pinion mated to a 46 tooth Kyosho plastic spur.

First thing out on the test track we picked up a small stone and ripped ONE gear out of the spur by the roots.

Craptastic.

2nd time out on the track for testing, our pinion came loose and scored the motor shaft and pinion bore. We were able to clean the burry off the motor shaft and with a borrowed 11 tooth pinion we were back in action (we were unable to quickly clean out the bore of our 12 tooth pinion and had no backup).

We completed the first (5 minute) heat race, finishing with a respectable time / lap count - but more than anything SUCCESS with finishing the race - BOTH with a brand new rig, and with a driver who was driving it for the first time under race performance conditions. WAY TO GO.

2nd heat race, we stripped out the spur gear and didn't finish. 3rd heat race, came close to finishing, but again stripped out the spur gear and didn't finish.

Close inspection revealed we were having trouble getting close enough to the spur on our gear mesh adjustment due to our motor bumping into the chassis center brace. Apparently the difference between and 11 and 12 tooth pinion diameter was enough to obstruct our freedom of movement for motor / gear mesh adjustment.

To solve the problem we figured out a way to clean out the bore of the 12 tooth pinion and put it back in and were re-assembled in time for the main race.

Not only did we finish, but we completed the race with good time and on the lead lap with the rest of the pack (except the winner who got the extra time around for an 11th lap). OUTSTANDING.

I would love to take pictures, but the digital camera has gone missing and still not ready, however I do have a couple of blurry pics from race day via the camera-phone.

(I know, clear as mud):






Race results for those folks who want to see how performance under race conditions pan out:

http://www.rcproductdesigns.com/docu...%202-16-08.htm

HandyRacing

Summer 2008, MORL Jones event 1/8 Scale A-Main electric conversion race footage is here:

http://www.youtube.com/watch?v=Nq7xInqfpWo

helishack

Thanks for the video - and it's great to see that you're keeping the brushless 1/8th scale project and initiative alive. Your timing is great because I haven't done anything with this project since my last post. On Monday I received a KD36-60-08L 3000kv brushless inrunner. Wow, life is good I didn't do a speed test, but it's (obviously) a LOT faster and cooler than then Align 600L (1620kV) motor I had in it for the last few months.

With 3S2p 4400mAh available (2x3S1P 2200mAh), I only drew 1200mAh in 7minutes of run-time. This means I theoretically should be able to run for 15 minutes - but I do have to take into account that the batteries and motor will get hotter over time (and my tests were done during a cool evening in San Diego). After 7min the temps were checked and they were:

[ul][*] batts 98deg F[*] motor 119deg F[*] ESC 129 deg F (CC Sidewinder) - awaiting Mamba Monster
[/ul]

Btw, I used an eagletree datalogger to see my voltage, amp draw and cumulative mAh. My maximum amp draw was 36A - I could hardly believe it. I ran her hard, did a little bashing and a lot of dirt track + grass and street (speed) runs. I checked and re-checked the numbers and it was, indeed, a 36A maximum draw. I'm feeling very groovy about this...

After these great numbers and temperatures, I decided to hit up RC-Monster and ordered 15T and 17T hardened pinion gears (currently using 11T) Iit will be ~interesting~ to see what the current draw and relative speeds are like with the larger gears. I didn't realize the conversion could be THIS much fun - that 600L motor was definitely killing my speed (and fun). The steering servo arm stripped on me last night and ended my testing @ 7 min. I would have been pushing a bit longer than 7 min if I didn't have steering issues. Found a much faster and stronger metal-geared servo just sitting in my parts box (from a previous 600-class heli tail). Wow, she now steers strong and fast!

I should be getting my (10) A123 LiFePO4 (Lithium Iron Phosphate) batteries next week: 3S2P delivering 10.8v 4600mAh (or 3S3P delivering 10.8V @ 6900mAh). With the appropriate gearing and the fact that these batts can sustain 70A and peak at 120A (for 10 seconds), things should get REAL interesting REAL fast Last bit of info on these batts - they can safely be charged @ 10A, I've watched them charge @ rates as high as 22A. The 15-20 minute charge times are awesome... They don't puff or explode, they just get ruined if you do something you shouldn't have done. They also don't get out of balance very easily so balancing is good for them, of course, but not as critical as with LiPo's.

Jeff

p.s. I put a CC 10A BEC in case I overdraw the Sidewinder ESC's capabilities. My 5700kV HPI E-Firestorm on 3S LiPo absolutely requires the BEC or else the ESC will begin to exhibit thermals.

supermod

scrue brushless...lol..i love to rip

hrdcoreglf

Would you go see the Daytona 500 if all you got was fresh air and the whining of electric motors? How about Indy 500, or the Baja 1000. Smell and hearing are 2 major senses that electric just doesn't capture for me.

supermod

lmao

supermod

NITRO WILL NEVER DIE[>:]

helishack

When they're full-scale, nothing compares!

j

HandyRacing

Hey guys, How's the price of Nitro fuel lately?

(I hear China isn't shipping fuel this summer)

Al Gore's carbon tax kicking in yet?

HeliSchack - I hope to have further updates here soon..... In the mean time www.HandyRacing.com is live, I'm working on building it toward a tech resource for folks who want to do projects and find 1/8 scale electric conversions racing on tracks.

helishack

That's excellent news and I think you'll get a lot of traction given all of the interest in electric conversions (regardless of what some people may think). I'm sure we'll be seeing production EP 1/8 scale kits in 2009.

News flash... my A123 batteries showed up yesterday!! After I put my son to bed I dismantled the DeWalt battery case, separated the pack and got started on building my 3S and 4S packs. I decided to add the balance adapters at the same time (for the Astro Blinky A123 - the good folks at Astro have created a blinky balancer for up to 6S A123 cells - brilliant!). Btw, A123's don't go out of balance very much so I only ordered one of the balancers. After I built my first 3S pack I charged it up and hit the small track near me. I couldn't believe how much speed I didn't lose (A123 cells have slightly lower voltage than LiPo cells). Again, the datalogger confirmed that I was drawing a max of ~36A - sweet.

Tonight I'm going to finish the pack builds and run 3S2P 4600mAh for a head-to-head comparison with my previous 3S2P 4400mAh LiPos. For me the biggest plus for using the slightly heavier A123 cells is that in 10-15 minutes they are fully charged up and running again. With 4 packs I can run 2 in parallel for 10-15 min, then take the other two off of the charger for a swap-out. I can do this all day long... Charge off of a Pb battery (or two or three) all day long... It just depends on how long you want to run around in the dirt!

In case you're wondering, here are the weight differences:
[ul][*] 3S LiPo - 170g[*] 3S A123 - 233g
[/ul]
For my helis the weight difference is more considerable, but for buggys/truggies it's not as intense.

Cheers,

j