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Old 10-19-2007, 06:42 PM   #1
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Default Xray T2R, 2100 mah 2c LiPo, and Mabuchi power: Tech tips and Tricks

This is a project with the goal of taking down big prey like modified sedans with the equipment that’s least expected. I hope this thread will show that low budget, low weight, and a high degree of finishing skill can take the place of high dollar, high powered cars in a race environment. Some liberties will taken, when it suits me; at my home track we don’t weigh and we allow LiPo; check with you’re local club before trying some of this.

This is already a successful formula for me, because I have out-qualified (at least for one heat) a good driver that was using LiPo and the new Tekin R1/Redline combo. The great part about that was that it was only the first step, on the first carpet race of the season (for me), and it only gets better.

Initially I started with:
Xray T2R
Dynamite Tazer 12T esc
GreatPlanes Electrifly 3200 2 cell LiPo
Futaba s9550 servo
Spektrum micro rx
Mabuchi motor
foam tires
DNA body

If you’re counting, that’s a $40 ESC, an $11 motor and $80 battery. Later that battery was exchanged for a $42 battery. No $200-$300 investment in brushless/brushed gear, $200-$300 in batteries and their gear and lots of saved time too.

This combo came in at 1186 grams, which is very, very light. I have a goal to get the car under 1000g so as to have an unfair advantage in terms of power to weight and handling.

The next step was to take out the GreatPlanes LiPo because at 190g, it was just a pig. For comparison, a normal 3800-4200 NiMH pack is 360-400g+. The new pack that has shown itself to be a winner is the FlightPower EVO LITE 2100mah 2 cell LiPo. It only weighs 106g and is a little longer than a NiMH 4 cell pack and much narrower. For some perspective, this would be a good pack for an Associated RC18T/B/R car, and never considered for 10th scale. This about getting crazy light though and the low draw of the Mabuchi will make this work.

Balancing this took very little work, and going along with the light theme, no chassis weights are used. The AMB transponder and Spektrum rx are tucked up next to the steering rack on the right side of the chassis opposite the servo. The Dynamite ESC is right behind those, followed by the LiPo sitting over the back four battery slots. Only the Mabuchi and the servo live on the left side of the chassis. When the car is on the tweak station it takes very little weight jacking with the springs to level it out.

Also changed was the Mabuchi motor. Earlier in the year, I got the club to purchase 20 Duratrax 540 motors very similar to Mabuchi’s. It looks just like a Mabuchi except for fan blades attached to the top of the stack to cool it. The hope was to make this a handout motor for Novice and maybe even stock class type racers. This did not work out though because the motors do not fit without modification in JRXS and TC4 cars that currently make up most of those entries. Anyway, after testing on the cheeseball dyno, I guessed that this motor was actually faster than the Mabuchi

In the second week of racing I chose to maximize track time, and race in stock/rubber and modified/foam. To make this work with a short race schedule the rubber tire setup stayed on the car the entire time. This combo was top qualifier by 3 laps in stock, and 3rd qualifier in modified by 1.5 laps. No follow through though, because I left early for a previous engagement. The Duratrax motor was fast, fast, fast, only the guy with the Xray T2/fresh 4200’s/LRP ESC/4.5 motor was much faster.

Next week I will race modified/foam only class to take advantage of the foam tires. The rubbers weigh in at 122g while the foams are 69g. That’s over 50g of rotating, unsprung mass, and the car will be much faster for it. Also, I’m going to take Protoform lightweight Status carpet body and paint it with a very thin coat of paint to try to eke out some more grams.

Please feel free to ask me about it, and tell me what you think.
Gary

Last edited by gacjr0; 10-20-2007 at 08:19 AM.
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Old 10-19-2007, 07:30 PM   #2
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I actually watched the first heat this car raced in and it won in the mod class. I also raced agianst it in the Stock class and it pulled harder than any silver can motor had a right to be pulling

Got to hand it to you Gary. I am amazed at how that thing runs.
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Old 10-20-2007, 08:18 AM   #3
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Thanks, Scott. I love this thing! To be fair, in modified I only won that one heat. Read the silver can tips/tricks thread, to learn some of the power tricks for these motors. I only did a couple little things to the one I have so I might ask to buy more from the club.

Other resources:
XXX Main turing car setup guide
Xray's tuning guide
the stock motor thread
the xray threads
rubber/foam flamewar threads
LiPo/NiMH flamewar threads
John Stranahan's threads

if you can filter out the garbage in the flamewar threads, there is actually a lot to learn.
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Old 10-24-2007, 12:09 PM   #4
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Xray T2R,  2100 mah 2c LiPo, and Mabuchi power: Tech tips and Tricks-t2r-mod.jpg  
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Old 10-24-2007, 12:39 PM   #5
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Cool project, less weight is better for everything, tire wear, parts breakage, you can't be that might heavier than a pan car setup.
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Old 10-24-2007, 01:32 PM   #6
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thats cool! i had a 1/14 rally that weighed 918 grams, and you've almost hit that already in 1/10! i was looking for unnescasary weight on the picture... not a thing! you've really stripped that car down! are you allowed holes in the body? you could drill a grid of holes in the body just to make it a bit lighter. i don't know how much of a factor aerodynamics are though.
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Old 10-24-2007, 03:57 PM   #7
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Wiffle Car! LOL

No, the lightweight body is already really flimsy.
Next, I'm thinking aluminum or titanium screws and tie rods and graphite chassis/towers.
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Old 10-25-2007, 08:37 AM   #8
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Quote:
Originally Posted by gacjr0 View Post
Wiffle Car! LOL

No, the lightweight body is already really flimsy.
Next, I'm thinking aluminum or titanium screws and tie rods and graphite chassis/towers.
wiffle? thats a new one...

titanium is good, although i don't really like aluminium. give me steel any day.

actually, to save weight on my rally car i have a 2 cell Li-ion pack from an old media player (what a load of crap that was). more capacity than the stock pack AND weighs a 5th of the weight of the equivilant ish nicad. 1200mah 7.2v nicad (liberated from an old drill) - 250g 1000mah 7.4v li-ion (liberated aswell ) 49g its a no brainer
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Old 10-25-2007, 09:18 AM   #9
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I think this kind kind of thing is important because it shows how we can reduce cost and weight without losing performance and reliability. Also, the stresses on the battery, motor, ESC are way down.

I bet your car went much faster with that Li ion pack in it, what did you recover it from?


"She did it like this, she did like that, she did it with a wiffle ball bat soo....."
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Old 10-25-2007, 05:10 PM   #10
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LOL...I've been running a T2 with Lipo and a Mabuchi in the local parking lot races for months now. It works really well.

I run against "regular" stock motors (27T and 13.5) and I usually do pretty well. It's definitely not faster on the straight or anything, but I can generally beat people bad in the infield, because I can carry so much corner speed (at/near WOT the whole course. ).

Good job!
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Old 10-26-2007, 02:23 AM   #11
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Hello, we here also race with mabuchi for endurance, what is the final ratio that you use for lipos? Thanks.
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Old 10-26-2007, 06:03 AM   #12
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Currently running 5.95 with rubber tires for a 33.3mm rollout.
5.38 with foam tires.
This is a very small track.
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Old 10-26-2007, 06:09 AM   #13
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Quote:
Originally Posted by gacjr0 View Post
I think this kind kind of thing is important because it shows how we can reduce cost and weight without losing performance and reliability. Also, the stresses on the battery, motor, ESC are way down.

I bet your car went much faster with that Li ion pack in it, what did you recover it from?


"She did it like this, she did like that, she did it with a wiffle ball bat soo....."
i havn't got a charger for it yet, and no RC gear for the car, but i tested the motor quickly with the pack and it ran pretty well. it was from a mustek media player, which was a box with a hard drive, a screen and a battery. it sucked to say the least. so when the hard drive cable died i liberated it. it's the size of a match box, it's brilliant!
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Old 10-26-2007, 03:43 PM   #14
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my LHS stocks these. what do you think? seems almost identical to your pack infact! (except with UK style pricing - 2x the price)...

http://www.e-rc.co.uk/shop/evo-1800mah-3s1p-p-61.html
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Old 10-26-2007, 03:43 PM   #15
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my LHS stocks these. what do you think? seems almost identical to your pack infact! (except with UK style pricing - 2x the price)...

http://www.e-rc.co.uk/shop/evo-1800mah-3s1p-p-61.html

i want 3 cells because its the closest match i can get to 8 cell btw.
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