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  1. #1
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    Nub Gearing Question and some reliability questions

    Hey all,

    Very much new to the RC world, and bought my 7 yr old son a Slash with the Titan 12T about a month ago. Saw how much fun he was having and bought myself one too A month and 30 battery packs later, we've grenaded two 12Ts. I'm not sure if it was heat or trash that did them in, but I've decided to upgrade both trucks to Velineon 3500s and take care of any trash issues we may be having. We run on a packed dirt track that I built for us, but it can get a fine dust on it when dry, so the cars are working fairly hard. Certainly harder than pavement or the packed clay tracks I see on YouTube.

    Anyway, long story short, I want to select gearing for our trucks that will keep approximately the same top speed, while reducing our temps well below safe levels. I'm after absolute maximum reliability until he gets older, then we can think about boosting his speed more when hes paying for his own repairs And I don't want to replace another motor anytime soon.

    So the way I understand it, the Titan 12T is a 3100kv motor, so with an 8.4V battery, it would be turning ~26,000 RPM (assuming perfect efficiency, which its not. Probably closer to 24,000 RPM?) And the Velineon 3500 would be turning around 29,400 RPM (again, perfect efficiency, so probably closer to 28,000 RPM?)

    Our Slashes are 19/90 geared from factory, so I'm thinking with the Velineons extra RPMs, I have to drop my pinion size down quite a bit to keep the same approximate top speed, right? Probably to 16 teeth?

    Since the Slash VXL is factory geared at 23/86, I'm thinking that at 16/90, we shouldn't have a single worry about heat (I'll bring my heat gun from work to be sure)? How about at 19/90 or 19/86, should we decide we need more speed?

    With the gearing taken care of, I now need to look to other things to do to take care of reliability. We're up here in the boonies, with the closest hobby store being hours away, and most mail order being at least 4 days away. Thus far I've ordered Boca bearings for both (sons Slash got dunked and he'd having some bearing issues now), a spare trans idler gear, a spare transmission, aluminum STRC rear bearing carriers, ProLine Powerstrokes (for his anyway, since a cap popped off and he lost the rubber seal), RPM front a-arms and aluminum caps for my shocks. Probably get some RPM rear arms too and a couple aluminum bell cranks. What else do I need to consider having around?

    Thanks in advance for any help, and I look forward to continuing with this forum. Also apologize if this has been covered before, but a quick search didn't really net me any results.

    Rod

  2. #2
    RC Turnbuckle Jr. 08kgraves's Avatar
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    ok well i can tell you this much from experience. im new to slashes as well and here are the things ive learned so far.

    i myself bought a brushed roller and then put on a vxl brushless motor/esc on it. not realizing that the gearing was different since i have an xl-5 manual not a vxl manual i thought the stock gearing was 19/90 so i went out and got a 19t pinion since it did not come with it. it came with the 90t pinion installed and the 86/23 (high speed, road only gearing) in a bag. well after running and learing i can tell you that on an 8.4v nimh battery that 19/86 or even 20/86 will be plenty safe since you already have something in that range.

    i dont know if its just my nimh batteries (really old, given to me for free) but 23/90 gearing didnt overheat my motor or anything close but my battery got up to like 167 degrees! not good. so im thinking they may be toast just due to old age.

    i called traxxas and found out that the brushless motor can safely run at higher temps just do to the design. so if you want to play with the gearing keep the motor below 170 degrees according to traxxas and they didnt give me temp for the esc, but the cooler the better. mine was running at 108 when my battery was 167 which is probably a pretty safe range. oh my motor was only at 120 max with any gearing ive tried even the 23/90. it was around 114 with 20/86 though. also you can pick up a esc fan just to be safe that clips right onto the vxl speed controller and just plugs right into the little red lead coming out of it.

    as far as other upgrades:

    get aluminum caster blocks! one good hit and off goes your wheel, just happened to me the other day. waiting on mine now. broke my rear shock tower first time running as well so aluminum towers wouldnt be a bad idea at all either. spare bearings are good, and maybe just some little spare parts like wheel nuts, driveshafts, just little cheap things in case something does go bad. maybe an extra slipper clutch or something.

    hope this info help you out. feel free to look at my build thread for some of the things i have done/plan on doing. i have videos up as well in there.
    there's no life like a LOW LIFE!
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  3. #3
    RC Turnbuckle Jr. O.G.'s Avatar
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    Welcome to the forum.

    18/83 or 18/86 would be a good place to start. You may still have some temp problems but you won't know until it's up and running. You don't mention lipo's so I'd recommend going with a couple for your trucks, minimum size I'd buy is a 5000mah 25C 2s lipo. If that setup is still too fast for your son, you can put the esc in training mode until he gets used to the speed. I usually break the bearing carriers so you may want to pick up an aluminum set (STRC makes great alu parts).
    My Black & Blue Rally is faster than your color...

  4. #4
    RC Turnbuckle Jr. 08kgraves's Avatar
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    yeah, lipo is where its at. only problem is then you need a good charger as well. but i actually run that exact size mentioned and have had zero issue with it on a 20/86 gearing. and i have to agree about strc, thats where my rear shock tower is from, and thats where my caster blocks are coming from as we speak. another good thing about lipo is that they charge faster than nimh batteries and they dont slowly die off till your just putting around. they run full bore until there dead then you throw in another. so not only do they charge faster, but they last longer per charge, more efficient per charge, and they give more punch then nimh batteries as well.
    there's no life like a LOW LIFE!
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  5. #5
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    Thanks for the info guys. I've lipo'ed us up with an Onyx 5000 mah 25c and a Traxxas 7600 mah 25c. Bought a Venom ProCharger first, then realized that it wasn't going to keep up with 3 RC cars in the house (also bought a Rustler off eBay for my 6 yr old), so I bought a Duratrax 245 as well.

    I'll order up some front aluminum carriers (have the rears already) and caster blocks today. I've got a bunch of spare hardware already, so I should be ok there.

    I'm sure I'll be bugging you guys more in a bit. I've had to learn quite a bit so far, and wish I'd bought the VXLs right off the start, but live and learn

  6. #6
    RC Turnbuckle Jr. 08kgraves's Avatar
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    i almost didnt buy brushless off the start myself, but im so glad i did. and yup i just bought my second onyx 5000mah 25c 2S lipo the other day, great battery for the price. never used it but i hear that duratrax 245 is a good charger. as for the venom, no clue never looked into it. i can tell you that my next charger will probably be the hitec x4 ac plus charger. it does 4 batteries at once right now i just have a cheapo thunder ac6 charger. it was cheap to get me going though.

    dont know what you have for hardware but look into tony's screws. there the best you can get!
    there's no life like a LOW LIFE!
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  7. #7
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    do u have stock wheels and tires?
    Slash 2wd Vxl, ERBE; Crash N Learn

  8. #8
    RC Turnbuckle Jr. 08kgraves's Avatar
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    yeah stock tires suck especially on any sort of track, but thats something you can easily order. oh if you notice that in corners your car tries to diff out (inside wheel lift slightly and spin way faster causing you to slow down) put some heavier lube in the diff.
    there's no life like a LOW LIFE!
    Drag It!

  9. #9
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    The Duratrax is a much better charger than the Venom. I had to play with the Venom to get it to charge right up to max (sensitivity settings), and it still doesn't want to charge the 7-cell Dynamite hump pack for the Rusty, but I do wonder if I used the temperature probe if it would be better. I was actually going to get the Hitec unit, but my lhs doesn't carry it and the online place I buy from was out of stock. Now I think I'm going to be plenty happy with the Duratrax.

    And yep, stock wheels and tires. Was looking into other options, but I've kinda spent the hobby budget for a bit so we'll have to make do with the BFGs for right now.

    And there is plenty of slowing down in corners, but its tough to keep your speed up when skidding along your roof....

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