EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poof!!)

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Wookiee
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EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poof!!)

Post by Wookiee » Mon Sep 14, 2015 5:30 am

Hey everyone,

Does anyone know if there is a motor limit to the EVX-2 depending on what Lipo pack you are running (kinda like the Axial AE-5 has a certain motor limit for the ESC when run on a 2S compared to when run on a 3S).

I was bashing around the Clod the other day on a single 3S, went through another 3S then hooked up a pair of 2S Lipo's to give that a go for the first time (there was a 5 min break or so between the 3S and 2 x 2S packs). When I started to use the 2 x 2S packs it seemed like there was some lag or speed issue. At the time i put it down to the rims might be spinning on the tyres as I hadn't glued the tyres and rims together I was using the elastic band trick to make the tyres and rim grip a little better.

Anyway, I increased the throttle to full to see what kind of speed I would get and very shortly after I heard a "poof" a bit of bluish smoke and that dead electrical smell.

Looking at the damage so far all I can tell is I fried a motor or broke a motor as it now makes a clicking noise when the one axle is turned. The EVX-2 doesn't seem to be showing any signs of "Kaboom", the LED light illuminates when it is turned on but until i strip the motors out and put the stock cans back in, for now, I'm not sure if I have damaged anything else with the full 14.8V on tap.

I can't find anything so far that says the EVX-2 has a particular motor limit depending on battery voltage being used. I can only find the generic turn limits for a 540 or a 550 motor.

Andy is probably the best man to provide some insight on this...

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by mavrick0 » Mon Sep 14, 2015 1:40 pm

You over voltaged the motors. The EVX should've been able to handle those motors and power fine but the motors themselves are probably both dead, the only thing is if a motor shorted that could've done in the EVX. A standard 540 can motor is only really designed to handle a max of 8.4v and even that is pushing it. Anything above that will drastically reduce their life.
A off roader may be able to jump and run around a track. A on roader may be able to run circles around the road but a monster truck will run over anything and everyone.

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by shadowfocus603 » Mon Sep 14, 2015 4:48 pm

Andy found as well that the Firebolts are not zero timing motors no matter what is claimed and the rear motor will :explosion: very quickly. On my clod I was running a set of Revo Titan motors. One of which specifically said Reverse Rotation and everything worked great. I was running 17t pinions and the truck was scary fast on 16.8v.

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by Sixtys Guy » Mon Sep 14, 2015 8:42 pm

If you had just run two 3S packs, then I reckon those motors would have been red hot. then put more voltage into them I reckon they just gave up!

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by shadowfocus603 » Mon Sep 14, 2015 9:45 pm

He ran on a single 3s presumably with a jumper on the non BEC plug then went to dual 2s. One thing I have heard is that the BEC in the EVX-2 doesn't like more than 8.4v so that may be a culprit if it isn't the motors.

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by andymac0035 » Mon Sep 14, 2015 10:31 pm

Oh wow, firebolts on 4S.... they lived up to their name. :explosion:

Lets see where to begin here,

The EVX-2 esc does not care about 3S, I've run a single 3S pack through the main (bec-side) plug on both the newer lipo-ready, and older EVX-2 on many ... many... I mean a LOT.... of occaisions with no issue. I actually think you get more power at the bec this way, but I can't confirm that one.

The firebolt is happiest on a single 2S pack, but to say all 540's don't like 3S is incorrect. With stock gearing, the stock silver can motors will run 3S happily all day for a long time. Now if you gear the stock motors up, that will be too much load, and then they will indeed fry, but it will take a few runs. With stock gearing the silver cans will even take 4S for a little while, but again, not for long. My average was four runs.

Firebolts will run 3S with stock gearing, but they will also wear out fast. 5 runs was about what I averaged, you might get more if you are conservative.

Now, if you are racing, and just hitting it for short runs (read less than a minute), then that's different.

Back to the issue of what happenned:

You ran firebolts for 2 runs at thier limit (technically beyond), and then ran them (waaaaaaay) beyond thier limits. :explosion:

EVX-2 is probably okay unless you shorted something.

If you can fit titans, I would try that, otherwise, go with stock motors and stick with 3S.

Hope this helps you some.

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by Wookiee » Wed Sep 16, 2015 7:32 am

Thanks for the feedback guys. Wow I didn't realise I'd go through the brushed motors so quickly on 3S and 4S. They weren't new motors either and had done several runs on NiHm packs. Also it has been raining down here in Perth so the place I was bashing around was nice and wet and muddy with some large puddles to run through. That probably also didn't help the situation. :?

Shadowfocus - Yep you're correct I ran single 3S packs with a jumper on the non BEC side of the ESC before plugging in the 2 x 2S packs. I think from recollection it is actually the front motor that went....although in saying that i think when i installed the 14" links i accidently swapped the axles around so the back motor became the front motor so in that case it was the rear motor that went which falls in line with Andy's findings that the Firebolts are not true 0 timing.

Looks like the old stock can will be going back in and hopefully last a little until I can get some 550's.

So Andy, will the Titan 550's hold up better with 2 x 2S packs or is it best to avoid 4S power even if I upgrade to 550's? I WANT 4S POWER!!!!! :twisted: :twisted:

Also before someone says brushless....I am on my way to brushless but being a noob with RC's I'm working my way up to it so I can handle the additional speed and try to avoid breakages as much as possible.

Thanks again guys, really appreciate the feedback

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by Wookiee » Wed Sep 16, 2015 7:39 am

To be lazy...I can't recall if it is the Titan 21T 550's or the 12T 550's???

Edit: I think its the 21T ones isn't it??

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by MI_Ghost » Wed Sep 16, 2015 11:18 am

Wookiee wrote:To be lazy...I can't recall if it is the Titan 21T 550's or the 12T 550's???

Edit: I think its the 21T ones isn't it??
You want the 21T Monster 550's
TRA3975 (E-Maxx, E-Revo)
TRA3975R (Reverse Rotation)(E-Revo)

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by Wookiee » Wed Sep 16, 2015 1:18 pm

Thanks Ghost

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by andymac0035 » Wed Sep 16, 2015 9:51 pm

Yup, those are the right titans.

I do need to point out however, that unless you are also planning to gear those up, you are kinda' wasting your time and money.
Stock motors on 3S = 16 mph
titan 21T on 4S = 17 mph

However, I run adjustable motor mounts on my truck and the stock 13T pinions have been replaced by 19T pinions..... and that translates to speeds of 25-27 mph.
It also means a lot of you-know-what if you get out of hand.... :explosion:

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by Wookiee » Fri Sep 18, 2015 3:02 am

Cheers Andy,

I'll look into some 17 or 19T pinions to gear up the donk (Aussie term for motor :wink: ) when i get the Titan's. Fortunately I have the old stock cans to run with at the moment and a spare Clod sitting in a box with 2 brand new stock cans to throw in to keep me going.

Ohh tell me about the :explosion: . I need to put a little more weight in the rear of the Clod chassis to stop the front end tipping forwards too much over jumps (will need to revisit my fabricated 3-4mm thick aluminium bump/skid plate I made up). So far I've done quite a few summersaults on landing after the front tips forward too much. The stock Clod body is not looking too good at the moment :twisted:

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Re: EVX-2, 2 x 2S Lipo's & 15T Firebolts (something went poo

Post by MI_Ghost » Fri Sep 18, 2015 4:54 am

Wookiee wrote: I need to put a little more weight in the rear of the Clod chassis to stop the front end tipping forwards too much over jumps (will need to revisit my fabricated 3-4mm thick aluminium bump/skid plate I made up). So far I've done quite a few summersaults on landing after the front tips forward too much.
It would be far easier to adjust your driving technique than to start down the path of the weakest link.
A tiny 2oz pebble dropped on your toe might barely be felt. A 2lb stone is probably going to hurt. Adding weight is that much more for the suspension (springs/shocks, axles/tires) to absorb on landing. Adding more weight to counterbalance jumps will eventually start causing damage on landings.

You can learn how to correct an unstable flight by applying a touch of acceleration, or braking to adjust a front low/high condition. Those 4 monsterous gyroscopes attached to the end of the axles will easily pull the front up with a slight tap of acceleration. If the front is to high. A slight tap of the brake will cause the front to come down. The critical part in all of this is to make sure that you are not on the acceleration or braking when landing. You want the wheels to be close to freewheeling. Landing on acceleration or braking will cause the alignment pins on the back of the wheels to shear off as the torque from the axles is suddenly forced to start or stop.

Weight is the enemy of jumping. If it goes up. It will most certainly come down again. If you must add weight. Do it in a manner that reenforces, and strengthens the parts (axle hub stiffeners inner/outer. axle trusses, Etc...)

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