Failsafe help

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K

kmanmx

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Hello,

I am new here and received my HPI Savage X 4.6 a few days ago, i've broken it in and tuned it properly, and i've installed an M-Tronics micro failsafe and a fuel filter + primer.

I am having problems with the failsafe though, to try and debug the problem i put 4new quality Duracell AA batteries in the battery holder, connected the fail safe and fired the engine up, all was fine for about 1/2 a tank - but after that if i hold full throttle for more than half a second it simply cuts out and the throttle servo returns to neutral, i have to go over and turn off and back on the receiver, and then it does it again. I am not quite sure why, this is my first nitro truck and this is all pretty new to me - i only got this far from extensive reading on forums like this ! but i can't figure this out. It also occasionally does the same if i brake hard, but not much.

While I'm here i'll ask another unrelated question, i am having trouble setting up the brakes. At between 20 to 30mph it takes a full 20 to 30feet to stop, the brakes definitely work, but they are far to soft for my likeing. Even at low 5 to 10mph speed it takes 4 to 8 feet to stop. I am not sure whether i've adjusted it badly or the servo doesn't have enough power to pull on it properly (If i pull on the brakes manually, they are very strong)

Any help would be appreciated.
 
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Welcome to the forum!

I think your problem is with your batteries. I am not sure how long the 4AA usually last, but get a hump pack. Your fail safe is probably detecting a low voltage condition which is why its cutting out the throtle servo. hump pack is one of the best investments to make when you start out in this hobby. A hump pack will give you 6.0v instead of the 4.8 you get from 4 AA's. the higher voltage will give you more power for your servos, and longer run times.

For your brake question, there is a plastic thumbscrew on the end of the brake linkage arm, screw that in until you get the brakes where you want them.
 
Great, ordered one now.

This hobby is so expensive. I only spent £380 on the savage yet somehow i have spent £580 in total already.. only had it 3 days.
 
I think it could be the AA Duracell's too.

When i got my savvy new i got a load of new Duracells from my local newspaper shop, put 8 in my Tx and 4 in my Rx battery holder, flicked the Rx power switch on, nothing, dead as a doornail, put another 4 in, the same so i called my LHS where i got the truck from and he said that probably the batteries are no good, apparently there are dodgy batches of Duracells going round the UK (i assume u are in the UK cos of the Modelsport UK link) that come out the pack nearly dead.

So i got some Energiser rechargeables, charged them up and problem solved, i now use a 6v hump pack which is much better than 4 AA's though, highly recommended, i got mine on eBay for about a tenner posted.
 
Well i've tried 4 sets of batteries and the failsafe goes weird with all of them after a half tank maybe a full tank. I've tried Duracell's, Energizers, Sainsburys own brand and some rechargeable AA batteries.

Anyway I've ordered a 1500mah hump pack, how long can i expect it to last before i recharge ?

And nope - no pictures of the savvy yet. It's totally stock except the fuel filter, and i never even put the body shell on because it's too much effort, i'd rather just drive and have easy access to the engine etc. I might take some soon though, after I've cleaned the grass out of it. The failsafe is annoying me now.. i just drove down my street and it decided to switch off, i crashed into my wheelybin at 30mph. Naturally being a savvy though, nothing broke :happy:
 
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Ok, well hopefully when you get your hump it sorts it out, if you ordered today you should get it monday, iv ordered stuff from Modelsport and theyre pretty quick.

I use an 1800mah hump pack and i get a good couple of hours, on n off, run time from it, but iv never actually had it die on me and had the failsafe kick in yet and i have done a gallon in one afternoon a couple of times without the hump dying on me though that may change now I'm running 2 digital servo's.
 
Sounds great.

Yeh i ordered using express delivery, just been dispatched - so hopefully monday.
 
Cool, yea you should defo get it by monday, i order using standard delivery from Modelsport, if i order early enough il get it the next day, if not the day after, so using express maybe even tomorrow!

With that hump youl need to change the stock switch over to the supplied switch because the batteries futaba type connector wont fit into the BEC connector on the stock switch lead, but if you don't fancy doing that you can get an adapter and use your stock switch, my hump didnt come with a switch so thats what i had to do. http://cgi.ebay.co.uk/Futaba-Female...d_JN?hash=item5ad12fcfb5&_trksid=p3286.c0.m14
 
I'm sure i will figure something out. Its shocking how long normal branded batteries last. Energizers best lasted a mear 1.5 tanks before the brake and steering became too slow.
 
I had a similar problem with a duratrax failsafe. When I gave my truck throttle it would brake immediately, and then reset. I could give it super light throttle and it would not do it but if I gave it more than a tiny bit it would set off the failsafe. Once it stopped the falisafe would reset itself. What could cause this? Also it only has a problem when the engine is running. I noticed when I would turn the mill over it would tweak out like there was some interference each time I hit the button on the rotostart but then once it started it would idle with no issues. How would just the motor turning cause this interference, and why would it be fine at idle but not when on the throttle?
 
Yeh they can be a real pain. When i get the new hump pack i will tell you if it improves. also make sure you use quality batteries.. i tried some no name ones and the servo barely moved!
 
I received the battery pack ! it says standard charg @ 150ma will take 15hours. But i have a charger which will charge up to 2amps. What do you think i could charge it at without damaging it ??
 
I charge mine @ 1amp, takes about half hour, i wouldnt charge @ 2amps, if your charger will charge at 1.5 or less then use it, otherwise id use the wall trickle charger.
 
Okay thanks. I'll charge at 0.7amps for now, so i will see how it goes.
 
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Cool, I'm not 100% sure, but i think the general idea is you can charge safely up to the mah of the battery, e.g if you have a 1500mah battery you can charge up to 1.5amps, preferably a bit less, 2000mah battery up to 2amps and so on.
 
Yeah the term is 1C. To charge my 1200mah batt at 1C it would be 1.2 amp charging rate. To do .5C it would need .6 amp charging etc. Don't charge over 1C it's not good for the battery. My stock XL 1200mah takes about 45 minutes to an hour to charge at a rate of 1 amp which is a little under 1C for that size battery. It doesn't hurt to charge slower, some people always charge around .5C but I have never heard of anyone having problems charging at 1C with anything other than lithium based batteries and even then I think it is rare to have problems at 1C.
 
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My 3000 mah for my rotostart gets charged at only 2 amps when I could charge it at 3, so I'm on the safe side and it still only takes about an hour or maybe a little more.
 
Okay, well charging the batteries for my rotostart isn't a problem, a 2000mah pack lasts me fine. I am only putting between 4 and 8 tanks of fuel through the savvy each day and the rotostart is fine with this, so i can just charge it over night.


Well i temporarily fixed my fuel tank so i can test out the hump pack. The throttle and steering servo's definitely like the 6volts.

However.. my fail safe still doesn't like me holding full throttle for more than half a second. If i do i lose all control of the throttle servo and it returns to neutral for about 2 or 3 seconds, and then it lets me carry on. I can hold 95percent full throttle forever with no problems. So why not 100percent full throttle ?

It's getting annoying now.
 
I had this exact same problem with mine only I could hardly give it any throttle before it would cut out then reset. I'd really like to know the cause of this. I think it is the truck, not the failsafe, as I unplugged mine and then had a runaway. This problem seemed directly linked to the motor turning over because my failsafe would tweal out when I used the rotostart too. Weird and very annoying. I cannot figure out why the motor would cause this interference!
 
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