What Power For My Hotshot?

[Percymon]

Almost finished the Hotshot restoration and all i have is an old silver can...

Bare bones i'm going to need a ESC and a motor - i have a mtroniks sport auto 20 coupled to an ansmann clash 23T in my manta ray, and to be honest it goes pretty well to my eyes, and certainly quick enough when running outside the house and the local school car park, with its speed humps and kerb stones, lovely 4 wheel drifts on damp tarmac.

I've no idea how the gearing compares between the manta ray and the hotshot, but given the larger wheels of the hotshot i'm guessing i need a bit more torque / power to see similar performance ?

I know i can replicate the manta ray set up for around £25, or go with the same ESC and a Tamiya sport tuned or Dirt Tuned motor for £38-45, which may well be enough for my needs.

However i'm wondering about brushless, some combos are around £80 in the UK now, and maybe £60 imported. I have no idea of kV and how this relates to speed / torque / turns of a brushed motor, so could someone help me out..

is high kv good for speed and low kv torque ?

what sort of kv would suit the hotshot ?

I'll be using 5000mAh Vapextech NiMH packs, and have no plans for LiPo.

Thanks

[Butler]

£40 will get you the entry level EZRun 4300 ESC and Motor. Well worth it. I jumped from a Superstock RZ to it and the speed improvement was impressive and I don't think I lost any run time either.

[Percymon]

£40 will get you the entry level EZRun 4300 ESC and Motor. Well worth it. I jumped from a Superstock RZ to it and the speed improvement was impressive and I don't think I lost any run time either.

Thanks for that - looks like i'd possibly have issues with battery power ? My Vapextech NiMH are rated at 35A max current, and if this table is anything to go by...

EZ Run Specs

Specifications Cells RPM/V [Kv] Idle Current [iO] (Amps) Resistance [Ri] Max amps

C40-09S 2-3 lipo/6-10NC 4300 2.4 0.0119 45

C40-10S 2-3 lipo/6-10NC 3900 2.2 0.0148 40

C40-11S 2-3 lipo/6-10NC 3600 1.9 0.0179 38

C40-12S 2-3 lipo/6-10NC 3300 1.6 0.0213 35

C40-13S 2-3 lipo/6-10NC 3000 1.4 0.0248 32

C40-14S 2-3 lipo/6-10NC 2800 1.2 0.0288 30

then the 4300kV draws 45A current , and i'd perhaps be better off with a 3300kV ???

Also a 4300kV will run to 31000rpm based on 7.2V stick pack, in which case does that infer its not very torquey and will have high top speed but lacking in acceleration ??

Sorry if i'm being stupid here, i've only just realised kV x battery volts = rpm !! DOH !!

[Butler]

35A, is that continuous or burst?

I am sure your battery is better than some of the 3000MaH cells I use with mine. Never had issues. Some people get stuttering, but if you turn the punch settings down, then its fine. The punch is at max by default.

Worth a read...

http://www.tamiyaclub.com/forum/index.php?...17&hl=ezrun

[Percymon]

35A, is that continuous or burst?

I am sure your battery is better than some of the 3000MaH cells I use with mine. Never had issues. Some people get stuttering, but if you turn the punch settings down, then its fine. The punch is at max by default.

I'm assuming thats continuous as a EZRun 3300kv system i found on ebay quotes 35A continuous , 190A burst.

Thena gain the 4300kV combos on ebay still use a 35A esc, so i guess i'm worrying about nothing !

Good to hear you have no issues with NiMH. I'd be turning the punch down anyway to protect the gearbox internals - i don't fancy dismantling the hotshot drivetrain too many times !

[tamiya monkey]

i have a 60amp/8.5t ezrun system fitted in my slash, i ran it on vapextech nimh packs from 3300-3700mah and found it ran fine, ive since moved to lipo and wouldn't go back, but if you were worried about running nimhs, dont be.

i would say an ezrun 35amp esc and either a 9t or 13t would suite the hotshot, im sure you will be happy with the results for about the same money as a brushes setup.

[Percymon]

I read all 13 pages of the thread linked to earlier in the thread and found one reference to the Hotshot which said the 9t 4300kV was too much for the front monoshock suspension (i know its a weak point anyway but i want to retain original looks). Found a few references to Manta Rays, one of which blitzed its gearbox but everyone uses and abuses differently i guess

I'm tempted to go safe and just buy a Modelsport uk sniper RV-12 ESC (£22) and a LRP V10 spec 5 19x2 motor (£24), but badword thats as much as the EZRun system - my trouble is i don't like waiting for stuff - 3 weeks from HK would kill me !!

[tamiya monkey]

1 its worth the wait believe me and 2 i normally get my stuff within 2 weeks, but i know what you mean, theres nothing finer than just going and picking something up.

i would say wait and get the brushless system ordered lol.

[Percymon]

I have - woohoo !!!

ebay Item number: 290487264128

Lets hope postal service is quick, albeit doubt they'll process my order til Monday now. I ordered 2 bearings from dinball around Xmas time and they came through in under 3 weeks, so i have my fingers crossed for this combo !

48.96 Euros , somewhere around £41 so can't complain (cheaper than the LRP V10 17x2 motor and mtroniks RV-12 ESC i was tempted by !)

[mike_o]

Just a quick power dissipation aspect: If you run a motor at 7.2V and 35A continous, then the power dissipated in the motor will be (100-"the efficiency") x 7.2V x 35A. If the efficiency is 90%, you'll get 25,2W (VxA) of dissipation in the motor. If that's really continuosly, your poor little motor will heat up quite significantly. And, if somehow the real life efficiency is closer to 80%, then you get a whopping 50W of heating in your motor! Better provide cooling :-)

But of course, we don't run continously 35A, I assume.....

Edit: Hmm... If you'd exhaust a 5000mAh stick in 30minutes, then the average current would be roughly 10A. Doing it in 15 minutes would mean you'd drawn an average of 20A. My packs last for more than 30 minutes, but I mainly drive lean, 2WD buggies. What's your experience?

[Percymon]

I mainly drive lean, 2WD buggies. What's your experience?[/i]

Bashing on a damp football pitch and neighbouring tarmac/gravel area i get over 30 minutes from a fully ball raced 4WD Manta Ray which has smaller wheels than the hotshot and is only equipped with a 23T Clash motor - thats from the Vapextech 5000mAh battery pack.

I'd hope the increased efficeincy of the brushless syetm will cancel out the wheel size effect, but then the motor takes more power. 20 minute run time , requiring extra concentration !, will be more than enough for me.

I'll go armed with a few extra packs - trouble is my son will not be impressed by his new Rising Storm being trounced lol!!. He's none too happy about the Manta Ray, with its £7 motor , leaving him behind !!