Tapio

We were planning a short endurance race this summer in our club. I know they have 4-5 hour races but we want to keep it manageable at one hour or 1.5. If you havent given this much thought there is actually much to consider. To keep things fair to novice drivers I suggested a cap on totals battery mah capacity of 10,000. For eg, 3x 3300mah packs would bring you just under the limit. This would put emphasis on efficiency . From some quick calcs I figured with unlimited batts it would be benefical to run quite a hot set-up. I timed a battery change at 40 secs in my TC3 which incl. taking the body off.
Does anybody know the rules for Tamiya type mega races? Also any input on this type of event would be welcome.

HPIchuk

with the mAh thing, are you talking about linked battery packs or you can only have 3 3300 packs? because if you link packs, the mAh doesnt change only voltage.

smmetz

it sounds like he's talking about limiting the whole race to 10,000 mah, or 3 3300 packs, so that newbies who dont have hundred of $$$ invested in batteries can race. I think he means one battery pack at a time. I think the setup of most 1/10 scale cars would have to be pretty slow for each 3300 pack to last 20-30 minutes (he wants 3 packs to last 1 - 1.5 hours), but I guess it could be done.

HPIchuk

smmetz- he said that you could do unlimited charging. this means that with 3 packs running 10 mins each and a 15-30 min charger you could last forever as long as you dont overheat. so the cars are goin as fast as they want and running the entire race.

killnine

Uhm, I dont know how your going to get 3 packs to last 1.5 hours man. I mean, I think that I get pretty decent times outta my packs but thats like 7 min.....even if i had 3 packs back to back, that would only be about a half an hour. I think endurance works better on the nitro scene (not to mention, its a good chance these "budget" racers are gonna blow $50 when they overheat and crack their motor). I think you need to think this endeavor through a little more

smmetz

If the plan is to re-use the packs, then it's a bit more realistic, but like Killnine said, it will be hard on the motor, maybe a motor heat sink would almost be a must for running this long? Also, to charge a 3300 pack in only 20 minutes would require like 10+ amps of current, I don't know of any charger that goes over 7 amps. (but I don't claim to know all about all chargers). A 7 amp charger should charge a 3300 pack in around 25-30 minutes. If you allow 10-15 minutes cooling time for the batteries, then that means 40 minutes is required to re-use each battery. This would require 20 minute runtimes with each battery, 15 if you don't give the batteries any time to cool. If the car has a stock motor with the right gearing, it is possible to do. Like Tapio said, the emphasis would not be on speed alone, but getting the best speed with a 15-20 minute runtime for each pack.

Anyway, sorry Tapio, I have no idea what the rules are for Tamiya type mega races.

Tapio

Sorry for the delay( I was waiting for an email notice but didnt get any) what I did mean was changing packs unless of course you decided to hook them up in parallel to give you 9900mah!
Indeed with the recharging is where the challenge begins, as smmetz pointed out . Most people have 5 amp max chargers so a full charge may not be reached before you "gotta go".
We were however brainstorming some crazy ideas for efficiency. How about disconnecting the front drive. Low gearing would almost be a must, especially to keep the motor cool. Hard inserts would be good as would getting rid of any extra drag like a wing. Driving style also makes a huge difference.
You could put a stock armature in a can with adjustable timing and time it close to zero.
I think an hour would be best for the 10ah limit.
Nitro? Killnine have you heard of nitro guys running for five hours?

Tapio

Oh yeah another idea for lowering current draw was to run harder brushes, suppossed to be easier on the comm too.

HPIchuk

nitro guys can do it.

one problem with your theory...when you link batteries, all you do is increase voltage(add up the packs amount) the mAh doesnt change. and ofcourse as we all know, higher voltage means quicker battery drain and hotter motors. so linking batteries is out of the question. my 1500mAh packs run close to 10 minutes if not more. you could have more of these(more than 3) so charging and running for so long would not be a problem.

Tapio

Sorry HPIchuk but there are two ways to connect batteries and or cells, one being in series and the other in parallel. In series the voltage is multiplied and in parallel the capacity is multiplied.
This is common in the LiPo batts to hook them up in both series and parallel where the parallel connection helps discharge at a higher rate.

Tapio

Last time I searched I only found foreign language stuff but this time I found a US race in April!
The link is www.tamiyausa.com/events/enduro/enduro_04.html