mac853

Could someone tell me difference the advantage of using shorty in modified tc, please?

And why does not worth 21.5 and 17.5 stock class using shorties?

OVA

iTrader: (86)

it simple .mod dont need high voltage and the shorter help lower CG (reduce traction roll)
for spec always need higher Average voltage in 6 minutes races( mean bigger lipo)

gigaplex

iTrader: (2)

Shorty packs are typically the same height as full length. You'd get lower CoG with a full length thin height pack.

daleburr

But the shorty packs are lighter. So you add weight to get back upto the minimum weight limit, and those weights are mounted much lower than the lipo CG, lowering the overall CG.

gigaplex

iTrader: (2)

You can do the exact same thing with the really low profile full length packs.

Sortafast

I quoted the wrong post by mistake, thus making my original reply kinda silly. My apologies, I’ll see myself out

DirkW

iTrader: (1)

What of it is not true with a low profile shorty? That shorty packs are lighter than stick packs of the same height (which was what he responded to)? That you have to add weight to get the car back to minimum weight? That a flat brass weight mounted directly on the chassis plate (in front and behind the battery) has an even lower CoG than even an LCG / low profile shorty? I don't quite see which of his statements becomes untrue.

The reasons why people use shorties in mod (and stick packs in stock) were already given. Nobody claims you have to do it this way or could not maybe get the same result in a different way. Still doesn't make the answers of why people (even world class pros) do it any less true.

bmwjoon

iTrader: (1)

I'm sure there are some guys that use a short Lipo in stock classes. You could make up for the difference in voltage with a really aggressive charging game. I think it has to be the right kind of track too. A larger battery will almost always have a lower IR.

DirkW

iTrader: (1)

On large outdoor asphalt track you'll usually want a full size stick pack with fairly high capacity (7000+). On indoor carpet it's not as crucial. I have two friends / club mates who, when they started on-road stock class racing (coming from off-road), bought (then) all new X-ray T4 kits but didn't want to buy new batteries and wanted to use the shorties they already had for their buggies, so they bought the Xray shorty-mounts (which in itself costs almost as much as a battery), and started out that way. This lasted until they finally tried a full size battery once after a while - both changed over to full size batteries immediately - again: talking about stock class (17.5T in this case, as there are no 21.5T or higher turn classes for touring cars over here). The punch difference, especially in the last third of the race, is apparently very noticeable. In mod on the other side, with open motors and open timing, power is always there in abundance, sometimes even too much (sometimes people don't even charge their batteries up to the full 4.20V per cell), then CoG and position of the battery's weight is what matters, and some people choose shorties for that. Others use LCG stick packs, while again others use the narrow stick packs... I'd call it personal preference.

WayneKerr

iTrader: (2)

No, you can't. Even at the same pack height the cg difference is substantial.

Ran thru this exact exercise Thurs night on my bench and I removed shocks and springs and used dummy dampers to eliminate the load var caused by stiction, put it on setup wheels to isolate effect of battery change.

Maclan 4600 vs 5500 was over 3mm cgh difference after you use the heavy battery holder to compensate.

gwhiz

iTrader: (1)

Super curious how you make this measurement. Do you have a picture of how its done?

gigaplex

iTrader: (2)

So don't use a pack of the same height. The longer pack allows you to maintain comparable capacity while being thinner.

daleburr

The pack you describe doesn't exist. In mod we're using a shorty around 4000mah and 18.5mm tall. The flattest full length pack is the LRP Hyper LCG at 5200mah and 17.5mm tall.

Okay so the full length pack is 1mm flatter, so it has a lower CG... but it's 60g heavier. So once you've added 60g of brass mounts with the shorty pack, the shorty ends up with a CG around 1mm lower.

WayneKerr

iTrader: (2)

​​​​​​DNot have a photo handy, but basically it's finding the balance on four corners raise the rear axle "x" amount, note the front weight and your wheelbase and then it's math and trig by that point.

I'm sure Google would have it. My work involves motorsports and I've done this everytime my team changes cars I already have an excel sheet built in.

blanks596

iTrader: (20)

I have very little understanding of electronics so pardon my ignorance. Does 17.5 pull more on a battery than mod? if you have a shorty 6000 vs a standard 6000 2cell, wouldn't they produce the same amount of power?