Some quick questions

[speedy king]

Just wondering if people can help me out on a few things,

I've been looking on the net for a Battery holder for the Rotax, can't find them on zoomkarts, in practice i just attached it at the front near the steering column with lots of tie raps done up tightly and it didn't move at all, i'm pretty sure though that wouldn't pass scrutineering though however i've seen people with the battery placed there before and idealy i'd like it to stay there as i want more weight over the front to increase front end grip.

One other thing. i need to add 12kg's to meet the minimum weight, which made it a great Christmas not havignt o worry too much about putting weight on but i've heard some people fill cans and bottles up with lead and sand. Is sand allowed or does it have to be lead, in Juniors i was always overweight so never had to worry about it.

[Alex Hodgkinson]

For the weight, always use lead. It's much more dense than sand at 11,340kg/m3, against sand's 1602 kg/m3, so you'll have to use 7 times as much sand than you would if you were using lead! And 12kg's of sand will be a bloody lot.

Just get some lead from anywhere, off your roof if you must, and melt it down with a blowtorch and pour it into an old baking tray to give it some shape. Then cut it up however you need to.

As for the battery holder? Not a clue, sorry, asked DK? My dad always makes our own brackets and holders.

[Nigel Wilson]

Lead weights should weigh no more than 5kg each and be fastened with 2 bolts. Don't put it at the front (or the battery) the kart will not turn in as well. Put it around the base of the seat and more on the left to counter the weight of the engine. Think of a mid engined car, it has better agility than a front or rear engined, because the majority of the weight is in the middle. I don't know all the theory but if you do a search on UK Karting forums cleverer people than me will explain it better.

[toot toot]

Always put the lead on the seat aslow down as possible, this gives better handling and stability than putting it anywhere else. Place the first peice on the under side of the seat between the legs. The second peice on the brake side of the seat. Thhe third peice on the engine side. The fourth peice on the back brake side (remembering to keep it low). And if you need more places to lead after that eat more!

[Revracing]

I always put the battery at the front end, mainly because I had no where else to put it, never experienced any downside to it.

There are many theories regarding weight distribution, the bottom line is put it where it is most effective, if it helps at the front, put it there. raising or lowering the lead is also useful in certain circumstances. Remember no two drivers are the same nor are any two drivers setups. if it works for you then don't worry about where it goes.

One thing to bear in mind though is this, raising the lead will lift the COG and make the tyres work harder, and vise versa (the same goes for the drivers position).

[speedy king]

Thanks for the help

Interesting about how it needs to be placed low in terms of the centre of gravity, had never thought about that. Guess most places such as Dartford karting sell these? Any ideas of prices?

[Alex Hodgkinson]

Defiantly something that you need to consider, especially being in the 6ft club.

It can be worth it drilling another set of holes higher up on the seat so that you can move the lead and COG higher up for that bit more bite from your outsides. That's something I implement when conditions call for it.


What Nigel said about the position of weight longitudinally on the kart is all to do with moment & momentum vs.tyre grip.
Front tyres when turning in always have to overcome the forward momentum of the mass of the kart, ie. the kart always wants to go straight. If they don't overcome it you end up with your tyres pointing at the corner but you're going straight on.
This is also because tyres can only grip in one direction at a time - forwards or sideways, any diagonal grip between is minimal.
A certain amount of weight at the front will aid turn in because it'll push the tyres down, but once you get above that level you'll get a big drop-off of bite for the reason I just stated.

If the weight's all at the back, you can get the opposite thing happening on turn in. You'll get MASSIVE amounts of back end grip, but the front end is floaty, light and won't grip. You won't loose back end grip on turn in because they aren't doing any turning in. However once you get the fronts to bight, the mass you've got becomes a lateral-enemy. The mass just wants to carry straight on. Hence the back-end will move forever closer to the outside of a corner.

You can see why a centrally focused weight distribution is the best option, because it'll push down on both front and rear about equally. Playing a bit with for example 52%-48% weight distributions is the key.

It might sound daft, but when talking about weight distribution in a kart's setup it's forgotten that mass doesn't just push down.



Edit: Yeah DK will sell them, or just get some and melt it down as I said.

[marcus]

here in Australia I know that you are only allowed to bolt lead onto your seat.

it will not pass scrutineering if it is anywhere else.

I had about 4 holes in my seat and thankfully only needed 5kg to get up to weight and tried in all 4 places (2 high 2 low) to see what worked best.

I honestly dont know what the best place was best but I did feel more comfortable with it down low

[ukkartace]

its common knowledge that you place lead, low in the dry and high in the wet. another important idea is making sure theres even distrubution of it. i.e corner wieghting your kart - believe me it makes a huge difference to handling and tyre wear.

have you tried gettign a battery holde of strawberry speedy king as i'm pretty sure the same battery is used for rotax as it is in the Tonykart ROK cladss in which case tonykart must make some brackets. the simple bolt it through the floor tray or chassis bracket at front of your kart.

[speedy king]

Thanks, may ask at strawberry, it's a Trulli that i have anyway so if its used for Tony karts then it'll be fine. Will still try it on the back of the seat too, experiment around a bit

[BillyT]

have you got a picture of your new Trulli speedy?

[speedy king]

I'm attempting making a battery holder to go on the seat. If i use bent metal/heavy duty plastic and form a box shape which the battery can sit in and then be tied in with tie raps and the box drilled to the seat would the scrutineers allow it? Obviously the bateery would be held in bloomin tight

[shiny side up!]

Be careful with the design of your metal battery tray/holder, you must make sure the holder does not touch the battery terminals or any uninsulated bits of wire. Also, if the battery has an acid drain/overflow, you will want to be careful to clean it often so it doesn't corrode the holder and drop your battery on the track!