Adding weight (where?) for class racing

Pete Ryan

there are a lot of people that like to add all of the weight to the seat to make it as if there is a larger driver. normally you would try to keep the wight low. depending on the brand of chassis you have you would want to run certain percentages in the front rear and sides. try calling or emailing your chassis company and see what they recomend percentage wise. then you will find if you need to add weight to the front or rails

Roger Miller

Where you add the weight largely depends on how your kart scales out. Front/Rear percentage and then 50/50 side to side. YOu can help the front to rear split by where the weight goes. Look at juniors, they often have weight out on the front of the kart.

People add weight to the seat to simulate a larger, heavier driver. OK, then you have to move the seat forward or backward to adjust the front/rear balance.

If the kart is too tight in the back, you might want to raise the weight up higher on the seat, help the kart to work in the corners.

Answer really is: It depends, and being able to add the weight where you want it is an advantage.

Paul Carey

To race in our chosen 100cc clutch kart class, my buddie and I will need to add from 40 (me) to 90 (him) pounds of weight. Our thought was to add it all as low as possible and as close to the center of the frame as possible, making sure the kart scales out well balanced when the dust settles. I've seen weight on frame rails, seat bottoms and seat sides higher up. Where is best and why?

Thanks,

Paul Carey
pcarey@dpfnapa.com

John Zimmer · Joined: 04 Dec 2001 Posts: 4 Location: MN

I run a 125 shifter kart, but I only weigh 125 lbs. This poses a big problem every year because we usually have to add about 75lbs of lead somewhere. A good method to try is putting the kart on scales with you in it and then setting the weight in the seat and on the frame in various places. Then you can watch the percentages change as you move the weight around. Get the percentages you want and mount the weight in those locations. We usually try to keep it low and a lot usually ends up on the seat. I believe Russell karting sells weight tanks that look really nice and hold about 15 lbs. It bolts right on to frame rail.

John

Christopher Livengood · Joined: 28 Nov 2001 Posts: 119

We ussualy get a new seat and do like john said. We clamp a board to the bottoms of the frame then i sit in the seat. We move it to the desired peosition. This should be close to perfect on the scales but doesnt have to be exact. We like to bolt steel plates under the front of the seat and just behind the gas tank. Like on the steering uprights. Dont put them to low, that way you stiffen up the bar down below. We also casted led cones around 2 inches high. We used these to prop up the front of the seat. It depends on your virticle CG and the stiffness of the kart weather or not to bolt weight high or low. With me being short we like to keep the seat up straight and a couple lead weights on the top of the seat sides.

chall · Joined: 25 Aug 2001 Posts: 16

I know a lot of people will disagree with me but I think adding weight to the seat is not a good thing to do. I see the seat as a safety device and drilling holes for bolts will weaken it. The weights on the outside will concentrate an impact at the weakened point. The seat might not fail but will flex more, and what does it flex into? Your body. I find bruises and fractures to be one of the least appealing aspects of karting. Chris

jhixon · Joined: 10 Nov 2001 Posts: 18

I lean toward Chris on this one. The seat moves and flexes a lot compared to other frame members. I think this would make the weight distribution more dynamic on the track. It might be better to concentrate on the frame rails and maintain the structural integrity of the seat.

Paul Carey

Interesting point, Chris. So where do you mount them?

Christopher Livengood · Joined: 28 Nov 2001 Posts: 119

If you are asking where to mount the weights under the front of the seat. I dont mean mount them to the seat. We cut these steel plates to a rectangle shape. Now, think as if you were looking at a side veiw of your kart. The steering up-rights go forward on a more horizonatal angle than virtical. This is where to bolt them in. We then remove the gas tank. Place a plate on the top and the bottom of the the steering up-rights where I described. You can mount as many plates on the top of the up-rights as are needed. Don't mount them where the up-rights bend up this may cause them to break. Next, we drill a hole down the middle of them. The two plates we want to be the bottom plate(under the up-rights) and the bottom(plate thats touching the top side of the up-rights tubes) of the stack on top. We then weld shanks of bolts on the sides to keep them from rotating.
As for mounting weights to the seat this was also a concern to me. We use very big low profile washers to spread the load but not intrude into my ribs. We have one quarter padded the seats also.

chall · Joined: 25 Aug 2001 Posts: 16

Paul, I try to mount weight to the frame rails or seat struts and steering supports( if I think they are strong enough to hold it). I try to use seat height to adjust
VCG. That can be a very corse adjustment so being able to move weight on the struts becomes very important. I will mount weight to a seat at the track, only as a last resort, and then with great trepidation. When I get home I will go to the Bridgeport and make a mount to get the weight off the seat.

IMHO, mounting weight on the seat increases risk of injury SLIGHTLY, a risk I try not to take. Others who are faster don't seem to mind or haven't realized the risk increase. I don't judge them, we are the masters of our own destines.

Chris

Pete Ryan

quote:
Originally posted by John Zimmer75:
I run a 125 shifter kart, but I only weigh 125 lbs. This poses a big problem every year because we usually have to add about 75lbs of lead somewhere. A good method to try is putting the kart on scales with you in it and then setting the weight in the seat and on the frame in various places. Then you can watch the percentages change as you move the weight around. Get the percentages you want and mount the weight in those locations. We usually try to keep it low and a lot usually ends up on the seat. I believe Russell karting sells weight tanks that look really nice and hold about 15 lbs. It bolts right on to frame rail.

John

i will be running 125 shifter and i only weigh 98 lbs so if you think your kart is heavy mine will be heavier

Martin Secrest

Don't forget some of the other things you can do to add to the overall weight of the kart, such as:

1) Add a full rear bumper if you don't already have one. Make it as stout and heavy as possible.

2) Add an extra fuel tank and fill it with water.

3) Use a heavier gauge floorpan.

4) Use heavier wheels.

5) Add some instruments, such as a speedo, which (if it's like mine) can add about 3 pounds.

6) Paint your bodywork.

Also, when I add lead, the first place I like to put it is underneath the seat, on the floorpan, in sheets that are roughly a foot square. Double layers or more, making sure you bolt them to the floorpan in an approved manner.

--
Martin Secrest
WKC PPC Enduro

Patrick Hubbell

quote:
Originally posted by Paul Carey:
To race in our chosen 100cc clutch kart class, my buddie and I will need to add from 40 (me) to 90 (him) pounds of weight. Our thought was to add it all as low as possible and as close to the center of the frame as possible, making sure the kart scales out well balanced when the dust settles. I've seen weight on frame rails, seat bottoms and seat sides higher up. Where is best and why?

Thanks,

Paul Carey
pcarey@dpfnapa.com

90 pounds !!!!! Holy lead bricks, batman!
Choose another class.

Generaly the weight should be mounted to the seat as has been suggested. That much weight though may never fit on the seat. You will need to spread it around. On the seat you should not mount it all low as that will affect the handling. You need some up high to assist with weight transfer and loading of the outside wheels.

90 pounds WOW! Now that's a "lead sled".

Good luck. To minimize the number of weights and the holes you will need to mount all that weight, you may want to make your own ingots. By shot lead and melt it on a propane stove then pour into metal baking pans. Be sure to use ones that have angled sides to help with removing the ingot from the mold/pan. Use 5/16 bolts with fender washers sandwiched between all surfaces and safety wire them(bolts).