Evolution of a Suspension Kart

[ainavatar]

hey all, i want to use this suspension on my go kart but i first need to know what thickness i should use for the flat stock?

 

[frederic]

Since I am planning to productize this, I cannot reveal all of the secret sauce. However, Leaf Spring steel is incredibly common, and robust. It is a bit heavy compared to the high temper steel, but a good starting point. Look for 1/4 to 3/8" thickness for a single beam suspension.

You don't need to reveal the sauce because those of us with fancy HP calculators can do the math necessary to calculate the appropriate width, thickness, alloy necessary for a given load both sprung and unsprung.

Teasing aside, let me help you out a bit.

First of all, it can be welded. Typically it's 1095 or more likely 5160. To weld either, you'd need an arc welder and specialized rods such as the "Zena No-Gas" series. You will have to heat treat by heating up to a non-magnetic state and allowing to cool to black two or three times, then you harden it by heating again to a non-magnetic state and quenching in oil. 5160 typically requires three additional heat cycles/oil quenching to be considered properly tempered again, 1095 requires one or two, I forget.

I realize it's unlikely that you'd want to go through all this but I'm sharing this information because it's information, and debunks the common statement of "spring steel cannot be welded". Absolutely it can, if done right. Would the average Joe want to? Absolutely not ;-) This applies regardless of shape - flat, arched, rod.

Drilling spring steel isn't a hassle with the right tools. First of all, toss out all your HSS bits whether coated or not and acquire yourself appropriately sized micrograin carbide bits.

They're worth the money because they eat right through both alloys very well if kept in the 800-1000 range and wet. You can use official cutting fluid if you're wealthy or automotive radiator coolant if you're not. A heavy, rigid machine will help here (i.e. not a Sears benchtop drill press). An import mill/drill unit in the $1000 range is about right. Since you're thinking about production, a new or used milling machine would be a worthwhile investment for more than boring holes.

Better/quicker/safer than boring pointy carbide through spring steel is a hydraulic punch machine, and they're very easy to set up for repeated punches for production work. If you are a frugal bloke you can buy a used machine and replace the worn out dies. A hydraulic punching machine is nothing more than a heavy arm actuated by a large hydraulic cylinder, supported by an even bigger pivot. Apply hydraulic pressure via a button or foot valve, arm moves down, pushing die through material/work into reverse die. With clever die making you can punch multiple holes at once if you have that need. Much easier and consistent than flipping a thick flat over to punch another hole side by side of the first hole.

Hopefully those three tidbits of information help you out in some way. Good luck in your endeavor. I always like to see people succeed with great ideas. My only concern would be spring twist, a common problem with leave-spring vehicles. Anyone who has overloaded a pickup truck and tried to take a corner and *not* flip know what I'm describing.

 

[Doc Sprocket]

breakage is weakness leaving the design.

Excellent attitude! I like it! Also- Scars are tattoos with better stories!

On a more related note, this spring steel biz looks a bit much for your average backyard wrench- but very interesting all the same. I have wondered about the use of light utility trailer (or similar) leaf springs applied to a kart. Not for a moment will I detract from your wonderful design, but outta my league for difficulty and cost. Keep up the good work, and keep us well informed! Cheers- Chris

 

[Russell ATV]

Ok, after a slight vacation from karting over the long hot Texas summer, I am playing around with the stuff again. The single Engine Kart with the cider block pictures was upgraded with a Chinease TAV2, and has been a work horse. The twin engine kart managed to get the cops called on me. I guess some people do not like you doing 55MPH in the neighberhood. A buddy and I recorded a lot of jumping a week or two ago, and he owes me a disk. I will see about some YouTube stuff.

Now, I need an idea for something new using the spring steel design. I want to do somehing really light and small. I have a good little 2 stroke, 4HP engine begging to be used.

Russ
Russell ATV

Russ