"It's a "Porch-uh"" (ikazuchi)
01/03/2014 at 16:09 • Filed to: Think about the children!
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"It's a "Porch-uh"" (ikazuchi)
01/03/2014 at 16:09 • Filed to: Think about the children! | 0
| 14 |
So now that my oldest kid is now all of three full years old, I want to build him a go-cart some time this year like my father did for me (when I was a wee lad, not this year). Mine was pretty much a piece of plywood with a old lawnmower engine on the back. I want to build something that will last two kids until they are in their teens.
My plan is to build a platform with inboard/pushrod suspension, a swapable engine cradle (for upgrades - 50cc first, 1200cc later), and a full cage (safety third!). My main stumbling point right now is how to design the suspension. I'm researching on the internet, but can't seem to find anything that helps me calculate what spring rates I'll need, or if I have existing springs (like if I used motorcycle rear shocks) how I could design around them.
Does anybody know a good internet resource or even a good book on the subject?
CKeffer
> It's a "Porch-uh"
01/03/2014 at 16:13 |
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Bah, go race kart style, with chassis flex as the suspension :D
http://www.ebay.com/itm/Race-Ready…
http://www.ebay.com/itm/2012-Top-K…
The pics in these should give you an idea of what I'm taking about,
Edit:
Here's a better top down shot of just the chassis for a junior racing kart.
Joe_Limon
> It's a "Porch-uh"
01/03/2014 at 16:13 |
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Try finding/pirating a copy of milliken's race car vehicle dynamics?
As far as go-cart's go, a little chassis/tyre flex is really all they need. Anything else is just added weight.
Brian Silvestro
> It's a "Porch-uh"
01/03/2014 at 16:13 |
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The ones in the picture will do just fine. All you need is an Aventador, and you'll have all the parts you need.
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It's a "Porch-uh"
> CKeffer
01/03/2014 at 16:16 |
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I want it to have enough travel for some minor off-roading. I'm thinking the chassis will be at least 8" off the ground.
CalzoneGolem
> It's a "Porch-uh"
01/03/2014 at 16:19 |
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The beauty of the plywood was that it was the suspension as well.
Jeff-God-of-Biscuits
> It's a "Porch-uh"
01/03/2014 at 16:20 |
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Try Craigs for broken down carts. Fix them up instead. That's what I will most likely try with my son. That way he can learn about how to fix stuff as well.
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Joe_Limon
> It's a "Porch-uh"
01/03/2014 at 16:21 |
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Get a couple sets of springs then, hard ones for pavement, and soft cushy ones for less ideal situations.
HammerheadFistpunch
> It's a "Porch-uh"
01/03/2014 at 16:21 |
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It's a "Porch-uh"
> HammerheadFistpunch
01/03/2014 at 16:23 |
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Thanks!
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CKeffer
> It's a "Porch-uh"
01/03/2014 at 16:30 |
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If you are dead set on that type of thing, then I would be looking at the suspension setups from ATV's to be perfectly honest. Yes an inboard pushrod suspension would be cool, but it will also likely be more complicated and prone to failure vs a more conventional setup. It would also mean that you could likely use the suspension members and springs/shocks from the ATV. A lot can be done with a double whishbone front suspension and a swing arm rear. Other than that, I can't really help you, but maybe this site could give you some ideas *shrug*
http://formula-cross.myshopify.com/products/450fc
davedave1111
> It's a "Porch-uh"
01/03/2014 at 16:34 |
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As far as I know you guys in the US give spring rates in pounds (per inch), which is the number of pounds of force needed to compress the spring one inch.
Other than that, it's just simple geometry once you know the rate of the springs, the weight you're dealing with, and the desired suspension travel.
It's all rather more complicated once you start trying to design proper suspension systems, but for a kart you should be OK as long as the travel's fairly short because the geometry won't change much.
RamblinRover Luxury-Yacht
> davedave1111
01/03/2014 at 16:40 |
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All very true. "Proper" suspension systems aside, I have a kart setup I want to put into effect with some kart parts my family has - a transverse leaf with a rubber bush, and two simple control arms. Grossly inadequate for anything but a kart, but allows me to leave the whole front unsprung and isolate the drive.
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RamblinRover Luxury-Yacht
> It's a "Porch-uh"
01/03/2014 at 16:53 |
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Possibly a stupid question, but why do you want inboard suspension? Typically a kart isn't heavy enough component by component that unsprung weight is any kind of issue at all. If the whole is too light, you could have wheels bobbing/bouncing too much to maintain traction and control like you'd want. Improved return from a hard strike vs. more skipping on a washboard - there are tradeoffs.
I'm planning on building a kart, but leaving the front unsprung - leaving the rear to make up deflection difference through a transverse leaf. That allows me to have solidly mounted kingpins, easy brake mounting and to build the rear as a "power pod" with the engine and trans - effectively making something between proper suspension and an articulated chassis.
Effectively this, but with the engine and transaxle as additional unsprung weight on the axle beam. This allows typical mounting of the engine and trans as rigid to one another, while isolating their vibration from the body of the kart and suspending them to a degree on flotation tires. With seats toward the back of the kart, suspension is where it matters, and the design allows for the bringing of the frame and cage to a point for strength in lightness. Because this "tail" will be above the drivetrain, the lower control arms allow rotation control as well as controlling lateral movement. The whole rear can be set off to change motors...
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It's a "Porch-uh"
> RamblinRover Luxury-Yacht
01/03/2014 at 16:58 |
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I was thinking that would give me the best option for increased ground clearance, but a slightly simpler setup, like an ATV, might be the easier way to go. I was thinking the rear would be from an ATV anyways, as I don't want to get into the driveline complexities of IRS.
Also, I want it to look super cool! Damn the practical issues!