single or double a-arms
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thechief86
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i think double arms will be stronger and handle better, but be heavier. also you could possibly use the space between them to locate an axle for 4 wheel drive later, like on a toyota. more thought would have to go into a single a-arm set up to keep it strong, but i'm sure you could make it more than adequate for a kart.
Dual a arms gives you more travel, you can adjust them for caster camber, but they take more planing in designing them, and much more party. They are also more costly.
Single a arms don't give you much travel, simpler, cheaper to build and also lighter.
Single a arms don't give you much travel, simpler, cheaper to build and also lighter.
weight is not really a problem because i'm using a 337 cc 2-stroke for power. i think i could make a single arm strong enough, so i dont think that would be an issue. long travel is not really necessary, but it would be cool, so that is what i am striving for. why exactly would single arms limit the amount of travel? if they actually do, then i guess i'll go with double arms. i just dont want to complicate things if there is no benefit (other than the adjustability mentioned earlier).
modelengineer
Lord of the noise
They don't. Single arms can have just as much travel as double, but you will get massive negative camber at full bump.
The main disadvantage to single arms is the camber change over suspension travel.
The main disadvantage to single arms is the camber change over suspension travel.
Doc Sprocket
*********
+1 Modelengineer, exactly! A double A-arm setup will allow the spindle to remain at the same camber angle throughout the full arc of the suspension, while a single a-arm keeps the spindle fixed ralative to the arm, so as the suspension arcs, the spindle moves through the arc changing the camber angle dramatically as it goes up and down.
motor_head
expert garbage picker
singe a arms are generally fine for offroad but onroad it better to have the tire strait up and down
for a simple off road play buggy single a arms are just fine, just look at the edge buggies sidewinder and the older Piranha and they were the machine several years ago.
Just because you have dual a arms doesn't mean you can get lots of travel from them, you also need expensive shocks which will allow you to get it.
Just because you have dual a arms doesn't mean you can get lots of travel from them, you also need expensive shocks which will allow you to get it.
http://cgi.ebay.com/ebaymotors/HOND...442919QQptZMotorsQ5fATVQ5fPartsQ5fAccessories
they are, for this application, trailing arms and absorb bumps really well. they have a forward mounted pivot.
they are, for this application, trailing arms and absorb bumps really well. they have a forward mounted pivot.
motor_head
expert garbage picker
those would work good thats what my '86 fourtrax has and they work (be better is the shocks weren't shot
The issue with those is now your kpi changes throughout travel. The later Ody FL350 ran a dual trailing arm set up to compensate. It just depends where you want to have greater performance, or where you want to save time/weight/money. All 4 setups have their pros and cons.
chetcpo
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I'm late to the game but I agree with those that said go with single arms. For a simple yard kart they will be fine. Technically the single arm setups are referred to as a swingarm type suspension. Like others mentioned, it provides negative camber gain in bump, which doesn't hurt anything. Negative camber gain is actually desired in cases where the chassis is rolling in corners, and this keeps the tire more vertical to the ground. I'm not sure how useful this is on karts but it couldn't hurt. The knock against swingarm suspensions is that with enough chassis roll it can introduce jacking forces which will cause sudden and abrupt changes in handling. Think "Corvair." I can't see this being a big issue on a kart as I've never seen one exhibit "body roll."
A double a arm suspension can be made to do lots of different things depending on the design. Parallel equal length arms will keep your tires planted vertically with zero camber gain or loss in bump and droop. You can use unequal length non parallel arms and get camber gain in bump similar to the swingarm style's single arm setup. (upper arm in most cases is made to be about 2/3 of the length of the lower) Lots of factors need to be considered when choosing your double a arm configuration. It can get pretty complicated.
In all cases the amount of travel is dictated primarily by the shock, how it's mounted and the motion ratio. Most kart shocks I've seen only have about 2" of stroke. You can change the motion ratio by altering their mounting location on the lower a arm. For example, getting 4" of wheel movement while using one of these shocks with a 2" stroke would require mounting them halfway between the wheel and the inboard a arm pivot. Obviously the further inboard you move them the less effective the spring becomes. Also the mounting angle needs to be considered as it too alters the effectiveness of the spring and motion ratio. You can get really fancy and use pushrods and bellcranks to acheive nearly any desired motion ratio.
Also the length of the lower A arm, be it double or single will dictate how much of that suspension travel is useful. The longer the arms the less erratic the wheel movement.
Sorry to ramble on.
I just meant to say, use long single arms and give due consideration to your shock mounting location and angle.
Good luck!
A double a arm suspension can be made to do lots of different things depending on the design. Parallel equal length arms will keep your tires planted vertically with zero camber gain or loss in bump and droop. You can use unequal length non parallel arms and get camber gain in bump similar to the swingarm style's single arm setup. (upper arm in most cases is made to be about 2/3 of the length of the lower) Lots of factors need to be considered when choosing your double a arm configuration. It can get pretty complicated.
In all cases the amount of travel is dictated primarily by the shock, how it's mounted and the motion ratio. Most kart shocks I've seen only have about 2" of stroke. You can change the motion ratio by altering their mounting location on the lower a arm. For example, getting 4" of wheel movement while using one of these shocks with a 2" stroke would require mounting them halfway between the wheel and the inboard a arm pivot. Obviously the further inboard you move them the less effective the spring becomes. Also the mounting angle needs to be considered as it too alters the effectiveness of the spring and motion ratio. You can get really fancy and use pushrods and bellcranks to acheive nearly any desired motion ratio.
Also the length of the lower A arm, be it double or single will dictate how much of that suspension travel is useful. The longer the arms the less erratic the wheel movement.
Sorry to ramble on.
I just meant to say, use long single arms and give due consideration to your shock mounting location and angle.Good luck!
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modelengineer
Lord of the noise
Negative camber gain, but yeah, I'd go with single arms too (well... I do have them on my kart and they work really well)
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