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Old 01-15-2020, 06:47 PM
*tonto* *tonto* is offline
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Default Steering help.

Hi everybody, new to the forum. I have recently built a mini atv powered kids powerwheels go kart, and have come to a bit of an issue. Because of the live axle, the seat, and most of the weight in the back, the kart has a crazy amount of understeer. The front track width is 2 inches wider than the rear. I have played around with different mounting locations on the idlers and pitman arm to try and maximize steering throw, but the most i can get is only a few degrees. My front a-arms are welded fixed, so there is no suspension or bump steer at any time. The front has 10 to 15 degrees castor and the same amount of camber. I am trying to build this with scrap stuff i have lying around the house, and currently i am into the entire project for around $100. I would appreciate any feedback on the steering as it is the last part to make this thing really special. I will try and post the pics now. Thank you.
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  #2  
Old 01-15-2020, 08:05 PM
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itsid itsid is offline
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You could try to improve the Ackermann angle ..
it looks to be okay'sih at first glance, but it's hard to tell for sure..

Just get a string to the kingpin center (ideally at the height of the steering linkage)
and tie the other end dead center to your rear axle drawing a straight line.
if the tie rod knuckle is dead center on the string if the wheels point straight ahead,
the angle is as good as it gets.
Otherwise you might want to alter the spindle linkage just a bit more to get closer.

If that fails, then the rest is indeed up to the weight being mostly above the rear axle..
and since it cannot flex with the weight above it,
it'll just push the lightweight front straight ahead no matter what the front wheels are doing.

YOu can still improve the steering a little by getting narrower front wheels.
Or what is likely the best thing, convert to either a differential axle
(peerless 100 is rather easy to find and inexpensive..)
Or just replace one of your rear wheel keyed hubs with a bearing hub.
converting the kart to a one wheel drive.

I prefere the differential approach tbh,
but you'll need two rear brakes in order to positively stop the vehicle from moving.

'sid
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Old 01-16-2020, 06:22 AM
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If possible you can rebuild the steering to the front and make the spindle bolt longer so you can add spacing. then if it doesnt give enough angle try to make the spindle arm (?) A little more inline with the wheel. My ken bar has a 90 angle between the arm and spindle bolt, and it has a ton of drift angle. Ill see if i can make a diagram. Cool build btw
heres a good example khana karts! they have Moreangle then my ken bar. im giving example for more angle but not saying it has to have drift angle but it would be cool lol. Excuse the bad writing and drawing lol
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Old 01-16-2020, 09:40 AM
*tonto* *tonto* is offline
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Thank you both for the replies. I think i going to try and change the ackerman a little, and possibly try and space out the front tires on new homemade spindles. I will try that and report back. Cheers
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Old 01-16-2020, 09:40 AM
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First off, let me say that is a cool build. I like it a lot.
I see some problems with the steering geometry though. It looks to me like you need to extend the steering column to the point that when steering is straight that the tie rods form a straight line from side to side. It also looks like your Ackerman angle may be overshot, the way Sid describes to check it is right on, but the Ackerman may work as is. If it were mine I’d get the tie rods straight and see how it behaves.
A quick and dirty way to check would be to flip the tie rods to the other side of the plate on the steering shaft. I’d bet that you’ll see a major improvement just by doing that.
I specialized in steering and suspension as an auto mechanic for 22 years and had a reputation as the best in the area, I’ve sat for hours in classes on steering geometry, along with a whole lot if real world experience, so at least humor me on this one.
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Old 01-16-2020, 10:50 PM
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^^^^^^Try what he says first...I did some time on the alignment rack years ago when I worked in the shop...replacing worn out parts is one thing...I remember having to do school buses for the local tech school...I had to ask the 'old guys' for help...cause some things just ain't in the books...anyway...long story short...never overlook good advice if someone offers it freely cause sometimes it's hard to ask for it otherwise...
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Old 01-20-2020, 02:46 PM
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Well, after hours of looking at it and scratching my head i think i got somewhere. I took a few of the different ideas i got from here and tweaked them just a bit. First off i took the hubs off the rims and flipped them so the dish was bigger on the outside. This made the pivot point further out. Second i changed the mounting points on the pitman arm to give it more swing and greater angle. Last i changed the idler arms to correct ackerman to almost perfect. I just tacked everything together to see if it would work, and i think i increased my steering angle by at least double. I will have to take it out later to see how it handles while under power. I appreciate all of the feedback, and hope to modify this thing further in the future. Thanks.
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