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Frame/Suspension/Brake... Talk & Q&A All things... Frame/Suspension/Brake

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  #11  
Old 10-28-2017, 09:15 PM
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MercuryMac MercuryMac is offline
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Neto, You are right about having a split steering arm in the middle with two short tie rods running from it will make the inside wheel turn sharper than the outside one, and you want that, but with one long tie rod, the two steering arms are bent inwards not just to miss the tires but to steer the inner wheel sharper than the outer one, too.
I think you're Imagineering something complicated when a simple draglink that's level, [and elliptical springs that are level] will give you no noticeable bump steer. The complicated way has a way more pivots and joints and each one of them has a potential binding point or loose joint possibility, maybe causing poorer steering than simple drag-link steering.
Bump steer is a Coffee-Shop builders lament, not something a thinking builder goes crazy over.
Think it out, read about drag-links and start building it. It'll all work out.
Good Luck.
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  #12  
Old 10-29-2017, 06:03 AM
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smallfoot smallfoot is offline
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I agree with Mac on simplicity. The more joints you have, the more trouble spots you build into a system where you want as few problems as possible.
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  #13  
Old 10-29-2017, 01:23 PM
Neto Neto is offline
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Quote:
Originally Posted by Dr Crankenstein View Post
Neto: How can tie-rods become shorter in length???

I can't imagine how any combination of links and pivots could increase or decrease Ackermann. The attachment points are fixed. The steering arms and/or spindles are fixed. You could increase steering ratio with a bell-crank or two, but the Ackermann geometry will remain fixed.

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Quote:
Originally Posted by MercuryMac View Post
Neto, You are right about having a split steering arm in the middle with two short tie rods running from it will make the inside wheel turn sharper than the outside one, and you want that, but with one long tie rod, the two steering arms are bent inwards not just to miss the tires but to steer the inner wheel sharper than the outer one, too.
I think you're Imagineering something complicated when a simple draglink that's level, [and elliptical springs that are level] will give you no noticeable bump steer. The complicated way has a way more pivots and joints and each one of them has a potential binding point or loose joint possibility, maybe causing poorer steering than simple drag-link steering.
Bump steer is a Coffee-Shop builders lament, not something a thinking builder goes crazy over.
Think it out, read about drag-links and start building it. It'll all work out.
Good Luck.
Thank you both for your input on this. I wasnít much thinking about the greatly increased number of joints to add slack into the steering design.

What I meant about the Ackerman ratio being different for a one-piece tie-rod as opposed to a two-piece tie-rod design with the bell crank in the center, is that when in a tight turn, the over-all distance from the steering arm ball joint center to the opposite one is a bit shorter with the two-piece design than it is with the one-piece tie-rod. In that sense, the Ackerman ratio is a bit different, that is, the degree of difference between the two wheels is a bit more with the two-piece tie-rod design, because as the bell crank turns, it lessens the distance between the tie rod centers left to right. (Because of the angle of the two holes. I donít think I can explain myself any better than this, and Iím not good at drawing.)
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  #14  
Old 10-29-2017, 07:46 PM
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Dr Crankenstein Dr Crankenstein is offline
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I think I understand your theory, Neto, but I doubt any significant gain.

A wise man once said, "Of all the sins you can commit when building a rod, bad Ackermann is the least serious." donsrods

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  #15  
Old 10-29-2017, 08:41 PM
Neto Neto is offline
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Quote:
Originally Posted by Dr Crankenstein View Post
I think I understand your theory, Neto, but I doubt any significant gain.

A wise man once said, "Of all the sins you can commit when building a rod, bad Ackermann is the least serious." donsrods

.
Yeah, I doubt if it makes much difference at all (maybe few degrees at most?)- just doing a lot of thinking because I can't afford to do any 'doing' right now.
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