Opposing Spring Steering Aids

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Teeeman
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Opposing Spring Steering Aids

Post by Teeeman » Wed May 30, 2007 9:25 pm

We tried the dual spring thing that almost everyone around here "swears by"...

I had thought about it 2 years ago and said it was useless... but 3-4 folks around here insisted it helped...

we tried it tonight...

basic principles win again...

it didn't help.

We took 'em off.

The adjustable steering stop works nice though :)

-Terry


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sporty
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Re: Opposing Spring Steering Aids

Post by sporty » Thu May 31, 2007 3:20 am

Must not be something I mentioned.


You will have mention a little more. I am not sure I know what the duel spring steering is.

Sporty



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Re: Opposing Spring Steering Aids

Post by Teeeman » Thu May 31, 2007 3:18 pm

... sorry...

it is using 2 heavy opposing springs to attempt to add high speed stability to the sensitive steering ...

think the goal is to be able to leave the steering effective for turning but to get rid of the twitchiness...

but for racing what you really want is just near-zero steering.

I have looked also at adding a linkage steer to our new lightweight car but that is going the wrong direction… heavier.

It worked but the kids didn’t like it (we modified it with spare parts).

It runs so nice the way it is… but it takes a skilled and seasoned rider if you get up to any speeds in excess of 10MPH or so.

-Terry


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sporty
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Re: Opposing Spring Steering Aids

Post by sporty » Thu May 31, 2007 6:02 pm

no worries,

Thanks for explaining it to me.


Hmm, It is a interesting idea. Was the spirngs just to stiff ? or just the opposite ?

I always wondered if you used like the hydraulics for car hood and trunks. But then thats designed for alot more weight.

But a smaller one, that was designed for much smaller load use. That would be interesting to see how well or not well that it worked.

Sporty



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Re: Opposing Spring Steering Aids

Post by Teeeman » Fri Jun 01, 2007 8:56 pm

The problem is the springs are at their weakest when you are going straight and don't help any really... since they are canceling each other.
It would take a heck of a pre-load on a pretty strong spring on each side to make enough difference to matter.

What would work better is a very stiff damper.

Dampers allow motion but they resist the speed of the motion... but once they move to a new position they do not try to push or pull...

for vehicles with suspension there is always a pairing of springs which provide force and dampers (shock absorbers) which resist fast change of position...

i.e. when you load a pickup slowly, the dampers do nothing but the springs are always pushing and push harder the more you move them...

the shocks would do nothing during loading.


2nd i.e. going down the road you hit a relatively small 1inch deep crater in the road... it is a very fast event... the dampers will make it feel sharp by not allowing a FAST change in position even if the 1inch deflection is not much to the springs...

the key is they work together and there is a damping coefficient that can be calculated easily... a car that is engineered at the factory will have a chosen damping coefficient usually around 1.0 I think...

when folks change springs in a car, if they don't change shocks to match the new spring rates they usually get a less than optimized ride though it is probably not "off" enough to make much difference...

etc.

I'm not an expert, some of this may be a little off kilter but I think the summary is this:

Our CMBs would benefit from some high damping rate shocks on the steering or just a really tight bushing (I would think the bushing is the right way to go).

In our case and in that of most CMBs... the ultimate easy solution in addition to steering stops is just tighten the pee-pee outta the front axle attach :)


-T


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Re: Opposing Spring Steering Aids

Post by PWD » Fri Jun 01, 2007 10:20 pm

Never built a soap box derby car. But how hard is it to get the alignment correct so the car goes straight? As hard as getting a PWD car to go straight :) Do you have to have steering? How much does the scout have to steer?



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sporty
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Re: Opposing Spring Steering Aids

Post by sporty » Sat Jun 02, 2007 4:40 am

Cubmobile is not hard to build.


Set up is not hard either, I think it's easier to do a Cubmobile than a PWD car.

PWD are much smaller and everything has to be perfect for a fast one.

With a Cubmobile you are working with a larger scale and easier to deal with.

A soap box derby car, if you want to win or do well, its hard. The alignement tools alone can run you easily $500.00.

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Re: Opposing Spring Steering Aids

Post by Smell of pine » Mon Jun 04, 2007 1:56 pm

We've always incorporated a trailing type steering setup that returns to center very well. We've never had any issues. Drives very straight.



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Re: Opposing Spring Steering Aids

Post by Teeeman » Mon Jun 04, 2007 6:44 pm

Our axle plane is behind the pivot plane if that is what you mean?

Pics?


Even with this, our car is twitchy at speed...

but our ramp is huge compared to others I've seen...

and by "at speed" I mean a full speed run from me than a hard push... gets well over 10MPH...

the new car is twitchy once it gets up in the faster speed range even for my son and he is very experienced with driving 4 wheeled things of one flavor or another (had a pedal car at age 3).

He has Green Machine (the metal Huffy version, not the plastic) that is hard as heck to ride... he makes it look easy!
Even with all that going for him the foot-steer on axle car is twitchy.

Now it is easy to drive at "typical" CMB speeds.


-Terry


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sporty
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Re: Opposing Spring Steering Aids

Post by sporty » Mon Jun 04, 2007 7:05 pm

I find some of the issues, come right down to the soft pine wood.

Seems no matter what, after a few runs or even just one. The center bolt loosens up. From the Compression of the wood.

We solved that issue on my sons car last year. It held up good for this year also.

No re-tightening was needed since I first used the new method.

It does not turn much, pretty stiff and 1/8th spacing on each side.

Unless the ramp is steep and the rider will be at a advantage due to curb / angle of the road. no read to anlge off the ramp and then straiten up. Like in Some soap Box Derby races.

Just a strait run with minor adjustments.


Sporty



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Re: Opposing Spring Steering Aids

Post by Smell of pine » Tue Jun 05, 2007 2:01 pm

Teeeman, I don'
tt have any current pictures of the steering setup. The boys are playing with the car, so I hate to tear it apart for pictures. Anyway, our crossmember is on top of the frame. The bolt which was welded to a plate, is set at a slight angle. The plate was bolted to the crossmember. The steering bolt goes through tw bearings mounted in the frame, and secured with a nut on the bottom. So our steering isn't exactly on a flat plane. We If turned enough, the crossmember would scrape into the frame. We do use steering stops though. Works very well.



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