Changing front suspension geometry

[WolfOne]

There is a thing that I don't love of my sled ... the front subframe.

I'm trying to think 'out of the box' about this heavy piggy

I think I could built it in one piece carbonfiber together with the engine frames and the tunnel but ...

... to simplify the work and clear this 'all curved' area it could be fine change the geometry like the following draw

The upper draw is + - the stock geometry seen from the front

The lower draw is + - what is in my mind. Same ski stance, same shock lenght and linkage ... shorter upper and lower arms.

A pretty square linkage area is easy to build and easy to make it very strong.

Shorter arms seems to be lighter and stronger than long ones.

I'm trying to figure out, in my mind and on paper, which differences could came out from this mod in the suspension work and in the handling of the sled

 

[rlcofmn]

A longer A arm will make for more constant suspension movement, by shortening your arms the ski's will move in and out more through the travel of your suspension. So for conversation sake without actually figuring out exact with stock from fully extended to where the arms are level your ski's will out say 1" if you shortened them now it will travel out say 3-4" thus your width of your sled is going to vary a lot more with shorter a arms. Longer a arms are better for suspension geometry. For example look at Baja trucks where the arms actually cross to make for a flatter arm with longer travel. This is a Idea I have had brewing in my head to make a long travel sled.

If It was me I would do whatever it takes to make full length A arms, If anything you could incorporate a better front end like the Polaris IQ front end but I personally would not shorten them.

This is by no means expert advise, just thoughts from someone who spends a lot of time thinking about how things work.

 

[Nikolai]

The older AC ZR3 chassis(1m's) had equal length a-arms(or darn close) but travel was short and they were low to the ground. I'm with Rick, I'd make them as long as possible.

 

[bholmlate]

Wolfone you would be limiting the actual travel of the suspension by using short A-arms. You also would be asking every ball-joint in the fron end to work at sharper angles or even bind which usually means pre-mature wear and failure. regardless of the length you choose, (Edit) as mentioned in posts after this one equal length A-arms can cause iusses in handling in the front geometry of a sled as the skies travel up and down and the sled rolls from side to side in corners (edit)

As rlcofmn mentioned the shorter the arms the more drastic the changes to the position of the skies throughout the travel. In off-road racing this condition sometimes leads bump steering. As the wheels travel up and down and if things are not set up right the tires will actually change directions causing the car to become unstable and actaully steer the car in one direction or the other depending on where they are in the travel cycle regardless of any steering input by the driver.

In your case the skies would move in or out depending on where they are in the travel cycle causeing the ski stance to become narrow at top and bottom of the cycle and wide mid cycle.

I think that ground clearance is the biggest hurdle that you have when it comes to making a long travel front end for a sled. if the skid plate hits the ground it doesnt matter if you still have suspension travel in the skies the rider will then absord the rest of the energy.

 

[WolfOne]

You are absolutely right and I feel a little #*$&@ for not having guessed right away.
And with a four equal arms there will be problems in the turns on groomed snow because the angle of camber of the outside ski become positive due to the roll of the sled.

It's better for me to find a good way to make a new subframe that respects the original geometry ...

 

[bholmlate]

Hey Wolfone its never a bad thing when you try as you put it "think outside the box" It always opens the door to new inovations so don't beat yourself up too badly. But it is always wise to respect what has come before. I am sure there was a lot of brain power that was used in the development of the existing subframe. You might as well take advantage of some of it

I think your best bet is to design a subframe the closely resembles what you have now. You might realize through the development if your new subframe that you may be able to make small changes here and there that will improve the finished product.

I am sure there are more then a few poeple in this forum that are interested in and will follow your progress closely to see what you come up with.

keep us all updated on your progress and good luck

 

[ruffryder]

The nytro does not have equal length upper and lower a-arms. The uppers are shorter then the lowers. This allows for camber changes during suspension movement. I believe all the manufacturers design there a-arms similarly.

 

[rlcofmn]

The nytro does not have equal length upper and lower a-arms. The uppers are shorter then the lowers. This allows for camber changes during suspension movement. I believe all the manufacturers design there a-arms similarly.

X2

As Caleb said earlier there are very few vehicles with equal length a arms. but you don't want to run really short a arms.