Double ended Ram mounting and Ackerman.

Mac5005

Mac5005

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Joined
Oct 19, 2005
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Rocky Mount
Starting to build the front axle for my dad. Using one of ecgs ultimate hp60. Using 4wheelsupply arms and knuckle tie in kit.

Psc double ended ram.

The holes aren't drilled in the steering arms so I can put them wherever. The tie in kit allows the arm to be directly over the factor tie rod hole, so that location is available.

My question is this ,

I know the ram mounting location in reference to the tie rod mounting holes, has an effect on Ackerman,

But what's the best way to calculate where to locate the ram forward, inline, or behind the tie rod mounting centerline? And how far offset if so?

I know to match the steering angle with the ram throw, but I'd like to get the best Ackerman I can.

I'm thinking mounting the ram behind the tie rod mounting centerline would create proper ackerman, but how far?

If the ram is mounted in front of the tie rod mounting centerline, farther away from axle, this would be negative Ackerman.

Anyone have any links the address this or solid tech?

I feel like their is a good thread addressing this, but I can't find it.

Thanks.
 
A guy on hardline sent me this. Is this the best way. Theoretically all I would need to do is match the ram throw to the steering angle and tie rod throw, for tie rod mounting location,

Then mount the ram so it's inline with that location and full lock.

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My understanding and practice has been to have the small tie rod in a straight line with the cylinder centerline at full lock. The dual ended ram differs from a standard tie rod in that the overall length changes from lock to straight. It gets longer at full lock than it is straight on, when mounted as mentioned above. My brain tells me it would be difficult to get a true good Ackerman with a dual ended ram because of this, regardless of tie rod end location in reference to king pin. ---more thought on this last sentence in the next post----


But frankly, I don't see Ackerman as a hindrance or benefit off road, especially in low traction and being locked front and rear...Unless you have severely negative Ackerman maybe. Just my opinion.

For a true dual purpose daily driver with selectable lockers, it would help with tire wear while turning, but for the most of us I think we're chasing our tail with automatic lockers or spools, concerning Ackerman.

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thinking some more... in edit or adding to my first paragraph above...

Because the tie rod (dual ended configuration) gets longer at lock, when mounted as described above, that is what gives you Ackerman. Think of this, when the wheels are straight (imagine zero toe in) versus full lock where the 'tie rod' grows, lets use 1 inch.... at full lock, your tires would actually be toed out one half inch each side. Therefore, half inch sharper on inside tire and half inch shallower on outside tire ... that gives you your better Ackerman. How much the tie rod end location is outside of the kingpin, can give you even more... maybe... honestly not sure that matters in this configuration. I think the key is definitely straight line with tie rod ends at lock, giving you a longer tie rod overall.

Secondly. If the ram is mounted behind the axle, (hard to do I know), when tires are straight the tie rods would need to be in - line with cylinder, so that at lock the overall 'tie rod ' would get shorter, to have that toe out condition at lock.


Just late night brainstorming....i could be ass backwards at this point, lol.

Thanks for giving me something to keep me from falling asleep easily Scotty...[emoji23]

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Thanks Matt haha.

My brain was overtime while I was needing to go to sleep also. Only way to slow it down was to post it up lol.


I agree completely with ackerman being less important in our world than on pavement.

Just don't want to make a silly mistake, easily avoidable at this point.
 
As Matt said you want to mount it such that the inside tire turns more than the outside tire. With the ram on the front of the axle you want the tierod inline with the ram on the inside tire side. This is assuming that you are using correct steering arm design for ackermann which is the tierod mount outside the kingpin, like factory.

With the ram in the rear, you want the tierod mount in the arm to be inboard of the kingpin. The one thing Matt didn't mention, you have to be careful to make sure the tierod/arm doesn't become inline during that travel, which can be a challenge if you are trying to get 45+ deg of steering.

I agree that there are many other things more important than ackermann, but correct ackermann does help turning, and if you can design it in, why not.

There was a thread on pirate that discussed and showed the difference between correct and reverse ackermann and how it affected turning angle. Cant seem to find it now though.
 
Glad I stumbled on this thread. My hydro is sitting in the floor waiting to get mounted.
 
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