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ackerman angle

Discussion in 'Center Of Gravity' started by cybrfire, May 11, 2004.

  1. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    How do you calcualte ackerman angle? Or if anybody knows how much ackerman angle is existant on a HP60. considering some different ideas. I have a pretty good understanding of ackerman angle except how to measure it so I know what my impact will be.
     
  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    [Edit] Looking again at your post, I realized I didn't do very well at answering your question. Exactly what numbers mean is probably somewhere in the google results, but I didn't look for it specifically... Sorry... /forums/images/graemlins/crazy.gif
    [/Edit]

    Google is a wonderful thing.

    http://www.login.eunet.no/~einar/mini/acker.htm

    http://www.rctek.com/handling/toe_angle_effect_on_ackerman_steering_principle.html

    And many more.

    Basically, your not going to get decent Ackerman without moving the tie rod to the rear of the axle.
     
  3. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    That is exactly what I'm gona end up doing but the pivot point for the tie rod needs to move 3" or so inboard from where it is now which looks about 1.125" outside the knuckle axis.

    Have you ever welded on a knuckle?
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    No, but it's cast steel which should (theoretically) not be too much trouble. But, I would be very leary of welding anything critical like a tie rod arm onto a knuckle. It would be SO easy to make a small mistake that results in you or someone else dying or being seriously injured. Can it be done safely, I'm sure it can. Would I trust myself to do that, no way... To much stress on the joint and too much risk...

    I would be much more inclined to have a custom arm made that goes on top of the king pin. Still a potential for problems due to non-spec stresses on the knuckle and seat of the pants engineering for most arms, but that would be much more within my comfort zone.
     
  5. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    On a trail rig only why not give it a shot though?
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Maybe, but only if it's a *slow* trail vehicle. I drive my buggy on the dirt roads from trail to trail, often exceeding 40 mph with my daughter in the right seat. I would not be comfortable with that. If you only crawl and only wheel in places where loosing steering is not likely fatal, then I would not hesitate to try it. But I can't help but think of things like Rusty Nail, "The Rim", and such. There your wheeling on a trail right near the rim of a canyon or sheer drop off AND *off camber* toward the drop. A broken steering link in some of those areas (like "No Left Turn") could potentially put you over the side. Some of those scare the stew out of me as it is just worrying about loosing a bead or tie rod end, I don't want to worry about welded knuckles too...
     
  7. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    Not sure if I want to do it or not just want to fully investigate the possibilities. Basically what could be done is swap the left for the right knuckle and so on. Build the tie rod mount off the existing one. The only reason I'm even considering it is because I want to go full hydro steering and have the cylinder behind the axle as opposed to in front of it. You could attach the cylinder to any aftermarket steering arm on both sides but when considering the forces generated by full hydro steer i have to be concerned about how that force is applied to the knuckle. I guess my next option is to go ahead and place the cylinder in front of the axle and "skid plate" it up pretty good so that its less likely to get damaged. I've been talking to the boys at ORD a little bit about this as well. They did the skid plate option. They didn't say the other way was a bad idea but things to consider.
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I agree, full hydro on top mounted arms with Ford knucks would be too likely to be breaking them. Have you looked at Deden Bair? (sp?) They have VERY heavy duty knucks that are keyed, provide for extra studs, and support rear tie rod configs. In any case, lots of guys, including competitors, run the rams in front with no issues. I would not hesitate to run these with top arms and full hydro… Seems like the rear steer arms for the DBs have fairly good AA too.

    Oh, one other thing. Most people feel that AA is not worth worrying about in a 4x4. But IMO, if you can get something close without too much trouble, that would be a good thing. Me, I’m not interested enough in it (for the gains I would expect) to fool with it. I also didn’t think high steer was worth it, so I have a low tie rod with my ram right between it and the axle. 2 years like that and I’ve yet to damage the tie rod or ram. And the tie rod has been hit hard enough that the noise it made caused someone driving about 50’ in front of me stopped to see what had happened. Still so straight it would make a pool cue stick jealous…
     
  9. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    Still more to think about. I have looked at the aftermarket knuckles and I guess I will leave things as they are for now and if damage becomes an issue I may upgrade to those knuckles. Not sure if AA is that important offroad either. I do believe it would be an issue if the knuckles were just flipped around and ran that way. I'll post some pics when I get where I'm going. /forums/images/graemlins/thumb.gif
     
  10. unclematty

    unclematty 1/2 ton status

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    If I understand you correctly, your having a problem with the difference of the two measurements. I wonder if you could measure from a point on your frame, to the wheels and come up with the measurement. then just move the measurement to the rear of the axle. AS for the welding, if you can heat the knuckle toglowing red before/during the welding you shouldn't have a problem. that way the welding won't disrupt the grain of the cast steel. Hope that is what you are after. /forums/images/graemlins/whistling.gif /forums/images/graemlins/hack.gif /forums/images/graemlins/weld.gif /forums/images/graemlins/grind.gif
     
  11. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    This is basically what I have figure out.

    [​IMG]

    This is on a high pinion furd d60

    ackerman angle is the relationship between kingpin axis and tie rod mounting location. In front of the axle the tie rod mounts outside the kingpin axis allowing for ackerman angle. Problem is to put a hydraulic cylinder in front of the axle you either have to build alot of protection around it or run the risk of damage.

    If you flip the knuckles side for side you could put the cylinder under the axle but this throws the ackerman angle way out of wack and you would be getting alot of "push" from the front axle when turning. To fix this you would need to move the pivot point for the tierod 3.3 some odd inches inboard. This would require welding to the knuckle and as stated above is it worth the risks involved? Or lay out heavy green to dedenbear knuckles. This ackerman angle is figured on a 115 inch wheel base where my rig is.
     
  12. miniwally

    miniwally 1/2 ton status Premium Member

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    I have Howes double ended ram mounted in the front of my Ford 60 with a nice tube and plate guard for it. I have actualy really liked it because it acts sort of like a ramp for the front axle to slide over things that I belive would normally hang up on the axle tube. I reamed the tie rod holes out to mount the tie rod on top of the stock location. The ford tie rod mounting locations are higher up than the Chev. tie rod mounts. Be careful about the ford knuckles because they are prone to breaking, I think only when used with a high steer arm though.
    If it was me I would seriously look at leaving things as they are and mounting a ram up with a good guard.

    My .02
     
  13. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    That is where I am now. Knuckles are back on in the factory positions so I will have to fab up some kind of gaurd when I get to mounting a double ended ram.
     
  14. Triaged

    Triaged 1/2 ton status

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    Take a look at the "Ackermann.zip" file. I didn't make that one (it is from RaceTech), but have had good luck with it.

    Did you by any chance measure the stock Ackermann?

    Edit...maybe I should have posted the link /forums/images/graemlins/blush.gif
    http://home.earthlink.net/~triaged/Files/
     
  15. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    I did some figuring on it and the factory ackerman isn't very close either. Unless your wheelbase is some 220 plus inches.
     
  16. Triaged

    Triaged 1/2 ton status

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    I figuered that...Never did any measuring but it sure does look close to parallel steer.
     
  17. ntsqd

    ntsqd 1/2 ton status

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    Some Ackerman is probably good. Road Racers want the Ackerman Intersection Point (AIP) to be somewhere btwn the rear axle CL and 50% of the wheelbase. I can see binding up a locked-up rig getting easier and easier to do the further forward you move the AIP. Conversely, moving the AIP further and further to the rear of the rear axle CL probably promotes binding too. At the rear axle CL is my SOP sweet spot guess.
     
  18. TorkDSR

    TorkDSR 1/2 ton status

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    i cant quite figure out why we, as offroaders, are so concerned.

    the truck is gonna follow the path of the tire with the most contact pressure...

    what am i missing.
     
  19. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    Your missing cruise night and the occasional trip to the local trail without the trailer. Other than that not much.
     
  20. TorkDSR

    TorkDSR 1/2 ton status

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    without the trailer.... good one /forums/images/graemlins/histerical.gif

    ok, thanks... just checking to see if there was some deep meaning i wasnt seeing
     

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