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10-22-2007, 09:17 PM
| #1 |
| Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada
Posts: 308
|  Ackerman Steering with Locked Diffs
Hi everybody. I was wondering if someone who knew more about car steering could help me answer this question. When turning corners on pavement you need both ackerman steering (to compensate for the different geometries of the two steering wheels) and an open differential (to compensate for the differences in speed). If you don't have these then the wheels skid when you turn. What if you had a steering servo for each steerable wheel (rather than ganged) and a computer to control both to get ackerman steering. Would it be pointless if you didn't have an open differential since the wheels would still skid due to the speed difference? Except that now they have no more side-skid (they only skid along the steering circle rather)? I think it might improve control (and maybe reduce axle stress) but I'm not sure. I know the ackerman is pointless when you're on rocks but I'm talking about pavement. THanks! Last edited by DKNguyen; 10-22-2007 at 09:24 PM. |
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10-22-2007, 09:52 PM
| #2 |
| I wanna be Dave Join Date: Oct 2005 Location: Columbia TN
Posts: 6,154
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Are you planing to crawl on pavement????
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10-22-2007, 10:03 PM
| #3 |
| Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada
Posts: 308
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If that's what the robot encounters, that's what the robot must pass.
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10-22-2007, 10:29 PM
| #4 |
| Quarry Creeper Join Date: Jun 2007 Location: Torrance, CA.
Posts: 282
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The ackerman effect happens when caster is added to the front axle. What this causes is the inside rear tire to lift while the vehicle is turning. It is a very simple. There are two things to increase rear wheel lift: -Add more caster. But this also increases the amount of camber that is gained while turning the wheels. -Space the front tires further out on the spindles. I would research the effects of Caster and the ackerman effet by reading through some Kart articles. My Swiss Hutless would lift the inside tire about 3"~4" without someone in it. Edit: http://www.sniper.com.au/kartoztech2.htm Last edited by _BEN_; 10-23-2007 at 10:52 AM. |
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10-22-2007, 10:46 PM
| #5 |
| Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada
Posts: 308
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Is it even possible to add caster with a CLod axle tube?
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10-22-2007, 10:58 PM
| #6 |
| I wanna be Dave Join Date: Aug 2006 Location: under a rock and a hard place
Posts: 5,443
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change the length of your links or clock the axle C's/tubes if you have steel ones
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10-22-2007, 11:21 PM
| #7 |
| REST IN ALOHA CHIP   Join Date: Nov 2005 Location: *
Posts: 3,549
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wow a pavement crawling clod robot, whats next? maybe you should check www.pavementcrawler.com |
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10-23-2007, 03:48 AM
| #8 | |
| Quarry Creeper Join Date: Apr 2007 Location: Kapahulu Safeway
Posts: 281
| Quote:
 . I actually tried to follow the link | |
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10-23-2007, 03:58 AM
| #9 |
| REST IN ALOHA CHIP Join Date: Nov 2005 Location: *
Posts: 3,549
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10-23-2007, 03:59 AM
| #10 |
| MWRCA'er  Join Date: Apr 2004 Location: Machesney Park IL
Posts: 3,995
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10-23-2007, 10:09 AM
| #11 |
| Rock Stacker Join Date: Sep 2007 Location: French #70 living in Toyohashi
Posts: 67
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You do know that ackerman steering is acomplished by simple mechanical geometry arrangement ?
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10-23-2007, 10:47 AM
| #12 | |
| Quarry Creeper Join Date: Jun 2007 Location: Torrance, CA.
Posts: 282
| Quote:
Clock the axle to about 85° (If you are running a 4 link just use shorter top links) | |
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10-23-2007, 11:49 AM
| #13 |
| PapaGriz Yo   Join Date: Apr 2004 Location: In the garage building the wife a crawler
Posts: 13,137
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Behind the Axle (BTA) is the best way to correct the Ackerman on a Clod. This actually gives you too much but it's better than the stock setup with the steering arms out front. Leave the tie rod behind the axle on the rear axle. Ben, I really wouldn't expect to see any weight jacking or weight transfer in a slow speed crawler. |
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10-23-2007, 12:26 PM
| #14 |
| Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada
Posts: 308
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That's a neat product. I still might try and go with double servos though just due to wanting to stick some antenna on the knuckle steering mounts as well and with double servos you get independent antenna that can face in different directions.
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10-23-2007, 01:07 PM
| #15 |
| owner, Holmes Hobbies LLC  Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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With locked diffs it wont matter anyway. The inside tire wont be able to turn slower than the outside so you will get skidding.
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10-23-2007, 04:03 PM
| #16 |
| Rock Crawler Join Date: Oct 2007 Location: richmond, va
Posts: 766
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the new e-maxx have two servos in the front one for each wheel
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10-23-2007, 08:56 PM
| #17 | |
| Newbie Join Date: Sep 2007 Location: Hot Springs
Posts: 29
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10-31-2007, 10:14 AM
| #18 | |
| Newbie Join Date: Apr 2007 Location: Malaysia
Posts: 18
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11-03-2007, 11:53 AM
| #19 |
| Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada
Posts: 308
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If you only had one, ackerman, or differentials, would have better performance in steering?
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11-06-2007, 08:37 PM
| #20 |
| Newbie Join Date: Apr 2007 Location: Malaysia
Posts: 18
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With Ackerman and open diff - best for pavement only With Ackerman and lock diff - best for rock crawling but still perform well on pavement in term of steering control since there is no side-skidding Without Ackerman (parallel steering arm) - acceptable steering performance on rock (with locked diff) and pavement (with open diff). With negative Ackerman (stock setup) - worst steering performance for rock and pavement . It may help a little bit if you have open diff but you cannot overcome most of the obstacles. There will be a lot of stress on your steering servo, axle tube and axle C etc. IMHO |
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