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03-26-2011, 09:23 PM
| #81 |
| Suck it up!   Join Date: Mar 2008 Location: Arkansas
Posts: 11,652
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Nice diagram.  However, just so no one gets confused, it needs to be said that the center of gravity is NOT always where the balance point is. I only bring this up because the cg points on the diagram are pretty much where all the rigs in this thread have their balance points. It would also be useful if we had instructions on how to find center of gravity. |
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03-26-2011, 09:49 PM
| #82 | |
| Pebble Pounder Join Date: Mar 2011 Location: SLC UT
Posts: 133
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Your right. The CG is a 3 dimensional property, you need to basicaly find the balance point in all 3 directions and then find where they intersect to get a center of gravity. My diagram only shows 2 dimensions and it assumes that from the width of the crawler its even on both sides and straight down the middle. As for being able to find the center of gravity, thats a tough one since in some cases it will be at a point where there might not be any material where you can balance it. There might be a way to find it by doing weight ratios in 3 directions, people in this thread have mentioned that they know that they run a 60/40, if you can also tip your rig on its side and measure the weight top to bottom and measure the weight from left to right... might be extremely difficult to do though I'm not sure, I would be interested in the top to bottom balance point for sure if anyone has a scale and can try it... | |
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05-30-2011, 02:16 PM
| #83 |
| Newbie  Join Date: May 2011 Location: Thomasville
Posts: 21
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Well, I've been lurking for a while and am in the process of designing a custom scale crawler from the ground up. Before I found RC crawling I was making plans for a 1:1 crawler. In that research I've found something that may be quite useful to this thread. I think true CG has more of an effect on crawling than a balance point since it is an actual point on the 3D plane. I'm sure with a little tweaking, this spreadsheet and site could be a very valuable asset to someone really wanting to improve their crawler by finding their exact CG. http://www.jeepaholics.com/tech/cog/ |
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05-30-2011, 04:09 PM
| #84 |
| I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA
Posts: 8,314
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CG has a relation when going vertical. balance point is more horizontal. Both are important. You want both as low as you can go while still allowing clearance over obstacles. Front bias (60/40 vs. 70/30) helps as well. Whenever you fix one issue, you likely FUBAR another..........   "The only thing perfect is a A'hole, just ask one!" Shrug. |
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06-01-2011, 11:06 AM
| #85 |
| Rock Stacker Join Date: Dec 2010 Location: Toronto
Posts: 76
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Another thing to consider (but not lose sleep over) is weight distribution. For example, think of a barbell with a 5lb weight on each end. Now imagine sliding those weight to the center of the bar so they touch each other. Both scenarios have exactly the same total weight and center of gravity, however due to moment of inertia they will handle very different. This is more pronounced with high speeds, but does come into play when a crawler is at the tipping point over a ledge. |
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06-01-2011, 03:25 PM
| #86 |
| Rock Crawler Join Date: Jul 2007 Location: Portland,OR
Posts: 888
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Here's a pretty neat calculator for real rigs. Just increase all measurements by 10, then reduce the results by 10. The rollover angles are really accurate ( remember to reduce then increase results by 10) as well as the Center of Gravity, Instant Center, Roll Center and Slope, Squat / Anti Squat and other measurements. Even has a 3D model. You can even find break/shear points of your links and whatnot as well. Suspension and CG Caluclator Last edited by solomon7; 06-01-2011 at 03:29 PM. |
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06-01-2011, 04:52 PM
| #87 | |
| Quarry Creeper Join Date: Feb 2009 Location: French Guiana
Posts: 433
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Hello, Quote:
Initially, it is necessary to find the balance point. I did not put a body on my pics, but it is necessary that the crawler is RTR (body, lipo…)  One traces a vertical line passing by the balance point.The centre of gravity is on this vertical red line (but where  ).  It is necessary to remove the front OR rear wheels (rear wheels is better). And to make rest the crawler on threadings of wheels, so that it can be balanced. The removed wheels do not modify balance, except if they have mobile weights.  You hang a plumbline with threading of the wheels. To be more precise, I place 2 plumbline, one on each wheel of the axle.  The centre of gravity is with the intersection of the red line and the plumbline. To check, you can make the same thing with the other axle of the crawler, the 3 lines will cut yourselves at the same point : The centre of gravity.  In my case, the balance point and the centre of gravity are very close. It is preferable that the centre of gravity is lower than the balance point. Easy Last edited by TotoRax; 06-01-2011 at 04:55 PM. | |
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06-01-2011, 05:56 PM
| #88 |
| Suck it up! Join Date: Mar 2008 Location: Arkansas
Posts: 11,652
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Very nice. Simple too, thanks. |
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06-23-2011, 06:18 PM
| #89 | |
| Newbie Join Date: May 2011 Location: Thomasville
Posts: 21
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Very Nice! How about COG on the Z axis? (side to side) Quote:
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06-26-2011, 08:58 PM
| #90 |
| I wanna be Dave Join Date: Aug 2004 Location: central VT
Posts: 2,300
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My AX10 has it's balance point about 1/4 in front of the lower link mounts on the chassis. It is actually balancing on the botom of the battery tray, which is ziptied to the upper links. No added weight in the wheels, which are about 6 ounces a piece.   Not sure on the height of the COG, but it will stand up on its side. |
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