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Old 11-06-2007, 08:43 AM   #1
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Default Why are buggies built this way?

I guess I tend to over-analyze things... but maybe one of the manufacturers will see some of this and put it to use...

1) Why is the ackerman plate and related steering linkage stuff on top? Why not put them down in the chassis, UNDER the front driveshaft? It would help lower the CG AND help prevent some of the slop in the steering.

2) Why doesn't everyone make the center diff mount in such a manner that you can remove the top portion with the brakes still assembled, leaving your setup intact? Mugen does this, but some of the others don't. I even thought putting the brakes UNDER the diff would be a good idea, until I looked at how complex the linkage would get... lol

3) Why don't they make a "quick change" gearbox case/bulkhead/whatever you want to call it? Make it so the hing pins remain in place and you simply remove the top of the section at the front or rear of the car. MUCH easier to change diff fluid for different track conditions! Put the swaybar to the inside, not hanging out front or in the back to further simplify matters. It would be nice if changing a front or rear diff was as simple as changing the center diff.

4) What's the deal with hump packs? The stick pack batteries, especially if you lay them down, would lower the CG of the car. For that matter, make it so the mount is somewhat adjustable to allow weight bias to be adjusted front to rear.

5) While Losi had a good idea in reversing the way the teeth face and keeping the pinion on the same side for the front and rear diffs, I don't personally think they took it far enough. Offset those gears further to keep the driveline STRAIGHT. Put the pinion in the same spot on both ends, and build the ring gear so it is offset enough to clear the difference- offset to the inside on the rear and to the outside on the front. Less wear on the CVA's.

6) This is specific to pivot-ball cars: Why not use spherical rod ends with bolts to retain them instead? Make an "E-hub" so the rod are sandwiched between portions of the hub, so the retaining bolt is ONLY loaded in shear.
Spherical rod ends will take huge loads, and virtually no wear, so no slop and inconsistancy.

Ok, enough of my rambling for now. Anyone else have any ideas to improve buggy technology? This stuff almost makes me want to design one myself, and find some third-world country to set up manufacturing in.
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Old 11-06-2007, 09:26 AM   #2
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your #3 is the one that I have thought about the most. When I changed the diff fluid in my RC8, I was so nervous because I hadn't done it before. It's such a PITA and I'm sure they could have easily designed the gear boxes differently but maybe there's a reason they didn't? who knows.
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Old 11-06-2007, 09:52 AM   #3
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#1 a. So the steering hardware can be taken off without disturbing the drive line. b. so the movement of the rack when the servo saver happens has a place to happen. c. correct geometry.

#2 Why doesn't everyone make a split center diff mount. I'd settle for that.

#3 I think the common arrangement is about as good as it gets. Maybe setup the hinge pins so that a screw or nut could be removed from the end to allow the case to slide off the back or front. I think it is more of a what has to go where issue. There are alot of things connected to the gearboxes and giving them their own structures would further complicate things.

#4 This is purely because of the length of the area available in some cars. I bet in a few years we'll be using some sort of lipo battery that's about the size of a quarter.

#5 I think again, this is about what must go where. I thought the same thing but I couldn't see how the steering linkage could be made to clear the offset front drivetrain. As it is now the drive shaft must enter the center for the front gearbox.

#6 Look up Crono cars, they have something similar to what you're refering to here. They are successful in Europe and Asia but have not caught on here.
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Old 11-06-2007, 10:24 AM   #4
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#1 I don't see how keeping the steering components the same but lowering the plate (i.e. makign the arm on the bellcranks at the bottom/flippign the bellcranks upside down) will reduce the steering slop any. If the plate was super low/on top of the chassis, then the plate/steering links would hit the track when the car is bottomed out and landing at an angle.

#3 Not a bad idea to make the bulkhead open from the top like the 4wd electric BJ4/B44, NTC3 cars do but it would be as much ro more work possibly as you would now have to deal with the shock tower/camber links, and shocks as being the things in the way when removing the top of the bulkhead.

#5 To off-set the driveshafts isn't that easy. They need to be on one side of the front diff and the opposiet side of the rear diff to make the f/r wheels spin in the same direction...otherwise you'll have the tires fighting one another spinning against themselves. Then to off-set the driveshafts you are limited by the steering parts or other parts within the chassis that pretty much have a standard size (Rx batteries) which limit the room you have to play with.
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Old 11-06-2007, 10:30 AM   #5
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Hmmm... interesting points... however:

1: a) It could be slipped out the side, no problem there. b) with that arrangement the rack wouldn't move, the servo saver would be "upside down." It would be more rigid. c) Perhaps that is the issue. I need to look at that some more.

2: Maybe the aftermarket can offer a solution there. That one isn't rocket science!

3) The gearboxes already are their own structure. I was thinking more like 3 parts instead of 2, with the "outer" (i.e. front of the front or rear of the rear- will just refer to this as the "front" for now) being split above the line where the hing pin holders attach. The bottom stays in place with the hinge pin holder attached. It would be a few more screws... but a lot less work to change. Remove 4 or maybe 6 screws, take off the upper portion of the "front" of the gearbox case and slide the diff out like now, without disturbing the suspension components.

4) Ok, that makes sense... I'm not saying it could be done in ALL cars with the current layout, more that it is a part of the original layout that should be addressed. As for using tiny little LiPos... maybe you are right. Technology advances pretty rapidly.

5) What if the driveshaft were OUTSIDE of the servo saver post? Just thinking "outside the box" here.

6) I'll have to look that up.
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Old 11-06-2007, 10:36 AM   #6
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1. Buildup of dirt would cause binding and removal of the driveshaft would be even more difficult.

2. Mugen, Xray, Jammin? Kyosho? . Only car Iv'e seen that doesn't have a split center diff is the Losi.

3. My Savage X has easy access diffs, the hinge pins are untouched when removing the diffs.



5. I thought the same thing with the Losi, why not put both pinions in the same spot? Diff cases could be the same f/r, same gears too. Would there be clearance issues with the steering?
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Old 11-06-2007, 10:59 AM   #7
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Good discussion!

I was thinking about the current state of buggy design just yesterday, and was pondering 'alternative' chassis designs for Buggies...

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Old 11-06-2007, 11:55 AM   #8
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Quote:
Originally Posted by xrayeddy View Post


5. I thought the same thing with the Losi, why not put both pinions in the same spot? Diff cases could be the same f/r, same gears too. Would there be clearance issues with the steering?
Your front diff would spin backwards.
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Old 11-06-2007, 12:01 PM   #9
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The biggest opportunities are the engines. What about a compact lay down 4 stroke engine with a shrouded cooling fan? How about helical cut gears so the drive shaft could be run above it's current location and everything else could be flat on the chassis? For that matter, revo style inboard shocks (now that the drivetrain is out of the way)?
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Old 11-06-2007, 12:53 PM   #10
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OMG!!!!!!!!!!! someone needs to design their own car and see how they fair....
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Old 11-06-2007, 01:48 PM   #11
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Quote:
Originally Posted by Maybell View Post
OMG!!!!!!!!!!! someone needs to design their own car and see how they fair....
You know, I would do just that... however, the finances to do that are a little (ok, a lot!) out of reach.

Designing it isn't an issue... getting it produced is. (Not to sell the guys that DO design these things short- there's a lot of thought that goes into them initially, and a lot of testing and further development afterwards.)

Specifically all the one-off stuff to prototype a new design is expensive. It is cheap to produce lots of parts, expensive to produce just one. Not in materials, but in labor hours to produce prototype parts by hand, or to program CNC machines for what may turn out to be only ONE part...

The obvious answer of course is to use as many "off the shelf" parts as possible. Get the concept working, then worry about producing your own version of those parts. The expensive parts to produce initially would be things like differentials, spur gears, ring and pinons, and CVAs. Lots of machine work in those itty-bitty parts.

I DO have connections that would probably be adequate to smooth over the process of a startup in Southeast Asia, but no way to finance it. (No, I'm not fishing for that...)

Just FYI though, this wasn't a discussion about designing a whole new buggy. This was a discussion about what could be improved on the current crop, either by the manufacturers, or by aftermarket replacement parts.

And it is "fare," not "fair" in the context you used. I suspect I would FARE better at designing a buggy than you would in an English class. If you are going to heckle, please learn how to use the language.
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Old 11-06-2007, 02:00 PM   #12
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P.S. It wouldn't be the first time I had made something I wanted for an RC car, or modified an existing part to accomplish a specific goal.

I'm currently thinking REALLY HARD about chopping up some Losi center diff mounts. I'm annoyed by the current arrangement. I'd have to use 2 sets to make 1 set of 2-piece mounts, but it might be worth it... it would keep me entertained for an evening, and I get to play with power tools.

Of course there is a company that offers that already, but at $68.xx per set they're a little pricey, and look somewhat heavier than the stock setup. (Now if I figure in my hourly rate for my salary, well... playing with the power tools would be more expensive... but we don't count hours spent on a HOBBY do we?)
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Old 11-06-2007, 02:03 PM   #13
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Quote:
Originally Posted by Jack Smash View Post
Your front diff would spin backwards.
Jack, not if the ring gear is reversed. It depends on which side of the pinion engages the ring gear. That's why offsetting the ring gear was mentioned previously.
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Old 11-06-2007, 02:04 PM   #14
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Intersting post i like it
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Old 11-06-2007, 02:13 PM   #15
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Quote:
Originally Posted by xrayeddy View Post
1. Buildup of dirt would cause binding and removal of the driveshaft would be even more difficult.

2. Mugen, Xray, Jammin? Kyosho? . Only car Iv'e seen that doesn't have a split center diff is the Losi.

3. My Savage X has easy access diffs, the hinge pins are untouched when removing the diffs.



5. I thought the same thing with the Losi, why not put both pinions in the same spot? Diff cases could be the same f/r, same gears too. Would there be clearance issues with the steering?
1) Good thought. I don't THINK that is correct, but it is worth consideration.

2) Yes, and it annoys the crap out of me.

3) I would be interested in seeing that. Got pics?

5) It isn't QUITE that simple, but the concept is what we are talking about essentially. The easy way looks to me like a different differential case, with the ring gear mounted on a flange of some sort, so it can face either way but offset. Of course that means the differential would have an extra part, but then the same parts could be used at both ends, with the ring gear moved.

Losi ALMOST did what we are talking about. The diffs face the same direction on both ends, just the ring gear is different. The front gear faces the center of the diff, the rear one faces the outside. They still ended up with a VERY abrupt angle on the front driveshaft due to the method they used. This could be done better... but not in the current chassis layout. Of course it would also be possible to simply use the same setup on both ends, with another pair of gears to reverse the rotation, but why add complexity?
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