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Old 12-04-2007, 12:36 AM   #1
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Default JRX-S based 4wd buggy?? Why was the idea scrapped?

I had read earlier in one of the forums that Losi had been experimenting with a JRX-S based 4wd electric buggy. Did anything ever come of that or was that a one-time deal with custom parts and never looked at as a feasible design again?

I think that having a design with the battery in the center (like a 2wd) car would be fantastic.

Has anyone thought about possibly experimenting with a JRX-S and getting longer arms and shock towers and turning it into a buggy? Anything else that would have to be updated initially? May have some problems with debris getting into the drivetrain that would have to be looked at.

Very interested in this possible project and seeing where it goes.

If anyone has a picture of the JRX-S 4wd buggy that was custom built previously, please post as well.

Thoughts? Comments?
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Old 12-04-2007, 01:11 AM   #2
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I was kinda wondering that a few days ago also. Maybe if they put out a list of the parks they crossed between the JRXS, the xx-4 and teh xxx-4, someone could make their own JRXS Buggy.
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Old 12-04-2007, 01:16 AM   #3
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It's going to be like the xxx-4, an onroad car changed to offroad.
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Old 12-04-2007, 04:00 AM   #4
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The best performing buggies are one off designs specifically for offroad. TC conversions will never perform as well and typically aren't as durable.
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Old 12-04-2007, 04:08 AM   #5
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Because last time they did that they failed - XXX-S to XXX-4
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Old 12-04-2007, 06:23 AM   #6
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This car was a prototype at the 2005 ifmar worlds. Travis Amezcua, and Jesse Robbers had them, and I believe maybe one other Losi driver. They got them shortly before the worlds, so they didn't have enough knowledge of the cars setup wise to make them work good enough to be competitive. So they ran their "Fall Back" cars instead (XX4, XXX4). Could the cars have been competitive with more time on them? Maybe, but they didn't have more time. Would Losi have ever made it into a production car? Maybe, if they had more time to work on the car before the worlds, thus making them compititive at the worlds. Would the car have worked on anything but the smoothest of surfaces? Probably not, the inner hinge pins on a JRX-S are far apart because of the offset of the diffs, which is done because the belts have to go some were when they placed all the weight down the center, which for a touring car works great i.e. short suspension arms means a car that will react faster, also it puts more load on the tires (think see-saw center pivot is like the inner hinge pin, the closer you move to the center (shorter a arm) the harder you have to push down to lift the same weight on the other side (rest of chassis weight)), the short a arm also worked well on the JRX-S because of the centralized weight. Now the same could be said for the JRX-4 (thats what people were calling it), but the problem was in off-road suspension is used for tuning the way the car turns (like on-road), but it also has to absorb the bumps (I know on-road tracks aren't perfectly smooth, but they are alot smoother than off-road tracks), and landings from jumps. The JRX-S doesn't have much wheel travel (obviously, it's an on-road car), however the JRX-4 would need a lot of wheel travel, and with shorter a arms it would have caused a lot of wheel scrub. I don't know if that's the exact term for it, but this sweet pic that I made should illustrate it pretty well. This would cause the tires to be pulled in towards the center of the car as it landed from a jump. This would probably make the car VERY unstable as the suspension moved. I don't think it would have been a very good car for anything but the smoothest, high traction tracks. Hmmmm, sounds like the XXX-4, I guess Losi didn't want to go down that road again (on-road car turned off-road). Anyway, here for your viewing pleasure are all the JRX-4 pictures I could find. I still love seeing prototype stuff.
Attached Thumbnails
JRX-S based 4wd buggy??  Why was the idea scrapped?-prototype.jpg   JRX-S based 4wd buggy??  Why was the idea scrapped?-losifrsusp.jpg   JRX-S based 4wd buggy??  Why was the idea scrapped?-losi-4wd-1.jpg   JRX-S based 4wd buggy??  Why was the idea scrapped?-losi4wd2.jpg   JRX-S based 4wd buggy??  Why was the idea scrapped?-short-vs-long.jpg  

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Old 12-04-2007, 06:24 AM   #7
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Last 2 pics. Enjoy
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JRX-S based 4wd buggy??  Why was the idea scrapped?-losi4.jpg   JRX-S based 4wd buggy??  Why was the idea scrapped?-losi3.jpg  
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Old 12-04-2007, 08:40 AM   #8
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Ive thought about a similar design for years. the only way i figured it would work is to center the differentials like the xx4 & xxx4 so the suspension can have the same travel & somehow run the belt over the chassis components. this would be the tricky part requiring a few pulleys.

heres a pic i made to illustrate it.
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Old 12-04-2007, 08:47 AM   #9
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Quote:
Originally Posted by baruke1 View Post
Ive thought about a similar design for years. the only way i figured it would work is to center the differentials like the xx4 & xxx4 so the suspension can have the same travel & somehow run the belt over the chassis components. this would be the tricky part requiring a few pulleys.

heres a pic i made to illustrate it.
Far too many belt angles/wrap in that.

If you want to acheive a narrow-diff, central battery car you need to look at what Team Magic have done with the E4 - it is a 3-belt system quite similar to what is used in 1/10th nitro.

The XX-4 is also 3 belt so there is no reason why it couldn't work if done right. Power and runtime is not a problem in modified 4wd now.
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Old 12-04-2007, 08:53 AM   #10
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The real question is losi even gonna try with a new 4wd?With this class growing will losi stay out of it?Its a shame if they do.
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Old 12-04-2007, 09:17 AM   #11
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Have you looked t the XXX4 or the X5's belt?
Yes it looks like is a lot but its only 2 pulleys more than the xfactory x5 and some people are adding belt pulleys to their x5 for more belt tension adjustments. I thought of using 3 belts too like the xx4 but that would leave little room for the steering rack with the battery and the motor in the center of the chassis. Also, im not sure how the rear end of that drive train would fit, although it might be the way to go I still think the single belt over the components is what is needed to achieve what we are looking for in this design.
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Old 12-04-2007, 09:44 AM   #12
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Thumbs up JRX=4 .

IFUONLYKNEW !those are some good shots of that car little wider shock towers and arms it would be set to go,down travel?
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Old 12-04-2007, 09:45 AM   #13
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Woke up this morning and got a chance to read all the posts on this thread. I like the information that is being spread around. Thanks for the pictures as well.

I guess it wouldnt be feasible to use the XX4 (front) and XXX-CR (rear) arms on the JRX-S chassis due to having too wide of a car correct?

Moving the diffs to be more centralized on the chassis and having the batteries run down the middle is still very challenging.

Anyone have any pics of the Team magic sedan that is being referred to to show their 3-belt design with the batts down the middle?
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Old 12-04-2007, 10:13 AM   #14
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Here it is.


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Old 12-04-2007, 10:24 AM   #15
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You could possible use the XX-4 drive train on a new chassis and move the long rear belt and put it in the center and the short side belt and put it in the rear. That's over simplifying the complexity of that change but if you had the tooling available, it could be done if you just had to get the batteries down the center or near the center like the Team Magic car. I'm not sure that would buy you much. The blance of the XX-4 is great and one of the reasons it has done very well over the years.

IMO the The X-Factory X-5 single belt is how Losi should have approached their new 4wd when they began work on the XXX-4. They choose to take their XXXS touring car and convert it for the XXX4. They should have worked from their proven XX-4 (of course that's my opinion). The X-5 kept the kept the XX-4 balance and the two cars drive very similar yet the X-5 accelerates much harder. The extra pulley they added recently in the X-5 Squared effectively opens up the Z-bend making it a bit more efficient and easier to adjust the tension.

With the JRX-4 prototype you could use smaller pulleys (that would take away the efficiency of the drivetrain) and use longer arms. The HPI Pro 3 had fairly long arms with wide diffs. However you would still be using short dogbones which will scrub in the out drives much more so than longer dogbones. This alone will not allow the car to be as good in the bumps. Also with the wide diffs it would be hard to fully seal the drive train. This would create a maintenance headache that other cars on the market do not have.

I'm glad Losi didn't do much with that prototype.
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