164LikesTamiya XV-02
03-21-2022, 10:13 PM
#61
- - -
Anyway, I called it with the slipper clutch. Nice to see a center diff will also be an option, though I doubt it will have a significant benefit due to the tiny tires and equally-tiny traction that those tires have. Rally cars aren't like monster trucks that have big meaty tires that can really bite into the ground -- they mostly just skip along the surface.
The ball diff is an interesting anachronism. It might be okay for on-road driving, but I'd stay away from it for anything involving dirt. Bulkhead flex will inevitably let some amount of dirt into the diff cases over time, and ball diffs can't be sealed. Not to mention, ball diffs get chewed-up super fast from the constant driveline shocks experienced by off-road RCs.
03-21-2022, 11:01 PM
#62
Ah fyrstormer, the forum bench-racer.
It comes with a direct center "spool". Slippers and center diff are options. Plenty of shaft drive 4WD buggies in the past using ball diffs with plastic bulkheads with no dirt making its way inside.
It comes with a direct center "spool". Slippers and center diff are options. Plenty of shaft drive 4WD buggies in the past using ball diffs with plastic bulkheads with no dirt making its way inside.
03-22-2022, 06:50 AM
#63
Tech Master
Thread Starter
03-27-2022, 12:56 AM
#64
I'm glad you've had good luck with ball diffs not getting contaminated when running off road, but that doesn't mean everyone has. And I notice you didn't address the point I made about ball diffs getting chewed up from driveline shock when driving off-road. That's cool though, I understand the urge to cherry-pick when arguing.
03-27-2022, 01:02 AM
#65
Still waiting for the maths that says that a higher CG is better. It's been contended several times in this thread that "it's different", or "it's complicated". I contend very simply that it is worse.
In fact, instead of writing lengthy posts containing information about full size cars that I already know, all you have to say is "I'm willing to accept the higher CG because I'd like to try a centre diff. And because it's a Tamiya".
That's what it comes down to - these rally cars aren't raced (except for in a handful of cases), so it doesn't matter whether they handle well. It's just Tamiya being Tamiya, larking around in the design office, and releasing it to a willing public that will buy them to build and put on a shelf.
In fact, instead of writing lengthy posts containing information about full size cars that I already know, all you have to say is "I'm willing to accept the higher CG because I'd like to try a centre diff. And because it's a Tamiya".
That's what it comes down to - these rally cars aren't raced (except for in a handful of cases), so it doesn't matter whether they handle well. It's just Tamiya being Tamiya, larking around in the design office, and releasing it to a willing public that will buy them to build and put on a shelf.
Originally Posted by fyrstormer
Lower center of gravity is always better, but it's not a concern on rally cars, so it doesn't dictate the design. Hence they decided to stand the battery on its edge to free-up chassis space for other components. Similarly, drift cars nowadays intentionally raise the center of gravity so the chassis will lean when sliding despite having minimal traction.
03-27-2022, 09:16 AM
#66
Tech Regular
03-27-2022, 11:18 PM
#68
03-28-2022, 03:03 AM
#69
Tech Master
Thread Starter
03-28-2022, 08:32 PM
#70
I didn't say anything about which option it comes with. I said I was correct about a slipper clutch being an option. If you look back in the thread, you will see other people were telling me it couldn't be that because a slipper clutch wouldn't fit. Maybe knowing the context of what you're responding to would be a good idea next time.
I'm glad you've had good luck with ball diffs not getting contaminated when running off road, but that doesn't mean everyone has. And I notice you didn't address the point I made about ball diffs getting chewed up from driveline shock when driving off-road. That's cool though, I understand the urge to cherry-pick when arguing.
I'm glad you've had good luck with ball diffs not getting contaminated when running off road, but that doesn't mean everyone has. And I notice you didn't address the point I made about ball diffs getting chewed up from driveline shock when driving off-road. That's cool though, I understand the urge to cherry-pick when arguing.
You state something as if it happens often or you know better than RC engineers. Cherry pick? How about you saying Arrma is not durable because of an old Raider that you used to own. Basing it entirely on one vehicle? Sounds like cherry-picking to me. Crazy thought but I do not disagree with you on everything, hard for you to understand?
Have had plenty of "offroad" cars with ball diffs, running way more abuse and never in my 20+ years in the hobby have seen anyone say, "my ball diff failed because so much dirt went inside due to bulkhead flex". Even if that much dirt somehow made it past the outer bearing, you're more likely to kill a ring and pinion gear first. The main reason why gear diffs are mainstream now in offroad is due to the much higher power with brushless motors and increased traction, not due to "driveline shock" from offroad conditions.
03-28-2022, 10:36 PM
#71
Just to throw something else into the discussion: ball diffs are still a popular option in off-road for low grip (i.e. dirt) tracks, even in these here brushless days. 
03-29-2022, 08:06 AM
#72
Don't tell that to Team Associated designers when they made the B6.3D with a ball diff. 
Anyways, looks like pricing is out....
Tamiya USA Price versus TowerHobbies Price:
XV-01 Subaru $379 --> $265 Tower
XV-01 Lancia Delta $412 --> $288 Tower
XV-02 Pro $479 --> $335 estimate (0.7 price of list)
Tower discount of $60-70 puts it in the "possible" attainable price of $265-275.
Anyways, looks like pricing is out....
Tamiya USA Price versus TowerHobbies Price:
XV-01 Subaru $379 --> $265 Tower
XV-01 Lancia Delta $412 --> $288 Tower
XV-02 Pro $479 --> $335 estimate (0.7 price of list)
Tower discount of $60-70 puts it in the "possible" attainable price of $265-275.
04-02-2022, 01:00 AM
#75
Yes, ball diffs do have kind of a built-in slipper clutch, but that's only a desirable feature on a car that doesn't already have a proper slipper clutch. The XV-02 will have a proper slipper clutch, at least as an option.
No they don't. Ball diffs provide the same resistance to diffing-out regardless of load or speed, because the resistance is provided by rolling friction between the balls and the thrust washers, and depends exclusively on how tight the thrust assembly is. There is no buildup of resistance as load or speed increases. You can test this easily yourself by sticking a ball diff between two screwdrivers, preloading the ring gear with your fingers as if you were testing for slip, and then rotating one of the outdrives while maintaining the load on the ring gear. There will be no difference in resistance.
Not to mention, ball diffs cannot physically be tightened enough to provide more resistance than the thinnest gear oils, so if you want more than a minimal amount of resistance a gear diff is your only option.