fyrstormer
RCC Addict
My XV-01T Asterion is no more. It was an interesting concept, a pickup truck built on a touring car chassis with rally car suspension, and it worked pretty well, but as time went on I decided its drawbacks (specifically, flagrant traction-rolling in corners) outweighed its novelty. So I converted it into this:
If this body looks familiar, that's because it was originally the body I put on my Tamiya FF-04 Evo last year, minus a few of the more problematic decals:
The irony is not lost on me that my first Tamiya kit was a front-wheel-drive car, my dissatisfaction with which eventually sent me on a months-long quest down the rabbit hole of multiple XV-01 builds, only to end up with my last XV-01 build also being front-wheel-drive.
Yes, my XV-01T has had its drive belt and rear transmission removed, so the rear wheels are just along for the ride, but despite the similarity in drivetrain layout, the XV-01 FF handles very differently from my long-gone FF-04.
The first and most obvious difference from the FF-04 is the suspension; whereas the FF-04 had 55mm TRF shocks, the XV-01 FF has shocks cobbled together from a variety of parts -- TRF pistons, upper and lower caps (limited-edition black parts, no less!), and shaft seals; springs and shafts from the long-damper spec CVA plastic shocks; and longer shock bodies from the Yeah Racing 60mm shock kit. All put together, the difference in shock length is significant:
That extra suspension travel, combined with the XV-01's suspension design, gives the XV-01 FF a LOT more ground clearance, and more ability to keep the front wheels planted when leaning in corners.
Another significant difference between the FF-04 and the XV-01 FF, which can't be seen from the outside, is that the differential has been replaced by a spool. My experience with the FF-04 taught me that traction is desperately limited on a front-wheel-drive RC car, and I decided that faster tire wear was an acceptable tradeoff to ensure that the front wheels would always be able to put power to the ground. If I had the FF-04 to build over again, I'd have replaced the diff with a spool straightaway and not give it a second thought. I think all FWD RCs should have spools; it really does help that much. (there might be an exception for FWD RCs driven on perfectly clean tracks, but not for any others.)
The third important difference between the FF-04 and the XV-01 FF, another thing I learned from experience, is the gearing. The FF-04 comes with 26/68 Mod 0.6 gearing, which translates to 29/77 gearing in 48 pitch. I have no idea what Tamiya was thinking when they equipped a FWD car with gearing that low -- the amount of wheelspin on that car, even with the best tires I could find on warm dry blacktop, was frankly atrocious. The XV-01 FF, on the other hand, is running 38/69 48p gearing with the aid of a Team Associated spur gear -- 46% higher than the FF-04's gearing -- so it can run a higher-turn, lower-power motor without being dog-slow. Whereas my other XV-01s run 12-turn modified brushed motors or 3930KV brushless motors, the XV-01 FF is running a Holmes Hobbies 27-turn disposable motor. (Holmes Hobbies' disposable motors have ball-bearings installed on the pinion side so they doesn't waste power scrubbing the spindle against a bushing, and it will last longer before wearing out.) The slower motor combined with the higher gearing work together to significantly limit torque to the front wheels. 38t is the largest 48p pinion gear that will fit under the gear cover without shaving the tips of the gear teeth (not worth the effort for a non-racing application), though I could go with a smaller spur gear (possibly as low as 65t) if I were willing to ditch the slipper clutch and bolt the sput gear directly to the input shaft. If I had the FF-04 to build over again, I'd definitely do that, but for the purposes of running off-road I definitely want to keep the slipper clutch -- plus the slipper clutch gives me another way to limit torque to the front wheels.
As previously mentioned, the rear gearbox is hollowed-out and empty, the wind whistling forlornly through its vacant interior as the car whizzes down the road -- but the side effect of this is a significant weight reduction as there are no ball-bearings, axles, gears, or outdrives in the back anymore, and most of those parts were steel. So the rear suspension is using the softest long-damper springs Tamiya offers, and 20wt oil in the rear shocks, whereas my other XV-01s require stiffer springs and 30wt oil in the rear. (except for the XV-01 R, which has the motor in the back and thus has even stiffer rear suspension than the rest.)
However, despite the lightened load in the back, there's still a swaybar in the rear, in fact the stiffest of the three swaybars in the XV-01 swaybar kit, whereas the front swaybar is the softest of the three. This chassis absolutely needs swaybars to prevent ridiculous body-roll with all of that suspension travel, but why the imbalance between front and rear? One word: Powerslides. This front-wheel drive car oversteers beautifully; while it can't carry a powerslide as long as a RWD or 4WD car can, it can still get sideways with ease, which makes sharp corners fun. The tires hate me for it, but I don't care.
So there you have it, my Tamiya touring car collection has come full-circle, from building a FWD touring car and not liking it, cannibalizing it to build a 4WD rally car, building several more cars of various configurations on the same platform, and ultimately ending up converting one of them back to FWD and applying the lessons I learned along the way. This one I think I'll keep.
If this body looks familiar, that's because it was originally the body I put on my Tamiya FF-04 Evo last year, minus a few of the more problematic decals:
The irony is not lost on me that my first Tamiya kit was a front-wheel-drive car, my dissatisfaction with which eventually sent me on a months-long quest down the rabbit hole of multiple XV-01 builds, only to end up with my last XV-01 build also being front-wheel-drive.
Yes, my XV-01T has had its drive belt and rear transmission removed, so the rear wheels are just along for the ride, but despite the similarity in drivetrain layout, the XV-01 FF handles very differently from my long-gone FF-04.
The first and most obvious difference from the FF-04 is the suspension; whereas the FF-04 had 55mm TRF shocks, the XV-01 FF has shocks cobbled together from a variety of parts -- TRF pistons, upper and lower caps (limited-edition black parts, no less!), and shaft seals; springs and shafts from the long-damper spec CVA plastic shocks; and longer shock bodies from the Yeah Racing 60mm shock kit. All put together, the difference in shock length is significant:
That extra suspension travel, combined with the XV-01's suspension design, gives the XV-01 FF a LOT more ground clearance, and more ability to keep the front wheels planted when leaning in corners.
Another significant difference between the FF-04 and the XV-01 FF, which can't be seen from the outside, is that the differential has been replaced by a spool. My experience with the FF-04 taught me that traction is desperately limited on a front-wheel-drive RC car, and I decided that faster tire wear was an acceptable tradeoff to ensure that the front wheels would always be able to put power to the ground. If I had the FF-04 to build over again, I'd have replaced the diff with a spool straightaway and not give it a second thought. I think all FWD RCs should have spools; it really does help that much. (there might be an exception for FWD RCs driven on perfectly clean tracks, but not for any others.)
The third important difference between the FF-04 and the XV-01 FF, another thing I learned from experience, is the gearing. The FF-04 comes with 26/68 Mod 0.6 gearing, which translates to 29/77 gearing in 48 pitch. I have no idea what Tamiya was thinking when they equipped a FWD car with gearing that low -- the amount of wheelspin on that car, even with the best tires I could find on warm dry blacktop, was frankly atrocious. The XV-01 FF, on the other hand, is running 38/69 48p gearing with the aid of a Team Associated spur gear -- 46% higher than the FF-04's gearing -- so it can run a higher-turn, lower-power motor without being dog-slow. Whereas my other XV-01s run 12-turn modified brushed motors or 3930KV brushless motors, the XV-01 FF is running a Holmes Hobbies 27-turn disposable motor. (Holmes Hobbies' disposable motors have ball-bearings installed on the pinion side so they doesn't waste power scrubbing the spindle against a bushing, and it will last longer before wearing out.) The slower motor combined with the higher gearing work together to significantly limit torque to the front wheels. 38t is the largest 48p pinion gear that will fit under the gear cover without shaving the tips of the gear teeth (not worth the effort for a non-racing application), though I could go with a smaller spur gear (possibly as low as 65t) if I were willing to ditch the slipper clutch and bolt the sput gear directly to the input shaft. If I had the FF-04 to build over again, I'd definitely do that, but for the purposes of running off-road I definitely want to keep the slipper clutch -- plus the slipper clutch gives me another way to limit torque to the front wheels.
As previously mentioned, the rear gearbox is hollowed-out and empty, the wind whistling forlornly through its vacant interior as the car whizzes down the road -- but the side effect of this is a significant weight reduction as there are no ball-bearings, axles, gears, or outdrives in the back anymore, and most of those parts were steel. So the rear suspension is using the softest long-damper springs Tamiya offers, and 20wt oil in the rear shocks, whereas my other XV-01s require stiffer springs and 30wt oil in the rear. (except for the XV-01 R, which has the motor in the back and thus has even stiffer rear suspension than the rest.)
However, despite the lightened load in the back, there's still a swaybar in the rear, in fact the stiffest of the three swaybars in the XV-01 swaybar kit, whereas the front swaybar is the softest of the three. This chassis absolutely needs swaybars to prevent ridiculous body-roll with all of that suspension travel, but why the imbalance between front and rear? One word: Powerslides. This front-wheel drive car oversteers beautifully; while it can't carry a powerslide as long as a RWD or 4WD car can, it can still get sideways with ease, which makes sharp corners fun. The tires hate me for it, but I don't care.
So there you have it, my Tamiya touring car collection has come full-circle, from building a FWD touring car and not liking it, cannibalizing it to build a 4WD rally car, building several more cars of various configurations on the same platform, and ultimately ending up converting one of them back to FWD and applying the lessons I learned along the way. This one I think I'll keep.
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