Being the typical impatient racer most of us are, I decided to take having a Caster sct into my own hands. It is finally complete and I used it to win the opening race of the Factory Tracks Midwest Series this past Saturday.
With the ex1.5r coming in at 310mm wide on the spec sheet (and confirmed within a mm by measuring at the widest point with blank rims installed) a good 14mm must be removed to be roar legal. I went ahead and narrowed each side by 7mm by having new holes drilled in the rear arms at the hub and the excess arm and old holes cut off. The front arms were even easier, just lopping off the ends and taking a drill bit to the pivot ball holes and boring them a good 6-8mm deeper. It looks completely legit to boot.
For the CVDs, I had an older set from a prior ex1.5r that were 3-4mm shorter than the current ones installed all around and everything is kosher. They are literally .5mm from bottoming out in the diff outdrives throughout most of the suspension range, but hey, it works! With DE Racing sc8 rims and arms level, the track width is down to 295 with blank no tires mounted in the rear and in the front I can screw in the pivot balls to go as narrow as 295 before the cvd's bottom out. With tires mounted, the sidewalls pooch out to 297-298, but when going through tech the sidewalls give enough that they don't seem to care. Heck, I've seen a couple Kyosho's or slashes with the wrong rims on them (pushing them to 300+mm make it through. lol.) Either way, it is close enough that when set at racing ride height with the arms a touch below level all around the car just rolls between two posts set at the ROAR limit of 296mm apart.
Parts list:
SC10 4x4 rear bumper
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBATS&P=7
SC10 2wd front bumper
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXCV9&P=7
SC10 4x4 body mounts
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBAPJ&P=7
Tekin Pro4 4600kv motor/RX8
Front shock tower had a couple corners sanded into the top so I wouldn't have to cut up the body mount and countersunk washers were used so the plastic captured by the shock mounts didn't deform too much. On the rear I was able to trim some plastic from the center of the body mounts rather than grinding the shock tower, but it weakens the mounts and I'll probably buy another set and just grind on the tower a mite. The outermost two holes on the tower and sc10 body mount line up perfectly.
For the front and rear bumpers, holes were drilled in the shock towers just inside of where they mount on the diff case. Plastic nuts were used as spacers for longer screws that went through the towers into the front and rear bumpers. A slight bend in the front skid-plate and boring out the stock holes allows the front two screws that go into the gearbox to capture it nicely. On the rear 3mm threaded holes were made in the 2.5 degree toe block for the rear bumper to mount on.
Ready to race, MINUS body, the car weighs in at 6 lb 10 oz. Current weight savings over my ex1.5r (that weighs 8lb even) come from ditching a pack, smaller motor, no esc tray, carbon fiber front deck/center brace/servo mount, no mud guards, material removed from the stock battery tray, plastic chassis braces, and plastic RC8 spur gear. The bumpers and body mounts perfectly cancel out the weight of the wing mount and wing that were removed.
For tuning I ended up at 35 wt oil and 1.2mm pistons in the front, soft kit springs, outer on the tower and inner on the arm. On the rear I have 25wt oil and 1.2mm pistons, RC8's softest rear spring (black?), second hole from the outside on the tower and outer on the arm, and no swaybar to start. Some limiters were added to the shock shaft to prevent cvd binding in the outdrive at full compression, but the lost travel is minimal. My initial diff oil guesses, that actually felt pretty good on the high traction track, were 7-7-3. Outdoors I might drop to 5-7-2.
Work that still needs to be done or things I would like to change are a custom rear sway bar, titanium turnbuckles for weight, and carbon fiber shock towers. The stock sway bar is way too thick for the lightened car and the mounting locations on the arm are so far out I couldn't find anything in the hobbyshop to work as a substitute. If you watch the video below you'll see I rolled twice, so I need to find some ~1mm music wire (stock bar is 1.8mm) to reduce roll a touch. I also have RCShox.com dual stage pistons on the way.
Here are pics and the youtube video of the main. Don't mind the pink body. It's my wife's and the only one I had on hand that lined up perfectly with the body posts. lol
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With the ex1.5r coming in at 310mm wide on the spec sheet (and confirmed within a mm by measuring at the widest point with blank rims installed) a good 14mm must be removed to be roar legal. I went ahead and narrowed each side by 7mm by having new holes drilled in the rear arms at the hub and the excess arm and old holes cut off. The front arms were even easier, just lopping off the ends and taking a drill bit to the pivot ball holes and boring them a good 6-8mm deeper. It looks completely legit to boot.
For the CVDs, I had an older set from a prior ex1.5r that were 3-4mm shorter than the current ones installed all around and everything is kosher. They are literally .5mm from bottoming out in the diff outdrives throughout most of the suspension range, but hey, it works! With DE Racing sc8 rims and arms level, the track width is down to 295 with blank no tires mounted in the rear and in the front I can screw in the pivot balls to go as narrow as 295 before the cvd's bottom out. With tires mounted, the sidewalls pooch out to 297-298, but when going through tech the sidewalls give enough that they don't seem to care. Heck, I've seen a couple Kyosho's or slashes with the wrong rims on them (pushing them to 300+mm make it through. lol.) Either way, it is close enough that when set at racing ride height with the arms a touch below level all around the car just rolls between two posts set at the ROAR limit of 296mm apart.
Parts list:
SC10 4x4 rear bumper
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBATS&P=7
SC10 2wd front bumper
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXCV9&P=7
SC10 4x4 body mounts
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXBAPJ&P=7
Tekin Pro4 4600kv motor/RX8
Front shock tower had a couple corners sanded into the top so I wouldn't have to cut up the body mount and countersunk washers were used so the plastic captured by the shock mounts didn't deform too much. On the rear I was able to trim some plastic from the center of the body mounts rather than grinding the shock tower, but it weakens the mounts and I'll probably buy another set and just grind on the tower a mite. The outermost two holes on the tower and sc10 body mount line up perfectly.
For the front and rear bumpers, holes were drilled in the shock towers just inside of where they mount on the diff case. Plastic nuts were used as spacers for longer screws that went through the towers into the front and rear bumpers. A slight bend in the front skid-plate and boring out the stock holes allows the front two screws that go into the gearbox to capture it nicely. On the rear 3mm threaded holes were made in the 2.5 degree toe block for the rear bumper to mount on.
Ready to race, MINUS body, the car weighs in at 6 lb 10 oz. Current weight savings over my ex1.5r (that weighs 8lb even) come from ditching a pack, smaller motor, no esc tray, carbon fiber front deck/center brace/servo mount, no mud guards, material removed from the stock battery tray, plastic chassis braces, and plastic RC8 spur gear. The bumpers and body mounts perfectly cancel out the weight of the wing mount and wing that were removed.
For tuning I ended up at 35 wt oil and 1.2mm pistons in the front, soft kit springs, outer on the tower and inner on the arm. On the rear I have 25wt oil and 1.2mm pistons, RC8's softest rear spring (black?), second hole from the outside on the tower and outer on the arm, and no swaybar to start. Some limiters were added to the shock shaft to prevent cvd binding in the outdrive at full compression, but the lost travel is minimal. My initial diff oil guesses, that actually felt pretty good on the high traction track, were 7-7-3. Outdoors I might drop to 5-7-2.
Work that still needs to be done or things I would like to change are a custom rear sway bar, titanium turnbuckles for weight, and carbon fiber shock towers. The stock sway bar is way too thick for the lightened car and the mounting locations on the arm are so far out I couldn't find anything in the hobbyshop to work as a substitute. If you watch the video below you'll see I rolled twice, so I need to find some ~1mm music wire (stock bar is 1.8mm) to reduce roll a touch. I also have RCShox.com dual stage pistons on the way.
Here are pics and the youtube video of the main. Don't mind the pink body. It's my wife's and the only one I had on hand that lined up perfectly with the body posts. lol
