DowntownScience
Rock Crawler
DowntownScience's "Zero F*cks Given" U4 Bomber budget upgrades
U4RC has become all the rage lately in my area with Auburn Performance Raceway putting together a really nice outdoor track.
I have a couple of SCX10's that I probably could have modified for the 1.9 class, but I wanted a KOH style rig. Definitely not anything I could afford prior to the Axial Bomber.
This Bomber will be setup for U4RC, not crawling. The plan is to keep it as stock and light as possible, only replacing the items that break along the way.
Here is a picture of the way she sits today after a few necessary upgrades.
Upgrade #1: Electronics
I didn't think that the stock electronics and 35T motor were going to net many wins so the first thing to get replaced were the electronics. Plus all my batteries have Traxxas connectors!
In place of the stock electronics I planned for...
Radio: Futaba 4PLS radio and a spare receiver I had for it.
ESC: HobbyWing XERUN 90A Sensored Brushless with external Castle BEC (from my 2wd SC10)
Motor: Either a Trinity Monster HP 17.5T locked or the HobbyWing 13.5T that came with the ESC.
Servo: Ordered a Savox SA1230SG. Didn't have anything in my servo inventory that was going to turn those big 2.2's as quick as I would like.
In addition to the servo I ordered a Hot Racing aluminum motor mount and motor plate because I wanted a solid foundation for my brushless power. I also ordered an aluminum steering link kit as this is another area where the plastic just doesn't give you the results you'd like. The last item I ordered was the Axial optional sway bar. A must have for any U4RC!
Waiting for parts, did some painting:
With the Bomber all tore down waiting on parts I decided I would paint the fuel cell and the battery tray pieces. After looking at a bunch of pictures of the 1:1 Bomber it looked to me like the battery tray should actually be painted to look aluminum since it appeared that the aluminum body panels wrapped around the front in addition to the aluminum firewall.
Here's how those turned out.
And that concludes the "building" part of this thread!
Parts Received:
Received the servo, motor mount, motor plate, steering links, and sway bar. Decided to start with the Trinity Monster HP 17.5T motor. I quickly realized that I needed more power and installed the 13.5T motor. Stock gearing. Much better speed. Hadn't made up my mind on wheels and tires yet, so I installed a set of the Axial Rocksters w/ Axial Rip Saw's that I had laying around. Not sure what kind of foams were installed, but they were single stage open cell.
Initial Impressions:
WOW! This truck is going to be a lot of fun! Incredibly nimble for its size and length. Soaks up everything. Rolls ALOT! Not crazy about the spare tire carrier.
Upgrade #2: Suspension links and differential lockers
Portions of my testing took place in front of my house on asphalt. After running through a few battery packs I began to notice that my truck was no longer launching in a straight line. As I'm driving it I'm thinking the links are buckling under acceleration and/or the locker is starting to go and I'm not getting equal tire rotation out of each side.
It was pretty evident to the naked eye that the links were bending and buckling. I didn't open the differential, just decided that if they weren't dead now, they would be soon!
Ordered a set of American Machine Works (Ebay) aluminum links, Boom Racing trailing arms, and Hot Racing steel lockers.
The trailing arms and lockers installed without any issues. The links didn't quite install as shown in the pictures, but I was able to get them installed without any binding of the drive shafts.
NOTE: Do not use plastic bent rod ends to help with the angles. They will break when jumping and/or landing!
Upgrade #3: Wheels and Tires
The original plan was to remove the stock tires with Acetone and mount them to some plastic GMADE GT02 rims that I thought looked pretty nice.
The first problem I ran into is that the stock tires are ribbed all the way down into the inner bead. The inner and outer beads are also a slightly different diameter than most 2.2 tires. I tried the stock tires on the Axial Rocksters that I had and it still didn't work well because the beadlock rings would have to compress the rubber rib inside of the tire. May have worked out OK, just didn't seem like the proper application.
I tried the Axial Rip Saws with the GMADE GT02 rims. These rims are plastic and use an inner bead. I've never been a fan of the inner bead because you don't really have any control over how tight the bead locks down. That is more in the design of the rim. Rims were fairly cheap for the entire set, so what the heck! These rims didn't lock the tire down tight enough and I was able to pull the bead right out by hand.
Decided I would just stick with the Rocksters and the RipSaw's for now. Really liked the tread on the RipSaw's anyway. Ordered a set of the Crawler Innovations Deuces Wild (Tall) foams because I wanted the tires to be very firm, like the way R/C SCT tires are.
Installed the foams in the tires and set out to test some more. I try to be fairly tough on the truck when testing because I'm trying to simulate race conditions as much as possible and want the truck to be ready to race. I don't want to take it out there and have it break on Lap 1!
Links and lockers definitely made the truck a bit more solid. And when you make something more solid you also expose another weakness!
I destroyed those Rocksters during that training session. When I was done the aluminum hex on the axle had made a good 90 degree rotation within the plastic hex of the wheel.
Looks like I'm going to need aluminum wheels!
Like I said previously I don't really like the inner bead design. I like the bead ring design because I know that as long as I tighten down the ring while the tire is seated in the groove properly it WILL NOT come out. No matter how hard I pull on it! This style of wheel seems to be a dying breed! There are a few smaller manufacturers out there that make some very nice wheels, but in the end they're almost as much as VP. Needed to find something much cheaper.
Xtra Speed 2.2 8 spoke beadlocks to the rescue. Great looking wheel in my opinion. The tire wraps the rims and sits in the bead just perfectly. The supplied hardware is a bit soft so you need to be careful to get each screw threaded a few turns before locking anything down or you run the risk of stripping the threads on the screws.
$21.70 per pair on Amazon!
With the wheels installed I noticed some rubbing of the inner bead hardware with the drag link rod end. To eliminate this rub I installed Team KNK 8 mm hexes (stock hexes are 6 mm). The wheel nut would just barely tighten down past flush with the 8mm thick hexes. I applied blue Loctite to each of the axle shaft threads and also purchased a set of the Traxxas flanged nylon locking nuts to try to ensure that the nuts don't fall off while I'm driving!
Upgrade #4: Suspension
Wasn't a giant fan of how easy the Bomber wanted to roll. Thought about heavier springs and re-filling the stock shocks of course, but then began to read Maslin's thread and saw how he went to a 90mm front and 100 mm rear like most 2WD RC SCT's.
Wasn't ready to buy anything quite yet so I installed a set of the stock Traxxas Slash 2WD shocks I had on hand, with 30WT oil F/R, and with the stock white springs F/R. This was definitely an improvement over the stock setup. The rear worked really well. The front seemed stiff. I couldn't really see the front suspension compressing at all when driving quickly over rocks and other terrain. It would flex in crawling situations, but I needed it to be much softer and quicker to tackle track conditions.
I have become a big fan of the Team Associated SC10B stock shocks in my SCX10's and thought that they'd work out really well in this setup also. Here's why! The diameter of these shocks are slightly less than the stock Traxxas shocks. This would allow for faster damping with smaller diameter pistons. They have aluminum bodies. They have a wide range of spring weights available in kits. The shock retainers snap over the shaft so they can't come off while you're driving. There is a wide range of upgrades for this style of shock. If you're lucky you can get a set of 4 for $20- off eBay. $30- for 4 at the most. These shocks aren't threaded but so what! I find it to be faster and more accurate side to side to just use the plastic collars.
Found a F/R set on eBay for $20-. Ordered a set of the black springs for the front (softest). I had several options for the rear springs on hand. Purchased 15WT oil for the fronts and a set of the pistons so that I could make sure that the front had the fastest piston available. Added FT aluminum shock caps.
Initial Testing:
Front - Much better. Front actually had a small amount of droop when sitting static now.
Rear - Much too soft and fast with 30 WT oil and gold springs. Too soft with blue springs, better with red springs (hardest) but still too fast.
So fast that it actually ripped the shock ball end right off of the shaft after flying off of a few jumps! I could also hear the rear end of the cage smacking the rear axle truss each time it landed. Went to 40 WT oil in the rear to slow it down. With the red springs it is perfect now!
Purchased 100 mm limit straps for the rear to give the shocks a bit of support and to ensure that the ball end doesn't come off again!
Moved the front shocks outside of the shock mounts for greater stability (Thanks Maslin!)
The Bomber is on rails now!
U4RC has become all the rage lately in my area with Auburn Performance Raceway putting together a really nice outdoor track.
I have a couple of SCX10's that I probably could have modified for the 1.9 class, but I wanted a KOH style rig. Definitely not anything I could afford prior to the Axial Bomber.
This Bomber will be setup for U4RC, not crawling. The plan is to keep it as stock and light as possible, only replacing the items that break along the way.
Here is a picture of the way she sits today after a few necessary upgrades.
Upgrade #1: Electronics
I didn't think that the stock electronics and 35T motor were going to net many wins so the first thing to get replaced were the electronics. Plus all my batteries have Traxxas connectors!
In place of the stock electronics I planned for...
Radio: Futaba 4PLS radio and a spare receiver I had for it.
ESC: HobbyWing XERUN 90A Sensored Brushless with external Castle BEC (from my 2wd SC10)
Motor: Either a Trinity Monster HP 17.5T locked or the HobbyWing 13.5T that came with the ESC.
Servo: Ordered a Savox SA1230SG. Didn't have anything in my servo inventory that was going to turn those big 2.2's as quick as I would like.
In addition to the servo I ordered a Hot Racing aluminum motor mount and motor plate because I wanted a solid foundation for my brushless power. I also ordered an aluminum steering link kit as this is another area where the plastic just doesn't give you the results you'd like. The last item I ordered was the Axial optional sway bar. A must have for any U4RC!
Waiting for parts, did some painting:
With the Bomber all tore down waiting on parts I decided I would paint the fuel cell and the battery tray pieces. After looking at a bunch of pictures of the 1:1 Bomber it looked to me like the battery tray should actually be painted to look aluminum since it appeared that the aluminum body panels wrapped around the front in addition to the aluminum firewall.
Here's how those turned out.
And that concludes the "building" part of this thread!
Parts Received:
Received the servo, motor mount, motor plate, steering links, and sway bar. Decided to start with the Trinity Monster HP 17.5T motor. I quickly realized that I needed more power and installed the 13.5T motor. Stock gearing. Much better speed. Hadn't made up my mind on wheels and tires yet, so I installed a set of the Axial Rocksters w/ Axial Rip Saw's that I had laying around. Not sure what kind of foams were installed, but they were single stage open cell.
Initial Impressions:
WOW! This truck is going to be a lot of fun! Incredibly nimble for its size and length. Soaks up everything. Rolls ALOT! Not crazy about the spare tire carrier.
Upgrade #2: Suspension links and differential lockers
Portions of my testing took place in front of my house on asphalt. After running through a few battery packs I began to notice that my truck was no longer launching in a straight line. As I'm driving it I'm thinking the links are buckling under acceleration and/or the locker is starting to go and I'm not getting equal tire rotation out of each side.
It was pretty evident to the naked eye that the links were bending and buckling. I didn't open the differential, just decided that if they weren't dead now, they would be soon!
Ordered a set of American Machine Works (Ebay) aluminum links, Boom Racing trailing arms, and Hot Racing steel lockers.
The trailing arms and lockers installed without any issues. The links didn't quite install as shown in the pictures, but I was able to get them installed without any binding of the drive shafts.
NOTE: Do not use plastic bent rod ends to help with the angles. They will break when jumping and/or landing!
Upgrade #3: Wheels and Tires
The original plan was to remove the stock tires with Acetone and mount them to some plastic GMADE GT02 rims that I thought looked pretty nice.
The first problem I ran into is that the stock tires are ribbed all the way down into the inner bead. The inner and outer beads are also a slightly different diameter than most 2.2 tires. I tried the stock tires on the Axial Rocksters that I had and it still didn't work well because the beadlock rings would have to compress the rubber rib inside of the tire. May have worked out OK, just didn't seem like the proper application.
I tried the Axial Rip Saws with the GMADE GT02 rims. These rims are plastic and use an inner bead. I've never been a fan of the inner bead because you don't really have any control over how tight the bead locks down. That is more in the design of the rim. Rims were fairly cheap for the entire set, so what the heck! These rims didn't lock the tire down tight enough and I was able to pull the bead right out by hand.
Decided I would just stick with the Rocksters and the RipSaw's for now. Really liked the tread on the RipSaw's anyway. Ordered a set of the Crawler Innovations Deuces Wild (Tall) foams because I wanted the tires to be very firm, like the way R/C SCT tires are.
Installed the foams in the tires and set out to test some more. I try to be fairly tough on the truck when testing because I'm trying to simulate race conditions as much as possible and want the truck to be ready to race. I don't want to take it out there and have it break on Lap 1!
Links and lockers definitely made the truck a bit more solid. And when you make something more solid you also expose another weakness!
I destroyed those Rocksters during that training session. When I was done the aluminum hex on the axle had made a good 90 degree rotation within the plastic hex of the wheel.
Looks like I'm going to need aluminum wheels!
Like I said previously I don't really like the inner bead design. I like the bead ring design because I know that as long as I tighten down the ring while the tire is seated in the groove properly it WILL NOT come out. No matter how hard I pull on it! This style of wheel seems to be a dying breed! There are a few smaller manufacturers out there that make some very nice wheels, but in the end they're almost as much as VP. Needed to find something much cheaper.
Xtra Speed 2.2 8 spoke beadlocks to the rescue. Great looking wheel in my opinion. The tire wraps the rims and sits in the bead just perfectly. The supplied hardware is a bit soft so you need to be careful to get each screw threaded a few turns before locking anything down or you run the risk of stripping the threads on the screws.
$21.70 per pair on Amazon!
With the wheels installed I noticed some rubbing of the inner bead hardware with the drag link rod end. To eliminate this rub I installed Team KNK 8 mm hexes (stock hexes are 6 mm). The wheel nut would just barely tighten down past flush with the 8mm thick hexes. I applied blue Loctite to each of the axle shaft threads and also purchased a set of the Traxxas flanged nylon locking nuts to try to ensure that the nuts don't fall off while I'm driving!
Upgrade #4: Suspension
Wasn't a giant fan of how easy the Bomber wanted to roll. Thought about heavier springs and re-filling the stock shocks of course, but then began to read Maslin's thread and saw how he went to a 90mm front and 100 mm rear like most 2WD RC SCT's.
Wasn't ready to buy anything quite yet so I installed a set of the stock Traxxas Slash 2WD shocks I had on hand, with 30WT oil F/R, and with the stock white springs F/R. This was definitely an improvement over the stock setup. The rear worked really well. The front seemed stiff. I couldn't really see the front suspension compressing at all when driving quickly over rocks and other terrain. It would flex in crawling situations, but I needed it to be much softer and quicker to tackle track conditions.
I have become a big fan of the Team Associated SC10B stock shocks in my SCX10's and thought that they'd work out really well in this setup also. Here's why! The diameter of these shocks are slightly less than the stock Traxxas shocks. This would allow for faster damping with smaller diameter pistons. They have aluminum bodies. They have a wide range of spring weights available in kits. The shock retainers snap over the shaft so they can't come off while you're driving. There is a wide range of upgrades for this style of shock. If you're lucky you can get a set of 4 for $20- off eBay. $30- for 4 at the most. These shocks aren't threaded but so what! I find it to be faster and more accurate side to side to just use the plastic collars.
Found a F/R set on eBay for $20-. Ordered a set of the black springs for the front (softest). I had several options for the rear springs on hand. Purchased 15WT oil for the fronts and a set of the pistons so that I could make sure that the front had the fastest piston available. Added FT aluminum shock caps.
Initial Testing:
Front - Much better. Front actually had a small amount of droop when sitting static now.
Rear - Much too soft and fast with 30 WT oil and gold springs. Too soft with blue springs, better with red springs (hardest) but still too fast.
So fast that it actually ripped the shock ball end right off of the shaft after flying off of a few jumps! I could also hear the rear end of the cage smacking the rear axle truss each time it landed. Went to 40 WT oil in the rear to slow it down. With the red springs it is perfect now!
Purchased 100 mm limit straps for the rear to give the shocks a bit of support and to ensure that the ball end doesn't come off again!
Moved the front shocks outside of the shock mounts for greater stability (Thanks Maslin!)
The Bomber is on rails now!
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