Tuesday, October 30, 2012

HPI Cup Racer Front One Way Mods Shopping List

Here's the complete list to mod a TT-01 one way into the HPI Cup Racer. See part1, part2 and part3 for instructions. After running a pack, it's a fragile setup in that the diff gear can wander on the pressed bearing in a bearing jury rig. But, it drives so much better and the looks of the 510 are always great.

Boca Bearing
  • 2x 3x10x15mm bearings
  • 2x 3x6x10mm bearings
  • Bench vice, or similar, to press the bearing into the bearing 
  • (or 2x 3x6x15mm bearing, I couldn't find one)
Eagle Racing
  • TT-01 one way diff unit 
HPI 
  • Cup Racer ball diff bevel gear - use the stock one that's already in the car, you won't need a ball diff for drifting if you lock the gear diff in the rear
 
Dremel bits
  • Grinding stones 
    • 1x small drum grinding stone
    • 1x tapered grinding stone
  • Sanding Disks
  • Drill bit, or small Dremel bit to hog out the ball diff hole

Safety bits
  • Always wear safety goggles and a dust mask/bandana when grinding
  • It's a good idea to wear gloves when using a Dremel (mechanics gloves are great)

Modding the HPI Cup Racer for a Front One Way, part3

Some additional grinding, and the Eagle Racing TT-01 one way fits!


 widen the axle cup openings

The dogbone pins are too thick to fit the drive cups. Use a Dremel sanding disk to slowly remove material. Check often until you have a smooth fit. I ended up with a bit of slop on the pins, and will move to blades when they wear in.




 




Plunge and enlarge the center hole
After the fit is good, a new obstacle presents itself - the dogbone is too wide to fit into the axle cup. Use a tapered or other Dremel grinding stone to enlarge the cup center bore. Again, go slowly and check fit often.










check for binding before install




 nice gear mesh





Check everything for fit  before final assembly. Add a high quality grease to the CVDs to reduce friction and wear.















Sunday, October 21, 2012

Modding the Cup Racer for a Front One Way, part 2

Success! Just a bit of grinding, some bearings and there's a TT-01 one way in your Cup Racer.



I wanted to keep costs relatively low on this project, reusing parts where possible. The stock ball diff bevel gear is a near perfect ringer on the TT-01 one way. Start with the stock diff and use a Dremel to grind down the inner race lip-amajig. Once smoothish, plunge down and enlarge the opening to fit. ~12mm center bore is the goal.



The ball hole seats on the diff need to be hogged out a bit, they're set a hair too far apart. These are what are going to center the diff ultimately, the center hole only need to be mostly round and allow you to get an even fit on the screws. Reuse the three stock screws that came with the one way. Yes, they're phillips head..







Upon test fit, the gear mesh was too loose for my liking. Servicable, but needs work. Grind the diff on mounting ring slightly, you should have a good feel for this by now. I didn't measure, but it's less than 1mm.




Add blue Loctite and re-assemble. Keep one plastic washer on the driver's side (US standard) between the custom bearing and diff cup.

 




 

And that's how to mod a tt-01 one way to a HPI Cup Racer bulkhead. Of course the dog bone pins don't fit the diff cups. Part 3 - Grind the drive cupes.




Click for part1 if you missed it..

Wednesday, October 17, 2012

Modding the Cup Racer for a Front One Way, part 1




I made a bit more progress on the Cup Racer front one way tonight. I couldn't find the right size bearing, even from Boca Bearing. But with a little creative thinking and a bench vice I came up with a bearing inside a bearing.


Start by hand pressing the inner bearing - the tolerances are great, you can get a very smooth seat before pressing it with a clamp.




The Eagle Racing front one way includes two plastic shims, use one for a nearly perfect fit in the bulk head. 







I *think* this is going to line up perfectly - the measurements with my cheapo caliper makes it look good enough for metal gears.


Next step is to drill out the bevel gear center hole to fit the one way.

Click for part2..

Saturday, September 29, 2012

RCRK @inMotion Car Show

It was an epic finish to the summer season - outdoor drifting just 100ft from the long drift sweeper @Monroe Speedway where 1:1 drift cars provided an epic sound track. inMotion claims to be the only indoor car show in Washington... seems about right - it's been years since HIN graced us with their lifestyle event. Admittedly, I've become jaded to car shows over the years - but the metal on display struck a chord and I found many favorites.

After a lengthy sweep session, we setup one of the largest tracks we've ever run. A slight elevation gain as you exit the McDonalds (to the right in the pic), with amply fresh sealed asphalt providing the backdrop. Surface was typical for a fresh, low traffic lot - we were very pleased, having done no pre-Recon. For asphalt surfaces, I default to R2hobbies t-drift clones. These are nowhere near the grip of branded HPI tires, but the price more than makes up for it on a mildly grippy surface.





Saturday, September 22, 2012

RCRK @Desirable Car Show


RCRK hosted the track at the Desirable show at Hotel Murano in Tacoma, Wa. The skies were clear and temps were still up this late September weekend. We didn't expect much from our early recon; painted concrete with mixed sand and rough patches throughout. After a few tries we settled on a layout close to the D1 that hits Monroe Speedway.

Bodies were dragging by the evening as tires wore thin. I preferred R2hobbies High Pressure Cast drift tire for this event. The surface provided gobs of grib, albeit inconsistently, as it shredded through tires due to the sand grit that was embedded in the surface. These tires are very hard, and just don't work for me on asphalt or smoother - but on this surface they gave great speed and control.