Wednesday, March 5, 2014

GP video

Made a new Ground Pounder video .

Tuesday, March 4, 2014

Fixing the stiction on Redcat Racing's Ground Pounder shocks

  • Stiction

  • Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact. The term is a portmanteau of the term "static friction", perhaps also influenced by the verb "stick".Wikipedia

  • The stock shocks on the Ground Pounder have seem to have issues out of the box with shocks wanting to stay in one position instead of reacting to forces that should make them expand and contract . The severity of this issue seems to very greatly as my step fathers truck shows hints of it but my rear shocks where down right horrible .

  • So what is the fix for this . Some people buy new shocks from other brands such as HPI . Others fix the stock ones . 

  • I elected to Fix the stock ones so here is what I did .

  • Depending on the condition of your shocks your's may require more or less work than mine did my rear shocks where the worst and took 2 hours to do both . My front shocks took ruffly 1 hour .  

  • Remove the shocks from the model . Always rebuild / maintain your shocks in front or rear pairs so they preform equally
  • Remove the spring and lower and upper spring retainers.
  • Remove the upper cap and drain fluid in a clean container if you plan to reuse. Buying a bottle of fresh shock oil in the 20-30 wt rang is recommenced to insure you have enough to fill the shocks completely.
  • Remove the lower eyelet / ball link . Use pliers with a padded jaw or protect the shaft with a soft material if using normal pliers to prevent the shaft from becoming scored .
  • Slide the shock shaft out of the body and then remove the lower cap from the shock . There will be two seals in the body under the lower cap as shown in the picture . Set the smaller thinner o-ring / seal to the side as it will not be used during reassembly.
  • The inclusion of the small o-ring and the hole in the lower cap being undersized is the cause of the sticking in many of these shocks . 
  • Many people drill hole out to a larger size . Since it helps keep the shaft running parallel in the bore of the shock body I elected to use rubbing compound to increase the clearances but still keep slop at bay.

  • Just add a little bit and work it up and down the shaft .
  • After a while the compound will became gray- black wipe the shaft down test fit the cap on the shaft it should be just loose enough that it will slide down the shaft  by just gravity. 
  • Next clean the shaft up with polishing compound it will remove most if not all scratches on the shaft .
  • Apply just a bit 
  • Polish till it shines. 

  • Now reassemble for a test fit .

  • Insert the large o-ring back in the housing covered in plenty of silicone based grease.

  • lubricate the shaft with silicone grease and slide it though the body and the seal install the lower cap and tighten a few threads at a time while working the shaft back and forth to allow the seal to seat . When cap is snug move shaft through its full motion . If it moves  smoothly refill the shock with oil bleed out the air , re-install the upper cap lower eyelet , spring and the spring retainers .

  • If everything isn't silky smooth :

  • First loosen the lower cap a bit and see if the ruff spot is now in a different spot if so the hole in the lower cap is probably of center a bit and the drill bit method might be the best way to go .

  • If there is no change by loosening the lower cap inspect the shock piston it may have a bit of flash not removed at the factory . Light sand the outer diameter and retest .

  • If your still having problems there may be a flaw with the shock bodies bore it's self .

  • Role up a small piece of sand paper and rotate it in the bore . Start with a large grit piece and work down to a fine grit like 1000 . Do another test fit if you feel a improvement move on to using rubbing compound and then polishing compound . Test fit once more when the bore is nicely polished .