WOW, I suck at updates. Sorry guys. Had a few weekends of racing on it now and heres how it went. -
First weekend ran heats only. Had something going on and had to miss the mains. Ran with the stock RTR tires Track was a bit dry and it sucked. No forward bite at all, spun out alot, mainly on entry not so much on exit. Outer steering ends popped off a couple of times. Also noticed that if it came off a jump even slightly nose down the front bumper and chassis would dig dirt hard. every time. Threw the softest springs I had on the back and it helped a little but it still sucked. Got last. Imagine that.
I figured adding some down travel would probably help with the nosedown issue. Theory was that the sooner the tires hit the ground the sooner the shocks could start slowing it down. Sounded good anyway. The front shocks were already in the bottom row of holes on the tower and I wasnt going to dissasemble the front end to drill more holes. I also didnt need the extra travel of the 1.32 shocks but I could make use of the longer bodys. threw a new set of fronts together. 1.32 team shock bodys and 1.02 shafts with 40wt and #2 pistons. Went through and checked camber and found that it was off a bit on 2 corners. Dont remember which but it was a pain to set. Camber changes alot with ride height and it would never sit at the exact same height. Got it set pretty close and ran it.
New tires and rims for the back.
Proline beadlocks and Bowfighters. huge improvement as expected over the old ones. Also pushed the rear out from 11 inches wide to 11 5/8. In practice it felt much better. No problems with traction and the longer shocks seemed to handle the nosedown landings without bottoming out. Racing though was a different story.
First heat lost outer ball cup again.
Second heat wheel nut came loose last lap. rounded out the hex and just about ruined the wheel. CA'd a new hex in the wheel and ran it the rest of the day.
Third heat lost another outer cup. I thought for sure it was because I was running 1/8 of bumpsteer spacers under the outer ballstud on the fairly flexible old style RC10 arms and under a hard shot(there were plenty) it would simply flex over and pop off. For the main I pulled the spacers off of both sides and ran it that way and hoped for the best.
Also noticed several times over the day that on landings if it was leaning at all the outside tire would catch and send it end over end diagonaly. 3 laps into the main it cartwheeled again and the rf arm flexed back(RPM) enough that the shock body hit the tower and bent the shaft. Ran it for 2 laps with the shock locked up and pulled off. Went home pretty discouraged.
I did play with front springs over the day. Started the day with the red fronts 3.9# First heat it was a bit pushy going it. Figured id go drastic and see what difference it made so I put the red rears 2.95# on the front. Huge imrpovement both on power and off. Didnt notice any escessive roll or dive in the corners. Third heat went just a bit stiffer and tried the silver fronts 3.22#. Noticably less steering. Went back to the 2.95#s for the main. Once again steering was pretty good. Lap times were 2-3 seconds off from the rest of the field though. Time to regroup.
I sat down the next week and looked the truck over and tried to figure out what I was doing wrong. Besides the obvious of building a custom truck instead of running a kit truck. I started looking at what I was fighting. Then I started over with the setup. First off the excessive front down travel was causing my tuck and roll on landings. Second I forgot about taking the soft rear springs off when I changed tires. Third I had a duh moment on the front springs. Pulled the front shocks off and replaced the #2s with #3s same 40 weight. More pack is supposed to help with the big jumps. Amazing what you find out when you read. Mounted the front shocks in the top row with the arms totally straight at full droop. In the rear I moved the shocks from the middle to the outer holes on the arms and went from the old springs that rated out at 1.7 and threw in a new set of greens 1.9#. Moving the shocks out in back should stiffen it up and take some bite out of it. Im not hurting for traction at all now as it sits.
On the front springs I kinda remembered something that i had forgotten long ago from my stock car. The guys with the stock front ends had a real low roll center and needed to run stiffer springs to keep the car from laying over in the corners. The guys with the higher roll center can get by with softer springs. All of the cars and trucks out there have super low roll centers with no negative camber gain. Mine is the opposite. Front and rear have a fairly high roll center with a very visible camber gain. Im going with the same theory here as I do on my stock car. I dont care where the roll center is. I want the geometry to get the most traction out of the tire as possible.
Got a little side tracked there. The point is with the higher roll center the red fronts that everybody and their neighbor are running was too stiff. Thats why it reacted better to the softer springs.
Last thing I did was change the spindles. It was running the old first gen RC10 caster blocks and steering arms. I was positive that the arms were flexing and thats why the outers kept popping off. Keep in mind 5 pounds is alot more than the cars weighed back when they used those arms. The old steering arms were inline axles and even though everything now used trailing axles I wanted to stick with changing one thing at a time so I went with the sc10 inline axles and caster blocks. I kept the stock 3mm kingpin but reamed the hinge pin out for 1/8. Other than that it was a straight drop in. Bump steer came out fine with no spacers so I was happy.
For the third weekend I went to some 2.6# springs on the front. I also changed how I set up the truck.
For setting camber and toe I have a wide plastic block that sits sideways in back to set the rear chassis height and keep the chassis level side to side and a narrow one in front that sets the height in front. Throw enough weight on it to hold it on the blocks and then I can set camber without guessing. Afterwards I set my spring heights so it sits at the same height on its own. For me it seems more consistent anyway.
I also had to make a front hinge pin brace to see if I can make the front bulkhead last till the end of the season.
I recently figured out how to mill delrin parts at home so a new front bulkhead is in order over the winter. On one hand im kinda dissapointed how sloppy the bulkhead got but considering some of the hits it has taken and how may arms and bulkheads I would have replaced it was worth the money.
Third weekend out. Limited front drop, #3s 40wt 2.6 fronts, outer holes in back arm, 40 wt #1s 1.9 in back.
Holy crap. I could not believe the difference it made. Way more stable, much better steering, less bottoming out. Overall faster and easier to drive. Outer ball cup came off again in practice. So much for the steering arm theory. Before the first heat I put a pair of losi ends on both outers. First heat was up to second and lost a ball cup again. Getting tired of this. Set second fasted lap time for the heat. I went from low 30s the week before to a 27.6 i believe.
Didnt change anything for the second heat. Lap times improved to 27.4. Made it a whole race without breakng. Still crashed too much though.
Tried to fine tune it a little bit for the third heat. It needed just a little more steering in and coming out. (great place for an adjustable battery mount. Darnit) I moved the rear hubs back to the rear position and upped the rear springs from 1.9 to a 2.3. Didnt make it better. All in all it just didnt feel as good. Didnt matter anyway. stupid ball cup came off again. I fixed it this time. Something may break but that thing aint popping off now.
Lower shock mounts. I used one of the pivot balls from my old shocks because it had the spacer made into it but they are the same height as the old ball stud. I also put the green springs back on the rear. I did however put the gray springs on the front. The 2.33 was the next step softer from what was on there already.
B feature started off good. I got off to a huge lead early on and just set in cruise mode. Half way through the shortcourse mains they run a competition caution. Sure enough first corner I cut it too close and get stuck in the board. I made it back up to second but couldnt catch the leader even though I had no problem earlier in the race. I settled for second happy that the truck didnt break and it was finally running fast enough to be competitive. I did find out afterwards that the left rear shock had no oil left in it. My guess is that stupid snap washer came out because it was bone dry before the b-main.
It also felt really good to have several people come up and comment on how much faster it got and how good it looks out there. With a home built truck that means a lot. Thats where its at now. Need to rebuild a shock and clean it off and i think its ready to go again. Looking forward to the next outing.
Nick