My 10T SC conversion

[Maxray]

Really sweet conversion! Well done.

[cautrell05]

Ok the last two weeks have been down to the tedious little details that take forever but at least its finally ready for the track. Almost. I screwed up and told my sticker guy the wrong number of sets so he has to make some more but stickers or not its going to the track tomorrow.




I should have called the project heavy metal. The darn thing seems to gain weight faster than me around the holidays. Oh well. weight ready for the track is 78.5 ounces with 62.3% of that on the rear. I figure i will run this one at least this year and then maybe look into a lighter version 2.

Nick

[slotcarrod]

Very neat conversion and it looks great! Make sure you let us know how it runs!

I was thinking you could move the servo to the front in a parallel position, much like the B2-B4 to give the front a bit more traction with out adding weight!

[soniccj5]

Looks great!! I hope they don't try to prevent you from running the the SC class.

[atarit3]

hmmm, toasty!

[cautrell05]

Well I would love to say that its first day at the track was great and that it was on rails and I could do no wrong with it but lets be realistic. its been close to 10 years sinse I have driven on a track and its basically a new truck with an unproven setup. It didnt go as well as I had hoped but about what I expected. Speed and handling were pretty good when the driver wasnt screwing it up(which happened alot). Definatley drives different from when it was a stadium truck. Kinda pushy on real tight slow corners and too much steering down the straits. I have decided im going to run a couple more packs through it as it sits before I change much. Cant really blame the setup too much when the drivers out of practice. it did help me find a couple of weak points though. Races rained out yesterday and i will be camping in two weeks so it looks like I have another month to fix the little details. Im going to be real tempted to drive to omaha before then just to get some racing in.

Nick

[soniccj5]

I know when I first drove my box stock RTR SC10 it/I was horrible. I was a moving obstacle! I bought a new set of tries for the rear to get better grip on the clay track, then a new batter brace to allow my LiPo the ability to be moved around. Next time I went to the track I was able to be less of an obstacle.

I am sure once you work out the kinks, that thing will fly, and will leave everyone scratching their heads trying to figure out who makes it.

ED

[cautrell05]

Right now it has the kit RTR sc10 tires on it just because I got a new set from ebay for $25. I knew from the get go that they would probably get changed out but I had to get something to start with first. Before I buy any other tires I need to try some different wheels on the back to get some more width. With the wide gt axles on the front it comes out at 11.5 exactly. The rear is only 11 inches though. I have a few ideas but need to see them in person to see for sure how they will work.

My original plan had the lipos held in with the standard rc10 battery cups and some front to rear adjustment. That plan fell through and I was stuck with one place for the batteries. Worse case I will just do what I do on my stock car. hang weight. A half ounce on the front or rear bumper will have more affect on percentages than moving the battery 3/4 of an inch. In the back on my mind I was planning from the getgo for this to be and experiment of sorts and am already thinking of possibly building a second version. For right now it will work.

Nick

[cautrell05]

Well its raining again and everything outside is a muddy mess. Suppose I should get something done on this thing.
After the first, and so far only, day at the track heres how it sat.



No those arent the new 45 degree caster blocks. Too many shots to the wall at the end of the straight with 20 year old caster blocks.



Currently the only caster blocks for the old style front ends still available are the 30 degrees. The ones on there were 20. Figure i will try it with the 30s and see how it feels. I will probably switch it over to the t4/sc10 caster blocks just for the fact that they are easier to get. 20 degree blocks are going for $9 a pair on ebay. Not super high but a bit much for a runner.

Found a few weak points while over there. First lap I missed the crossover and ran head on into one of the pipes. Everything was still in one piece but the steering was way off to the left. I thought maybe it was something in the servo but it still worked ok. Cranked the trim to the right and everything seemed fine. Got home and found out that the upper deck and started to fold at the rear mounts. The change in distance there between the servo and linkage was what made it shift to the left. Looking at it now I can see why it bent. I underestimated how much force went through that plate.



Version 2 is slightly heavier and not as pretty but should be much stronger.



The rear bulkhead brace also started to fold. Didnt think about the force on the rear bulkhead when the rear bumper hits the dirt after a bad landing.



I couldnt think of a good solution there other than just make it stiffer. I simply doubled it up for now. It was only .035 to begin with.

Cant have a short course truck without nerf bars.




Not bad for a big ziptie, a candle and a half hour while watching tv. They should work.
Still need to get back over for some more practice. It has been raining way too much latley but hopefully it will clear off before long.

Nick

[cautrell05]

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

[cautrell05]

More updates. The last weekend went pretty good. Ran 3 heats and the b-main without loosing a tierod so that by itself is progress. Still need to work on crashing less but the truck is pretty good when the driver is doing his job. The heats all went pretty well with lap times at 27.4 pretty consistently. General feeling after the heats is I need more steering on power. tweaking camber and changing springs hasnt made much difference so just to see what happens I strapped 3/4 ounce of lead on the front bulkhead. That made a drastic difference for the better. The front end held beter all the way around both on the sweeper and on the infield. Lap times dropped down to 26.5. When I got home it was time to see how I could shift some weight forward. When I built the truck I was under the impression that midmotors are at a disadvantage because of less rear weight so I built it with everything as far back as possible to keep the rear weight up. all said and done with the club transponder mounted behind the front shock tower it came in at 61.6 rear. With the 3/4 ounce on the front bulkhead it dropped down to 60.9. Because of the way the chassis is laid out there really isnt anything I can move to shift weight forward. Time for a remodel.

This was the first version-



And version 1.1-



No real drastic chages but enough that the servo and left saddle pack are moved as far forward as this chassis will allow. The right side now has about 1 1/2" that it can move forward and back. I also trimmed the front top deck to take a little weight out and make it look better. I also moved the transponder mount to the front of the tower to help shift weight forward some more. Out back I pretty much tore the whole back end down to the chassis. The rear of the chassis that used to attach to the motor plate got trimmed, also for weight. Its not much but every little bit adds up.



I also underestimated how much the suspension would wear. When I put it together it was a little snug both on the chassis mounts and at the rear hubs. After several race days I figured by now it would have freed up by now. Boy was I wrong. With the tires and shocks off the rear suspension would stay in place wherever it was put. Little time with some sandpaper adjusting the spacers on both the inners and outers and it now falls freely. Not that I need more rear traction but it cant hurt.

With everything back together and on the scales it came out to 60.2 rear with the battery back and 59.7 with it to the front. Its not a drastic difference but it should help.



I broke down last week and bought a set of scales off of ebay for $28. Not because I think im good enough to need it but because with handmade front and rear towers I suspect that my corner weights may not be as close as they should.
The truck comes out at 49.8 left side weight which is close enough to balanced im not messing with it. It did however come in 40 grams heavy on the left rear. Not suprising. an extra 1/8" shim under the right rear spring and it came out within 10 grams left and right. Close enough for dirt.
Winters coming and there is a 24"x24" sheet of .080 6061 sitting under my bench that may verywell become version 2. My only complaints with this one is its a little heavy and theres not much room in the chassis to move things around. The next race is this coming sunday and im looking forward to seeing how much it helped.
Nick

[cautrell05]

Time for a quick update. The truck is currently half apart in the garage getting a rework of the front end. The changes to the battery and servo location made a slight improvement. Most of the places I could make up time on other guys were the momentum areas, It seemed to be happier the deeper I drove it in the corner. The front tires are pretty much wore out so that couldnt have been helping but for the last race it was handling as well as I could want. If I could get more consistent with my driving I would be in good shape. Qualified 2nd in the A with my best heat so far this year and If I remember right it had the second fastest lap of the day in qualifying. I had a few stupid moments and ended up 4th but for a homemade truck I couldnt be much happier. Couple of things to adress over the winter.

1. The front tires are worn out. I dont like the front and rear wheel setup so its getting blitz hubs up front so I can run the same wheels as the back.

2. Different battery. I didnt think about it at the first of the year because I didnt know much about lipos in cars and never gave it a second thought after that but the saddle pack in the truck was only a 25c 4800 pack. The fast guy s at the track are geared around 7.50. Whenever I tried to run that high it felt real sluggish in the infield and the motor got pretty warm. I tried more timing and less timing and different gearing but finally ended up with 45 degrees on the endbell, 0 boost, and an 8.00 final. Originally I thought it was the motor or the fact that the truck was heavy, It was 80 ounces. Now Im thinking it was just not enough battery c-rating to get the punch it needed. Solution for that, Losi short packs. Picked up two from th BST section here. Im really looking forward to trying it out and see the difference.

3. rebuid the front end. The Pipe just to the right of the crossover jump was not nice to me at all this year. I noticed that the front bumper used to have a gap between it and the front of the body but as the year went on the gap got smaller till it was stuffed in the grille.

Found the problem.


Its kinda hard to tell but the shock tower is supposed to be 90 degrees from the arms. The top of the shock mounts are almost 3/4 inch to the front in that pic.

Farther in things were not much better.


The old tower was made of two pieces with an L bent at the bottom. The back one was broke off all together and the front was cracked half way through. That got addressed with the new bulkhead.

I have plenty of pics of the rework for next time. Right now its 30 min past midnight and I need to get to bed. One last thing.

This was without a doubt one of the coolest things i have gotten in the mail in a while.


Page 26. Its a small pic and the ride of the month was cooler but hey, its in there.

Nick

[THEYTOOKMYTHUMB]

Congrats! Nice Work!

[soniccj5]

Must feel good to beat the new technology with something you created.

As for the shorty LiPo pack, I am assuming you got the 60C 3800 pack, that will really give your truck some kick. I bought one and could not be happier. Even going from 40C to 60C I can tell a difference.

[cautrell05]

Your right. Theres something deeply satisfying about running a homebuilt car against store bought ones and being competitive. I built my stock car from the bare frame in a friends shop a few years back and although I may not dominate when I show up, Everyone that knows me also knows I will be running near the front. I probably only have $7000 in that car spread out over 8 years and it will run right next to cars that have $20,000 dumped in them. I think it pisses them off. And it makes me smile alot lol.

I dont think anyone has been upset at running against my truck but I know several were really suprised when they saw it run. Its the little things that make you smile.

Im really anxous to see the difference the battery makes. I just wish I would have thought of it sooner.
The region 8 races were a while ago and while i was there watching I decided to get it ready for the novak special coming up in january. I would really prefer to run it in the 17.5 class over mod partially because Im still not that great of a driver, but mainly because Im a bit worried about the original 20 year old stealth tranny. It was designed for buggies back in the early 90s. They never intended for it to be in a 5 pound truck with a brushless motor. so far it has held up pretty good with the 17.5 other than its hard to keep it tight enough not to slip. With mod motor I have my doubts on its lifespan. I do have a complete SC10 gear diff tranny sitting on the bench in the garage ($28 shipped from the bay I couldnt pass it up) However to do it right, it would take a lot of refitting to switch it over. Dont really want to go that far with this truck. The new chassis will get the 4th gen tranny.

Enough boring stuff. On to the pics-



Theres the new .080 6061 upper deck and bulkhead. The bulkhead fixed several of the issues I had with the earlier one. The hinge pin brace is bolted solid where the V1 didnt have one, The tower is bolted on normal. Much easier to change and the whole thing is a bit stronger than it was. This one was a bit over built and slightly heavy but If Im making a one off part, I only want to do it once. The RPM 10T steering was still on it at the time. That got changed out later. You can also see the ballstuds for the front swaybar.

Forgot to mention when I switched to the blitz hubs it made the front end 10mm too wide. Easier solution would have been to use SC10RS wheels to make it up but they wont work out back. I had to use the blitz/ slash rears to get the rear width up to 11.5. Using different offset hex wheels front and back would defeat the purpose of going to the blitz hubs in the first place.

There was just enough room to move the hinge pins in 5 mm on each side and still clear the mounting screws.
I would have used the AE hex kit but they have no plans of an inline steering block for the floating hubs. That was in an email direct from AE. I like how it drove with the inlines before and with the HPI parts I have the option either way.



The narrow bulkhead did require a few adjustments to work. The camber link was in the outer lower hole on the tower and the inner hole on the caster block. The blitz hubs are slightly taller so I moved the inner mount to the upper row to match and the inside hole on the tower along with the outer hole on the caster block. That kept my upper link the same length as before. I wasnt so lucky on the steering though. Because the steering linkage was wider than the inner pivots, no matter what I did I couldnt get the bump steer back where it was. I tried to cheat and make the center link shorter and pull the two halves closer but it made a mess and ended up with really weird ackerman angles. When they say both sides of the steering linkage need to be parallel they arent kidding. The solution even though I didnt really want to was to make a new bellcrank linkage that fit. This is the best pic I had of it before it was assembled.



If I have it apart I will try to get a better pic.
These were the ones I did for my buggy to give you and idea whats involved.







Over all view of the front with the new steering and the front swaybar installed. I still need to trim the ends of the bar but the basics are there. The rack that the steering links are bolted to will probably be replaced with a piece of aluminum before it hits the track. The plastic was just easy for mock up.



These stupid little blocks took way too long to make for no more than they are.



The two slots are different sized depending on how big the bar is.



I really wish I had that shorty pack at the beginning of the year. It fits so much better than the saddle pack did. I still need to get the battery hold downs and receiver mounted. The front is pretty much done. Out back I need to add a brace from the motor plate to the chassis and rebuild the diff. Again. Im also working on a rear swaybar mount so I have the tuning options. It responds pretty well to the soft springs but the body roll is noticable. As of now it has green rears and on the front shocks are an old set of gold rears. Thats where im at right now. I picked up a set of mounted rebars for the indoor track over the winter. Those are all one piece wheels compared the the beadlocks I had on the back. I was rather suprised at the weight difference though. The rebars and shorty pack are a full 6 ounces lighter than the saddle pack, stock SC10 fronts and beadlock rears. Thats freakin cool. It went from over 80 ounces to being just over 75. If I ran my sons slash body instead of the sc10 body it would actually put me underweigh by an ounce. Trust me I thought about it.
Nick