BMI's DB12R
#2086
Tech Lord
iTrader: (13)
Thanks for the feedback guys. Here is some more info on how I built my car.
Front End Assembly:
When I setup the car, I took my time to make sure the front end was free but didn't have too much slack. I used a 1/8" drill bit to hand-ream out the steering knuckles. The upper arms were binding against the caster blocks when there was a shim on each side of the block. To correct this, I sanded a shim on each side (the one on the front side of the caster block) until the arm move and fell freely with very little front-to-back slop.
For installing the pivot balls, I don't have the CRC or IRS pivot ball tool, so I used a small hobby vise instead. The jaws on the vise are smooth and I used this to slowly press in the pivot balls making sure they were parallel the entire time. All four pivot balls move freely and don't have any slop in them.
For the steering linkage ball cups, I used the plastic bag trick to remove the slop but made sure I didn't go too far. To test them, I would check for no slop but made sure the linkage would freely fall when only connected to one side of the linkage.
Front End After Driving:
After driving the car for a couple packs and hitting the boards quite a few times, I have noticed additional slop in the front wheels. What I'm referring to is checking the front tires for camber slop when the chassis is lifted up. There is definitely more slop there now than when I first assembled the car. It appears that the steering knuckle is where the problem is but I still need to check for problems with the king pin in the pivot balls and/or any issues with the pivot balls and the arms.
Question: How much movement is acceptable on the front end? Is it ok for the camber to move +/- 1 degree? What about the steering toe? what's acceptable for that movement?
Rear End:
For the axle spacing, I did notice the clamping hub was backwards before I drove the car. I use an Integy setup board and lined up the balancing holes on the chassis with the center line on the setup board. That's where I noticed it when shimming the rear wheels. My car is using four axle shims on each side for the rear to get to 172mm while still keeping the chassis balancing hole centered on the board.
The diff is very smooth and it was difficult to move the spur gear while holding the rear wheels when I assembled the car. After driving the car for a couple packs, the spur gear was then able to move easier when holding the rear wheels so I tightened up the diff about 1/8th of a turn.
Balance:
I'm using an LRP QC2 ESC, a Spectrum Micro receiver, and an AMB PT in the car. With everything installed, including batteries and wiring, the car does balance when left static. I'm using the Hudy balancing pins as I don't have the IRS balancing balls yet. To compensate for any binding of the pin in the chassis hole, I would purposly tip the car to each side and made sure the "fall" point was even both left to right. I'm not sure how valid that test is but I did it anyway.
Tweak:
Before I drove the car, I put the car on a couple different tweak stations. I have a Speedmind bubble tweak station and the tweak was ok. I then used a buddy's Integy laser tweak station and the car was laser was splitting the center line in the middle. I also put it on another buddy's MIP bubble tweak station and it was off a bit. Not drastically, but some.
The reason I checked it on more than one station is because the rear pod isn't flat to the chassis when there is no load on the car. When you pick up the car and inspect the bottom, you can see that the rear pod isn't parallel to the chassis left to right. I haven't measured this difference yet with my calipers but to me, if you can visually see the difference, it's too much. When checking this, I made sure the motor wires weren't binding in any way either. I plan on rebuilding the L-plates to the chassis to see if this corrects it.
I find it strange that I can see the chassis difference but the tweak was ok (for the most part...) on the tweak stations.
Handling Question:
Aside from the specifics of my car, what would you guys do for a car that you can see the inside front tire lifting on high-speed turns? My thought is to stiffen up the side-to-side movement of the rear pod with either thicked dampening fluid and/or a heavier spring, T-plate, L-plate, etc (take your pick based on the chassis type). What do you guys think?
Thanks,
Front End Assembly:
When I setup the car, I took my time to make sure the front end was free but didn't have too much slack. I used a 1/8" drill bit to hand-ream out the steering knuckles. The upper arms were binding against the caster blocks when there was a shim on each side of the block. To correct this, I sanded a shim on each side (the one on the front side of the caster block) until the arm move and fell freely with very little front-to-back slop.
For installing the pivot balls, I don't have the CRC or IRS pivot ball tool, so I used a small hobby vise instead. The jaws on the vise are smooth and I used this to slowly press in the pivot balls making sure they were parallel the entire time. All four pivot balls move freely and don't have any slop in them.
For the steering linkage ball cups, I used the plastic bag trick to remove the slop but made sure I didn't go too far. To test them, I would check for no slop but made sure the linkage would freely fall when only connected to one side of the linkage.
Front End After Driving:
After driving the car for a couple packs and hitting the boards quite a few times, I have noticed additional slop in the front wheels. What I'm referring to is checking the front tires for camber slop when the chassis is lifted up. There is definitely more slop there now than when I first assembled the car. It appears that the steering knuckle is where the problem is but I still need to check for problems with the king pin in the pivot balls and/or any issues with the pivot balls and the arms.
Question: How much movement is acceptable on the front end? Is it ok for the camber to move +/- 1 degree? What about the steering toe? what's acceptable for that movement?
Rear End:
For the axle spacing, I did notice the clamping hub was backwards before I drove the car. I use an Integy setup board and lined up the balancing holes on the chassis with the center line on the setup board. That's where I noticed it when shimming the rear wheels. My car is using four axle shims on each side for the rear to get to 172mm while still keeping the chassis balancing hole centered on the board.
The diff is very smooth and it was difficult to move the spur gear while holding the rear wheels when I assembled the car. After driving the car for a couple packs, the spur gear was then able to move easier when holding the rear wheels so I tightened up the diff about 1/8th of a turn.
Balance:
I'm using an LRP QC2 ESC, a Spectrum Micro receiver, and an AMB PT in the car. With everything installed, including batteries and wiring, the car does balance when left static. I'm using the Hudy balancing pins as I don't have the IRS balancing balls yet. To compensate for any binding of the pin in the chassis hole, I would purposly tip the car to each side and made sure the "fall" point was even both left to right. I'm not sure how valid that test is but I did it anyway.
Tweak:
Before I drove the car, I put the car on a couple different tweak stations. I have a Speedmind bubble tweak station and the tweak was ok. I then used a buddy's Integy laser tweak station and the car was laser was splitting the center line in the middle. I also put it on another buddy's MIP bubble tweak station and it was off a bit. Not drastically, but some.
The reason I checked it on more than one station is because the rear pod isn't flat to the chassis when there is no load on the car. When you pick up the car and inspect the bottom, you can see that the rear pod isn't parallel to the chassis left to right. I haven't measured this difference yet with my calipers but to me, if you can visually see the difference, it's too much. When checking this, I made sure the motor wires weren't binding in any way either. I plan on rebuilding the L-plates to the chassis to see if this corrects it.
I find it strange that I can see the chassis difference but the tweak was ok (for the most part...) on the tweak stations.
Handling Question:
Aside from the specifics of my car, what would you guys do for a car that you can see the inside front tire lifting on high-speed turns? My thought is to stiffen up the side-to-side movement of the rear pod with either thicked dampening fluid and/or a heavier spring, T-plate, L-plate, etc (take your pick based on the chassis type). What do you guys think?
Thanks,
It is hard to say what the problem is buddy. I will need to see the car. I have not heard anything like this in any of the kits. If you would like to send the car to me to check out i can get things figured out. It is hard to say what the problem is without seeing it. Let me know and i will get it done quickly for you
#2087
Tech Elite
iTrader: (16)
I just wanted to get on the record saying that Jason has built and assembled a very fine race car worth every penny. My first impression opening the kit was: here's a guy that has put every cool & practical part need into a kit. I built the kit per the instruction minus the recommended 35wt center shock oil using 30 instead for our bumpy track. I glued the servo down instead of using the mounts (late night and it didn't have ears). Put a Speed 8 on top of it, a 19t in it. The Jaco Lilac/yellow combo was very good. The car has a great dispossition on the track. It's very fast right out of the wrapper.
Bravo!
Brian; Slapmaster Tools
Bravo!
Brian; Slapmaster Tools
#2090
Tech Fanatic
Thanks for the feedback guys. Here is some more info on how I built my car.
Handling Question:
Aside from the specifics of my car, what would you guys do for a car that you can see the inside front tire lifting on high-speed turns? My thought is to stiffen up the side-to-side movement of the rear pod with either thicked dampening fluid and/or a heavier spring, T-plate, L-plate, etc (take your pick based on the chassis type). What do you guys think?
Thanks,
Handling Question:
Aside from the specifics of my car, what would you guys do for a car that you can see the inside front tire lifting on high-speed turns? My thought is to stiffen up the side-to-side movement of the rear pod with either thicked dampening fluid and/or a heavier spring, T-plate, L-plate, etc (take your pick based on the chassis type). What do you guys think?
Thanks,
If you don't have enough steering, fix that - camber, castor, T-bar, L-bar, centre spring, whatever - but simply increasing the damping doesn't work for me.
When measuring the axle width to be central to the chassis, use the stand-offs on the side of the car; those supporting the cross brace, or the body post/side damper plates on the DB12R. Place a steel rule against the post at 90deg to the chassis, then place a straight edge (or another ruler) along the edge of the wheels. Read off the dimension, repeat for the other side. This is far more accurate than trying to find the middle of the chassis, and reading from a mark on the car. HTH
#2091
I'd go softer on the back, especially the damping. Increasing the side damping always seems to me to give good initial steering, but then the car doesn't straighten up on the exit, and I have to hold off the throttle until it points the way I want to go. Less side damping might give more initial steering, but hurts the rest of the turn.
If you don't have enough steering, fix that - camber, castor, T-bar, L-bar, centre spring, whatever - but simply increasing the damping doesn't work for me.
When measuring the axle width to be central to the chassis, use the stand-offs on the side of the car; those supporting the cross brace, or the body post/side damper plates on the DB12R. Place a steel rule against the post at 90deg to the chassis, then place a straight edge (or another ruler) along the edge of the wheels. Read off the dimension, repeat for the other side. This is far more accurate than trying to find the middle of the chassis, and reading from a mark on the car. HTH
If you don't have enough steering, fix that - camber, castor, T-bar, L-bar, centre spring, whatever - but simply increasing the damping doesn't work for me.
When measuring the axle width to be central to the chassis, use the stand-offs on the side of the car; those supporting the cross brace, or the body post/side damper plates on the DB12R. Place a steel rule against the post at 90deg to the chassis, then place a straight edge (or another ruler) along the edge of the wheels. Read off the dimension, repeat for the other side. This is far more accurate than trying to find the middle of the chassis, and reading from a mark on the car. HTH
#2093
It is hard to say what the problem is buddy. I will need to see the car. I have not heard anything like this in any of the kits. If you would like to send the car to me to check out i can get things figured out. It is hard to say what the problem is without seeing it. Let me know and i will get it done quickly for you
#2095
R/C Tech Elite Member
iTrader: (101)
Jason, Nice talking with you on the phone, The car is on its way, i sent it to your shop.
In response to my question earlier why my car wasnt handling, I put it together exactly how the manual says, The step where it tells you how to put the clamping hub carrier on, it says shallow end towards the rim.. Its supose to be deep end towards the rim. This is my first time runnign 12th, I didnt think i had to check the left to right rear wheel distance cause i put it together per manual. Jason said he is going to get the manual revise to fix that and some other things.
Thus, my car was spinning one way cause one side was longer, thus my tweek was way off!
In response to my question earlier why my car wasnt handling, I put it together exactly how the manual says, The step where it tells you how to put the clamping hub carrier on, it says shallow end towards the rim.. Its supose to be deep end towards the rim. This is my first time runnign 12th, I didnt think i had to check the left to right rear wheel distance cause i put it together per manual. Jason said he is going to get the manual revise to fix that and some other things.
Thus, my car was spinning one way cause one side was longer, thus my tweek was way off!
#2099
Chemical X - maybe I missed it, but I had a few questions:
1) What size tires are you running front and rear?
2) How much are you rounding the tire edges (inside and outside edges) after truing the tires?
3) What ride height are you running (front, middle, and rear)?
-Rich
1) What size tires are you running front and rear?
2) How much are you rounding the tire edges (inside and outside edges) after truing the tires?
3) What ride height are you running (front, middle, and rear)?
-Rich