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Old 10-25-2009, 03:13 PM   #8011
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Last edited by Josh Keller; 10-28-2009 at 06:22 PM.
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Old 10-25-2009, 05:02 PM   #8012
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If anyone's interested, a have a couple DB12rrs Im selling.
-+-2 BMI DB12rr's For Sale-+-
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Old 10-25-2009, 05:10 PM   #8013
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Hey folks,

So after some terrible handling issues I have sorted out with the above help, today the car was ballisticly fast, just a tenth off the pace of the fast guy at the track, and I was over geared, and not as good of a driver.

So besides for getting the car on point and making it quite a rocket, I again have had a rash of busted flex plate pivot ball cups. Today I had 2 break.

The track we run has about a 60 - 70ft straight leading into a 90 deg sweeper to another 20 - 30 ft of track, if you catch a bump or any issue in the entrance to the sweeper you end up going right to the wall. Twice I contacted the wall today and twice it busted the pivot ball cup on the side of the car that contacted the wall.

I am thinking of trying some thin aluminum tubing and hammering a section over the outside of the Delrin lower pivot ball holder to see if that will hold it together better.

The hits my car took against the wall were less severe than what some CRC and even an old Hot Bodies Tbar cars took today yet they rolled away. This caused me to retire from the main today and the 3rd qualifier.

The balls floated free in the holder, no binding, the pivot ball on the opposite side did not busted out if its housing, no other ailments to the car other than that. Just really confused what makes these seemingly standard side strikes so destructive to the car, its almost like I need some large Nerf bars installed.
So in an answer to my own post, I think I found a solution for this:

http://www.mcmaster.com/#6622k711/=47wv55

Cutting some of the above SS tube into 1 - 2mm slices, you could force that over the outside of the standard delrin ball cup. It will be tight but should do fine in giving some very strong extra support to the delrin cup.

I have a couple tubes on order, one Al and 2 flavors of SS (312 and 304) to give a try. I think the hardest part will be getting consistent sub 2mm slices of the material. I need to hone my dremel skills
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Old 10-26-2009, 12:02 AM   #8014
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Great racing today out here. My DB12RR was handling exceptionally well and I turned in some really good laps. Unfortunately in a traffic incident the ball cup came off the shock so I wasn't able to place as well as I would have. Just one of those things that happens. So I'm still quite pleased because the car was just a pleasure to drive. Additionally we received some good news today from the LHS we run our race in..we are now allowed to run LiPo! So my LiPo chassis is going back on the car
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Old 10-26-2009, 03:15 AM   #8015
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Hi Joe

If you are cutting thing Al tube then you can use a sharp knife. Just role the tube back and forward by putting pressure on it with the knife. It will cut a nice ring. Clean up the inside and away you go.

Also i broke both standard L plates by hitting the boards side on. I think one broke early and then another later. The pivot ball holders were not damaged at all
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Old 10-26-2009, 03:40 AM   #8016
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Hey all, I have raced T-bar, L-bar, and I think gaga bar
I realized if you hit the right spot something will break, even the most unlikely of things. Sometimes it takes a big crash and sometimes just a tap. Don't forget if you strengthen one spot then the next weak spot will break. A friend kept breaking body posts on his TC car. He could have put aluminum posts but then the shock tower would break being the next weak joint. So be careful when strengthening certain parts...

On a different note has anyone tried a 3.5T motor with 1S Lipo? Is it as fast as 4.5T/5T 4-cells and does it last for 8 minutes?

Thanks,
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Old 10-26-2009, 04:41 AM   #8017
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Originally Posted by PHI/BMI racer View Post
On a different note has anyone tried a 3.5T motor with 1S Lipo? Is it as fast as 4.5T/5T 4-cells and does it last for 8 minutes?

Thanks,
I havent tried 3.5 yet but 4.0 It makes runtime easy. 3.5 will be a different story though. This was on a medium - large outdoor asphalt track. The speed was similar to a 5.5 4cell car.

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Old 10-26-2009, 06:09 AM   #8018
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I havent tried 3.5 yet but 4.0 It makes runtime easy. 3.5 will be a different story though. This was on a medium - large outdoor asphalt track. The speed was similar to a 5.5 4cell car.

Antoni
Thanks, will give it a go, we run asphalt only, and most tracks are medium tracks with one straight and the rest very flowing.

Ciao
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Old 10-26-2009, 08:06 AM   #8019
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Originally Posted by PHI/BMI racer View Post
Hey all, I have raced T-bar, L-bar, and I think gaga bar
I realized if you hit the right spot something will break, even the most unlikely of things. Sometimes it takes a big crash and sometimes just a tap. Don't forget if you strengthen one spot then the next weak spot will break. A friend kept breaking body posts on his TC car. He could have put aluminum posts but then the shock tower would break being the next weak joint. So be careful when strengthening certain parts...

On a different note has anyone tried a 3.5T motor with 1S Lipo? Is it as fast as 4.5T/5T 4-cells and does it last for 8 minutes?

Thanks,
Yep Yep, I am well aware of the whole weak point/stong point dynamic. My thought is the car as a whole is strong enough to handle a bigger hit, and if I do break flex plates now instead, they are cheaper than these machined delrin ball cups at almost $16.00 a pair. Of course my goal is to not tap the boards, but if you are trying to push on the limit, you do hit the wall some times. I just need to know that any small/med hit to the rear pod wont take me out of the race.

I am going to use the 304 stainless cut into 2mm rings and forced over the delrin pivot housing. From looking at the chassis there is more than enough room for that extra material.
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Old 10-26-2009, 08:06 AM   #8020
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I'm having a handling issue that I'm trying to sort out. I'm running mod carpet that gets to be pretty high bite by the end of the day. The issue is when the bite comes up the car lifts the inside rear tire and pirouettes on outside front tire. The problem isn't really bad but here's what happened. I was leading for the first two minutes and needing a little more steering to fend off the guy behind me I added another click or two of dual rate and then it lifted the rear tire and caused a 4 car place pile up. Taking out those two clicks it never happened again but the car had a significant push placing me in 2nd, 2 seconds out of the lead.

Everything else seems to be good, its just when the bite comes up, if I don't dial out a lot of front grip, it will pirouette on the front tires. I went down in the damper tubes to 5k, 10k on the kingpins, next harder front tire, and almost no traction compound on the front. This helped to make the car drivable, but it was over a full lap slower than my TQ run in the 2nd round (when the car was perfect, then it turned evil in the 3rd round and I had to chase it for the main). It never traction rolled either. Any suggestions to get the steering back without causing it roll or spin out?
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Old 10-26-2009, 08:37 AM   #8021
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Originally Posted by gubbs3 View Post
I'm having a handling issue that I'm trying to sort out. I'm running mod carpet that gets to be pretty high bite by the end of the day. The issue is when the bite comes up the car lifts the inside rear tire and pirouettes on outside front tire. The problem isn't really bad but here's what happened. I was leading for the first two minutes and needing a little more steering to fend off the guy behind me I added another click or two of dual rate and then it lifted the rear tire and caused a 4 car place pile up. Taking out those two clicks it never happened again but the car had a significant push placing me in 2nd, 2 seconds out of the lead.

Everything else seems to be good, its just when the bite comes up, if I don't dial out a lot of front grip, it will pirouette on the front tires. I went down in the damper tubes to 5k, 10k on the kingpins, next harder front tire, and almost no traction compound on the front. This helped to make the car drivable, but it was over a full lap slower than my TQ run in the 2nd round (when the car was perfect, then it turned evil in the 3rd round and I had to chase it for the main). It never traction rolled either. Any suggestions to get the steering back without causing it roll or spin out?
Make your front end as wide as you can get it. Also glue the inside and outside of your front tires. Whole way to the top. And then round them off just a little.
You might want to use a 5 block on the front end. It calms the car down on turn in over the 10 block. But, before trying the blocks try one hard front spring to stop the car from digging in.
Hope this helps.
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Old 10-26-2009, 10:07 AM   #8022
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Originally Posted by gubbs3 View Post
I'm having a handling issue that I'm trying to sort out. I'm running mod carpet that gets to be pretty high bite by the end of the day. The issue is when the bite comes up the car lifts the inside rear tire and pirouettes on outside front tire. The problem isn't really bad but here's what happened. I was leading for the first two minutes and needing a little more steering to fend off the guy behind me I added another click or two of dual rate and then it lifted the rear tire and caused a 4 car place pile up. Taking out those two clicks it never happened again but the car had a significant push placing me in 2nd, 2 seconds out of the lead.

Everything else seems to be good, its just when the bite comes up, if I don't dial out a lot of front grip, it will pirouette on the front tires. I went down in the damper tubes to 5k, 10k on the kingpins, next harder front tire, and almost no traction compound on the front. This helped to make the car drivable, but it was over a full lap slower than my TQ run in the 2nd round (when the car was perfect, then it turned evil in the 3rd round and I had to chase it for the main). It never traction rolled either. Any suggestions to get the steering back without causing it roll or spin out?
Hey,
if your back end bites too much then you can traction roll. Try making the rear stiffer... Center spring harder helped my car a lot, loosened the back just enough to go fast in the corners without sliding out.
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Old 10-26-2009, 10:36 AM   #8023
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In my testing and trying to resolve this same issue, I found that if you stiffen the rear to the point that the ass end never wants to traction roll, then you have too little grip. The way I have my car setup now is it wont traction roll if I Drive a smooth and consistent line. If I square off a corner, turn in late, early apex, then I could end up rolling the car as I have to dump tons more steering in.

Once i focused on a nice consistent line, I didnt roll anymore. When I stiffened the car to the point the ass end didnt have that bite, then by the 5 minute mark the car was very twitchy as the tires lost just enough grip to make the car extremely slippery.

Compared to more standard suspension designs I find the BMI to be harder to setup, but when it is setup, its blisteringly fast, and potentially the best car on the market.
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Old 10-26-2009, 04:17 PM   #8024
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Hey folks,

So after some terrible handling issues I have sorted out with the above help, today the car was ballisticly fast, just a tenth off the pace of the fast guy at the track, and I was over geared, ...
ok, so spill the beans. what did you figure out that was causing you troubles and what changed to make things better?
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Old 10-26-2009, 04:41 PM   #8025
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ok, so spill the beans. what did you figure out that was causing you troubles and what changed to make things better?
The changes that were made where:

Went one step lower on the forward shock mount
Harder (red) spring installed
Moved the servo to the rearward mount but still flat on the chassis. This changed weight distribution (more to the rear), and ackerman.

That was about it. That and I corner weighted the car with 4 scales and added about 8 gm of lead on the Rx side.

But the bigges thing I did to improve the car... was focus on my line more and stop being so harsh on the turn in. I also turned my DR down (at about 55% now) even when running Black fronts /Yellow rears.

I did testing wtih Magenta all around, 2x Pink F / Magenta R, Purple F/Magenta R but they all lost grip and fuzzed up toward the end. Black and Yellow were faster through the entire race.
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