BMI's DB12R

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Old 11-10-2008, 05:48 AM
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Hi guys!

Just thought I'd chime in after a busy weekend at 360 Raceway.

As everyone else has said so far, the changes Jason made to the DB12R have definitely improved the handling of the car. The setup I used on the car was actually more of a conventional setup than what I used at SnowBirds. The car was VERY smooth and very easy to drive. I still do have to work on fine tuning some things to my liking, but that'll come with more track time.

It was also fitting to be able to mix it up with the likes of Donny, Jari, and Dave G. They were all quick and made the racing exciting.

Anyway, you guys won't be disappointed with the update. The changes really did help the car.

And no, the car I ran at Cleveland was not the UPDATED car.
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Old 11-10-2008, 06:32 AM
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Originally Posted by protc3 View Post
... You can send your chassis back to me and i will add the new front mounting holes for the flex plates for $10.00 so you can now use the linear position. ....cool:
If that does help convince anyone to run this Chassis over ther other what will. I've been in a out of this sport for 15 years and I don't recall ever seeing anything like this from a chassis manuf.

Great job and support!!
E
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Old 11-10-2008, 07:33 AM
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Thanks buddy. I dont want to see anyone feel like they have to spend more money if they dont have to.
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Old 11-10-2008, 07:42 AM
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Originally Posted by EricF View Post
If that does help convince anyone to run this Chassis over ther other what will. I've been in a out of this sport for 15 years and I don't recall ever seeing anything like this from a chassis manuf.

Great job and support!!
E
The only thing that comes to mind that is similar was when Trinity would mill out battery slots and a hole to lower the motor in a Losi Streetweapon chassis back before Losi did it themselves on the IWC version of the car. I think it around $20 per chassis to have them milled out.
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Old 11-10-2008, 05:16 PM
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Jason,

In your opinion is a "gear ratio a gear ratio" or does running different size spurs give you different results in terms of torque? Assuming the rollout is exactly the same in all situations.

Hope that makes sense...

Jeremy
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Old 11-10-2008, 05:36 PM
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I've heard this in the past that a bigger spur will give more torque because it has more leverage on the axle and that a smaller spur will be higher top speed due to the smaller mass of the gear. Personally I think the torque theory cancels itself out. I'd have to do the math to figure it out for sure. Think of it this way, yes a larger spur is going to have more leverage on the axle but to keep the same roll out or gear ratio means going to a bigger pinion as well, and the motor is going to have a harder time turning the bigger pinion. My guess is that the 2 cancel each other out.

On the flip side a case can be made that a smaller spur will give you both more top end and torque due to it's lighter mass makes it easier to spin. But then the same question comes into play...does the effect of the reduced mass outweigh the reduction of leverage from the gear.

Even if they don't cancel each other out, any gain would be so minor as to be nearly indetectable...Anyway that's my theory
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Old 11-10-2008, 05:44 PM
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Hey Jason

Sweet!!! great news, cant wait to get one for sure


Originally Posted by schreff View Post
Hi guys!Just thought I'd chime in after a busy weekend at 360 Raceway.

As everyone else has said so far, the changes Jason made to the DB12R have definitely improved the handling of the car. The setup I used on the car was actually more of a conventional setup than what I used at SnowBirds. The car was VERY smooth and very easy to drive. I still do have to work on fine tuning some things to my liking, but that'll come with more track time.

It was also fitting to be able to mix it up with the likes of Donny, Jari, and Dave G. They were all quick and made the racing exciting.

Anyway, you guys won't be disappointed with the update. The changes really did help the car.

And no, the car I ran at Cleveland was not the UPDATED car.
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Old 11-10-2008, 05:45 PM
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Old 11-10-2008, 06:04 PM
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Originally Posted by Jeremy Otis View Post
Jason,

In your opinion is a "gear ratio a gear ratio" or does running different size spurs give you different results in terms of torque? Assuming the rollout is exactly the same in all situations.

Hope that makes sense...

Jeremy
I understand what you mean. Gear ratio is gear ratio to an extent. You can get the same gear ratio with a 100 spur as you can with an 88 but the larger the pinion(that you need with a 100 spur) will make the motor freewheel so to speak and have the effect of a large flywheel. This helps keep up your corner speed. I always try to run the largest spur i can that will allow me to achieve my desired rollout.
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Old 11-10-2008, 06:05 PM
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New Parts, New Parts, New Parts.... Jason you have done it again!!! The only question for me good buddy is when can I get my 'grubby lil hands on them".

Great to hear about how well they worked and congrats Schreff on another great race!! Please tell Yari that he better be back at the Carpet Nats in March at the Gate and that I said hi.
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Old 11-10-2008, 10:54 PM
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The larger you can get both the spur gear and the pinion, the more efficient the drive. Large spur/pinion combinations allow more teeth to be in contact, so sharing the load and reducing the angles of approach and departure of the teeth. This is also what you see as Jason's 'freewheel' effect - it is a smoother mesh so it will roll better.

However - the larger the spur and pinion together, the larger the rotating weight and so the slower the acceleration of the drive train. For our purposes, this can be ignored, and the weight difference is very small compared to the overall weight of the rear axle in total.

The leverage effect of a large spur is a spurious argument. These are rotating forces, not linear ones, and the 'leverage' is about the ratio itself, not the sizes of the spur and pinion. If your surmise was correct, a vehicle gearbox would be twice the size to take advantage of this effect!!

The advantages are miniscule, ceratinly less than one missed apex or one clipped corner marker. Find a ratio that works using what you have in your box and drive better - that'll get you the results!! HTH
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Old 11-11-2008, 02:25 AM
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Originally Posted by SlowerOne View Post
The leverage effect of a large spur is a spurious argument. These are rotating forces, not linear ones, and the 'leverage' is about the ratio itself, not the sizes of the spur and pinion. If your surmise was correct, a vehicle gearbox would be twice the size to take advantage of this effect!!
Well like I said the advantages or disadvantages pretty much wash themselves out...leverage may not be the proper term but the effect is the same which is why people claim to have more torque with a larger gear. The force applied to the tooth of a gear is essentially perpendicular to the radius of the gear. So if you think about it as the tooth being a lever arm used to turn the axle then you can see how the longer lever arm is easier to turn the axle, hence the thinking that a large spur gear gives you more effective torque then a smaller one.

But again as I said what really matters is the ratio itself...getting the same ratio with a small spur gear or a large spur gear is so minimal in difference that you really won't be able to notice it.
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Old 11-11-2008, 04:11 AM
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Originally Posted by SlowerOne View Post
The larger you can get both the spur gear and the pinion, the more efficient the drive. Large spur/pinion combinations allow more teeth to be in contact, so sharing the load and reducing the angles of approach and departure of the teeth. This is also what you see as Jason's 'freewheel' effect - it is a smoother mesh so it will roll better.
So lemme see if I got this right. If the larger gears roll better, then the car will maintain more momentum off power, requiring less throttle and energy to get back up to speed. Is this where the efficiency comes from?
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Old 11-11-2008, 07:32 AM
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Hey Guys,

Here is a few pics of our updated parts on a car that is all wired up for brushless so you can see how neat the wiring can be with the new layout. Also enclosed is a pic of the new silva bladder shock that we are now carrying.
Attached Thumbnails BMI's DB12R-db12rr1.jpg   BMI's DB12R-db12rr2.jpg   BMI's DB12R-db12rr3.jpg   BMI's DB12R-silva-shock.jpg  
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Old 11-11-2008, 07:39 AM
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SWEET Pic's!!!!
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