BMI's DB12R

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Old 12-27-2007, 11:56 PM
  #3451  
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Originally Posted by Scottrik View Post
I will point out for folks like myself who go to lengths (no real rational reason, just do) to avoid Futaba. The KO PDS-949 servo has the same case dimensions and output spacing as the Futaba servos so it bolts right into the BMI chassis as-delivered very nicely.

The JR servos, though, require flat mounting w/glue, etc or other re-engineering/re-drilling.

Scottrik

Yes,The KO is a real nice one also. I have one of those also. The futaba is an awesome servo also bro. No need to be hating.
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Old 12-28-2007, 09:55 AM
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Where can you get sur-lube?

Thanks
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Old 12-28-2007, 10:19 AM
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irs and wind tunnel are the 2 sources for sure lube. wind tunnel, you can buy just the ones you want
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Old 12-28-2007, 10:24 AM
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Hey Yang are you running the birds
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Old 12-28-2007, 10:30 AM
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Jason,
Have you thought about redesigning the rear pod brackets to lower the axle a couple millimeters? On the BMI DB12R I can get the rear tires down to just under 1.7" and still maintain a 3.5mm ride height with the 3.5 IRS spacers. I also have a CEFX C12 car and I can easily run tires down to 1.6" with a 3.5mm ride height. I measured the difference in the vertical axle hole on both the BMI and CEFX rear pods from the bottom plate but I can't remember the exact difference. If I remember correctly, I think it was 1.4mm.

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Tom
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Old 12-28-2007, 10:35 AM
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Originally Posted by Chemical X View Post
Jason,
Have you thought about redesigning the rear pod brackets to lower the axle a couple millimeters? On the BMI DB12R I can get the rear tires down to just under 1.7" and still maintain a 3.5mm ride height with the 3.5 IRS spacers. I also have a CEFX C12 car and I can easily run tires down to 1.6" with a 3.5mm ride height. I measured the difference in the vertical axle hole on both the BMI and CEFX rear pods from the bottom plate but I can't remember the exact difference. If I remember correctly, I think it was 1.4mm.

Thanks,
Tom
I was wondering the same thing because I still have quite a bit of foam left when im at 3.5 ride hieght with the IRS 3.5
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Old 12-28-2007, 10:45 AM
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Originally Posted by ChestyV32 View Post
Hey Yang are you running the birds
I want to, but it is the wrong time of the year for me.
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Old 12-28-2007, 11:01 AM
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Originally Posted by Chemical X View Post
Jason,
Have you thought about redesigning the rear pod brackets to lower the axle a couple millimeters? On the BMI DB12R I can get the rear tires down to just under 1.7" and still maintain a 3.5mm ride height with the 3.5 IRS spacers. I also have a CEFX C12 car and I can easily run tires down to 1.6" with a 3.5mm ride height. I measured the difference in the vertical axle hole on both the BMI and CEFX rear pods from the bottom plate but I can't remember the exact difference. If I remember correctly, I think it was 1.4mm.

Thanks,
Tom


I will look at it. I went with this location for optimal performance range with axle height. It was kind of a tradeoff. I tried a few different axle heights and found as i got lower the performance started to suffer. The drive created by the rear axle and its height around the CG has an effect on the handling of the car and i tried to run the axle where it would work best and at the same time, i needed to average the travel to accomodate all the size ride height adjusters. This seemed to be the sweet spot. I know its not ideal if you want to run super small tires. You can run them real small but the tires have a point at which they can get too small and effect the performance of the car. I wanted to stay away from that. I will see if i can get them a little lower without a big sacrifice.
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Old 12-28-2007, 11:31 AM
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Originally Posted by protc3 View Post
I will look at it. I went with this location for optimal performance range with axle height. It was kind of a tradeoff. I tried a few different axle heights and found as i got lower the performance started to suffer. The drive created by the rear axle and its height around the CG has an effect on the handling of the car and i tried to run the axle where it would work best and at the same time, i needed to average the travel to accomodate all the size ride height adjusters. This seemed to be the sweet spot. I know its not ideal if you want to run super small tires. You can run them real small but the tires have a point at which they can get too small and effect the performance of the car. I wanted to stay away from that. I will see if i can get them a little lower without a big sacrifice.
Now that's some excellent real time customer service and feedback.

I'm surprised how well you guys managed to fulfill and process the online orders during the holiday hours.
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Old 12-28-2007, 11:53 AM
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Originally Posted by protc3 View Post
I will look at it. I went with this location for optimal performance range with axle height. It was kind of a tradeoff. I tried a few different axle heights and found as i got lower the performance started to suffer. The drive created by the rear axle and its height around the CG has an effect on the handling of the car and i tried to run the axle where it would work best and at the same time, i needed to average the travel to accomodate all the size ride height adjusters. This seemed to be the sweet spot. I know its not ideal if you want to run super small tires. You can run them real small but the tires have a point at which they can get too small and effect the performance of the car. I wanted to stay away from that. I will see if i can get them a little lower without a big sacrifice.
Thanks Jason. Obviously I wouldn't want any negative impact to the performance of the car. Did you see a performance difference with the axle height between an asphalt car versus a carpet car?

For reference, I'm running GQ tires which do not use the large wheel like the Jaco Prisms or Parma Pro-38s. I still have quite a bit of tire left when they're between 1.6" and 1.7".
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Old 12-28-2007, 12:01 PM
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Originally Posted by fav0re View Post
Now that's some excellent real time customer service and feedback.

I'm surprised how well you guys managed to fulfill and process the online orders during the holiday hours.
Thanks buddy. We do our best.
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Old 12-28-2007, 12:02 PM
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Originally Posted by Chemical X View Post
Thanks Jason. Obviously I wouldn't want any negative impact to the performance of the car. Did you see a performance difference with the axle height between an asphalt car versus a carpet car?

For reference, I'm running GQ tires which do not use the large wheel like the Jaco Prisms or Parma Pro-38s. I still have quite a bit of tire left when they're between 1.6" and 1.7".
Ahh, I see. I havent run GQ tires. I didnt realize anyone was still using the small wheel. That explains it better to me. I just checked and with the big wheels you can run the tires real low.
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Old 12-28-2007, 12:03 PM
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Yes, I find that running the axle higher on asphalt created more rear grip on power.
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Old 12-28-2007, 03:05 PM
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Hey guys,

I just got word that the BMI T shirts will be delivered tommorow and will be ready for sale. I will get them on the website this week. They are real nice. Printed front and back
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Old 12-28-2007, 03:51 PM
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OK Jason (and assorted sages).

Here's what's bugging me.

When siting components on the chassis we do so with balance devices to get the side-to-side balance equal. Pretty much every chassis has balance holes at the front lip and the rear edge of the rear pod.

MY quandry is that I really think we should be balancing the main chassis plate and everything on it IRRESPECTIVE of the rear pod and it's symetric attachments to the main plate. Don't get me wrong, I appreciate that the rear pod should be as balanced as possible but my belief is that:

a) the rear pod balance is what it is, really, other than adding weight we have not say in it other than to change motor brand/type

b) regardless it's balance (or lack thereof) it is sitting flat supported by the straight axle we are limited to by rule.

I'm thinking I should be balancing the chassis main plate and it's components by itself since it is, essentially supported by the front wheels via the suspension there and the rear pivot. To do so I'll add a hole to my main chassis plate ahead of the pivot screw to accept my balance buttons.

Really I should be able to do this without the components on the centerline (shock, antenna/mount, battery brace) OR the symetric stuff (front suspension, side wings, hockey sticks, pivots, etc. If this works I should be able to take the main plate with the servo, servo-saver and linkage attached then balance it out with my receiver, esc and related components (caps, diodes, etc). THEN assemble the rest of the car around this.

If I'm clearly goofy please feel free to point this out but be sure to explain why. I've been puzzling on this for a while now and just can't see how I'm mistaken.

Thanks,

Scottrik
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