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Author: Subject: BEC Reverse Boxes
scootz

posted on 14/10/09 at 10:56 AM Reply With Quote
BEC Reverse Boxes

I occasionally read that these sap power - is it noticeable, can anyone hazard a guess at a potential loss percentage?
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roadrunner

posted on 14/10/09 at 11:33 AM Reply With Quote
you want to go to MNR, i have seen theres and there is no loss of power at all.
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Gav

posted on 14/10/09 at 11:34 AM Reply With Quote
Check this thread






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scootz

posted on 14/10/09 at 11:37 AM Reply With Quote
Cheers!
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designer

posted on 14/10/09 at 02:13 PM Reply With Quote
Surely it's impossible to pass power through gears and not loose power!

It's surely a matter of their box consuming less power than all the other options.

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Gav

posted on 14/10/09 at 02:16 PM Reply With Quote
Mark states the MNR box lose is ~11%.

0 would be a little optimistic






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Frosty

posted on 14/10/09 at 03:16 PM Reply With Quote
Someone on the Westfield forum did a calculation of just how hot the reverse box would get if it absorbed 10% of power.

On your typical 150bhp BEC, this is 15bhp.

As we all know, you cannot destroy energy, you can only convert it. So you would convert nearly all of the 15bhp of movement energy into heat energy?

15bhp is 11.2kw. An 11.2kw heater would be so incredibly hot that it would melt things. A 11.2kw loss from the reverse box alone just isn't possible I shouldn't think. Not when the entire drive train (diff, CV joints, wheel bearings, tyres, and prop shaft) adds up to a typical 15%.

So although they loose a small amount, it would merely contribute to the overall losses by a tiny amount. Exactly how much is hard to say, but they are dog gears in reverse boxes, and only a very small amount of oil (125ml in a Westfield box) to cause drag.

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franky

posted on 14/10/09 at 04:25 PM Reply With Quote
Think you loose about 3ish bhp. someone with an early r1 motor and the MNR box made 130bhp at the wheels. A bike only makes about 132ish bhp.
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BenB

posted on 14/10/09 at 04:34 PM Reply With Quote
Don't forget they also make a bit of noise. But noise is quite easy to make (ie 500W of noise is a hell of a lot). So heat is going to be the main thing produced......
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G.Man

posted on 14/10/09 at 11:30 PM Reply With Quote
quote:
Originally posted by Gav
Mark states the MNR box lose is ~11%.

0 would be a little optimistic


That is the total transmission loss, axle/shaft/bike gearbox/reverse box.

The MNR box reduced the transmission loss by 4%ish I think he said compared to the "other popular leading brand".





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Everyone has one, nobody wants to hear it and only other peoples stink!

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Gav

posted on 15/10/09 at 08:56 AM Reply With Quote
I stand corrected






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rob2005

posted on 15/10/09 at 02:57 PM Reply With Quote
If your gonna get one avoid the quaife its the only thing that drives me nuts on my car.

First thing i will do in the new year is remove it and buy an MNR box.





Fortune favours the brave!!

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motorcycle_mayhem

posted on 15/10/09 at 09:24 PM Reply With Quote
I remember placing something on the WSCC site, in some disbelief that so much power could be dissipated through the reverse gearbox without extreme heat. Just before I fitted one of those lightweight AB things instead of my WF chocolate gearbox.

OK, so I have rolling road plots with and without, albeit not on the same day, but the same week. Result was no noticeable power gain with the electric reverse in place of the WF box. Period.

BUT the difference in how it drives, the feel, lack of vibes, lack of noise, lack of backlash, etc., lack of oil p@@@ing everywhere. I'm pretty sure it accelerates and decelerates quicker, but that's all part of the 'feel', not a measurable thing. Prise my electric reverse from my cold dead fingers.

Circuit times have improved anyway, 2009 over 2008 (change point).

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yahshuatwo

posted on 16/10/09 at 02:37 AM Reply With Quote
I'm running an older gen I box (FR 2000) and here's what I've discovered:

* occasional backlash-thrusting in 1st gear
* Some oil leakage
* input/output flanges require occasional re-fastening
* NO vibration
* NO noise (helical gearing)

I'm developing a new reverse box in the USA and hopefully my design will clear for the oil leakage many of today's boxes

[Edited on 16/10/09 by yahshuatwo] Rescued attachment inline_reverse.jpg
Rescued attachment inline_reverse.jpg

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sucksqueezebangblow

posted on 16/10/09 at 08:57 AM Reply With Quote
quote:
Originally posted by designer
Surely it's impossible to pass power through gears and not loose power!

It's surely a matter of their box consuming less power than all the other options.


The MNR box is a clever design as it is a straight through shaft in forward gear so no more resistance or friction than a propshaft centre bearing. It only operates through gears in reverse, which of course gives more resistance but dosen't matter (unless you're going for the reverse speed record)!





Better to Burnout than to Fade Away JET METAL ~ AndySparrow

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G.Man

posted on 16/10/09 at 12:52 PM Reply With Quote
quote:
Originally posted by rob2005
If your gonna get one avoid the quaife its the only thing that drives me nuts on my car.



100% agree, the Q box was nasty, felt like the drivetrain had about 180 degrees of backlash in it.





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Gergely

posted on 19/10/09 at 11:38 AM Reply With Quote
The Quaife box is noisy as hell, has some play in the main rear bearing after around 800 miles, it has backlash and it spits oil out, so we had to completely modify its breather...
That said, it is much better than not having reverse and it actually works properly on an incline. My garage is under the house, and I can reverse out no problems...
Now, if I were to get my kit now, I would try the MNR box for sure...
Gergely





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:{THC}:YosamiteSam

posted on 19/10/09 at 05:34 PM Reply With Quote
does the quaife / westfield / MNR box have the same mounting centres so they are swappable? i guess the change lever mech is different - havnt seen a pic of the new MNR one - sounds interesting! -- my westy one has loads of back lash thro it - it does my head in too.. be nice to bin it and get a modern one in..
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franky

posted on 19/10/09 at 06:11 PM Reply With Quote
the MNR box has the same mountings as a quaife unit. All fittings are the same..... good planning it seems like!
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