| [GMCnet] Dreaming of overdrive [message #219294] |
Tue, 20 August 2013 16:33  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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No matter how you do it, the key is to be able to run numerically higher gearing while under load (climbing a mountain) to reduce the internal stresses on the engine while also being able to run numerically lower gearing while not under load to increase fuel efficiency. With only three gears to select from it is really hard to do both with a 12,000 bread box going down the road. If the jumps between gears is too great, it won't work well and if the jumps are too small it won't be worth the effort. Just ask any bicyclist. The right combination is the gearing that will allow a nearly constant cadence going up hill, on the flat or going down hill. What changes is the speed/distance you travel. Same is true for our coaches. With a fourth gear available one can better match the gears to the available RPMs (cadence in the bicycle analogy) than one can do with only three gears available. If you were willing to put up with a top end of 50mph, it would be relatively easy to pr
operly gear for climbing mountains with just three speeds. But, since we seem to want a top end closer to 70mph three speeds are not enough except on relatively flat land unless you have the ability to generate a lot of torque and are willing to tolerate a lot of internal engine stress. Seems to me that our engine/transmission/final drive pairings have worked really well for 40 years and would only get better with a forth gear, no matter how we get there. My take anyway......
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
541-499-1027
541-592-5360
===============
Message: 16
Date: Tue, 20 Aug 2013 15:34:06 -0500
From: Glenn Giere <glenngiere@gmail.com>
Subject: Re: [GMCnet] Dreaming of overdrive
To: gmclist@temp.gmcnet.org
Message-ID: <3588c.5213d2be@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
I'm confused. What possible advantage would there be to overdrive? The right rear end ratio or addition of the power drive will put cruising RPM in the mid to upper 2000's, what more could you want?
Glenn
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Jerry & Sharon Work
78 Royale
Kerby, OR
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