Reply
 
Thread Tools Display Modes
 
Old 01-18-2016, 03:33 PM   #11
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 6,179
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
Fifth gear on a newer Allison is .71 overdrive. Sixth gear is .61 OD. Engine speed limiting is typically done by governing the RPM's. At 1800 RPM, the difference between .71 (59 mph in 5th gear) & .61 (68 mph in 6th gear) makes for about 9mph difference on my rig but different tire sizes and rear axle ratios will produce different results. But in any case, the OD difference will produce more speed at any given RPM number.

Does any of that make any sense?
Tango is offline   Reply With Quote
Old 01-18-2016, 04:13 PM   #12
Bus Crazy
 
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,328
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
Wow, they've made the second OD even higher?! That would be pretty awesome if the engine doesn't mind making the torque to keep things moving through a 0.61 ratio.

Regarding the speed limiting: among engine ECMs that support road speed limiting, some support two levels of limit. They can have one speed limit for normal operation and a second limit for cruise control operation. Apparently the idea is to incentivize fleet drivers to choose cruise control because of its fuel economy $$ savings for the fleet operator. The truck is programmed with a higher max speed which can be reached by enabling cruise control and then pushing the "accelerate" button, but cannot be reached by mashing the accelerator pedal with cruise off. I think my Cummins ECM has this feature.. I vaguely recall setting two different limits to the same number.

Engine RPM limit is of course still present as well. I left that one alone on mine.
family wagon is offline   Reply With Quote
Old 01-18-2016, 04:59 PM   #13
New Member
 
Join Date: Jan 2016
Posts: 5
At the end of the day, there is probably a monetary reason. On Allison's side it was probably cheaper to make on tranny vs a 5 & a 6 speed. I'd be willing to bet since there is only one tranny, Allison charges the builders a premium for sixth, which isn't needed for most municipalities. On the coach builder's end, I'd bet there was a liability insurance reason for having a hard lockout. These are designed to carry up to 80 children at a time. Nobody would want a school bus doing 75 fully loaded. All of this is pure speculation.
cbear is offline   Reply With Quote
Old 01-18-2016, 09:20 PM   #14
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 6,179
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
As previously noted...it was the speed rating of typical school bus tires that Allison used as the limiting factor.
Tango is offline   Reply With Quote
Old 01-19-2016, 02:08 AM   #15
New Member
 
Join Date: Jan 2016
Posts: 5
It seems peculiar that Allison's concern is the tires. Allison requires the OK from the coach builder, who has no idea what tires are on an old bus. I'm not saying you're wrong, it just seems like a flawed process. I would think anyone could get sixth gear unlocked if they had a shop verify that the tires were upgraded.
cbear is offline   Reply With Quote
Old 01-19-2016, 10:27 AM   #16
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 6,179
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
It was not an engineering issue..it was the liability as regards school districts and the V rating on the tires they typically use. Once they are out of service in a school district and the tires are upgraded the tranny should be able to be unlocked (re-programmed) but it is a hassle for Allison to verify so they don't do it often. Is it done? Yes, but usually by a hacker/builder...not Allison. I posted a chap's name & link here maybe a year ago who does them routinely. Can't recall it anymore but it should be buried here somewhere. He was the one who told me what Allison's position was.
Tango is offline   Reply With Quote
Old 01-19-2016, 02:58 PM   #17
Site Team
 
Join Date: Jul 2014
Posts: 694
Year: 1998
Coachwork: Bluebird
Chassis: TC2000 RE
Engine: 8.3l Cummins
Rated Cap: 78
In many of the combinations, the engine has no ECU and is entirely mechanical. There's no easy way to prevent the engine from turning higher rpm in specific gears, thus lockout of the topmost gear.

Quote:
Originally Posted by Booyah45828 View Post
The speed limit thing is a good point. But that doesn't answer the question of why no 6th. If they were worried about speed, they could simply select the speed limiting feature in the control module, then they you would input the tire size(revolutions/mile) and the engine wouldn't be allowed to turn over X amount of rpm in Y gear.

It just doesn't make sense to me why you would go about limiting the speed by eliminating a gear.
aaronsb is offline   Reply With Quote
Old 01-20-2016, 08:09 AM   #18
Mini-Skoolie
 
Join Date: Nov 2014
Location: South Cacalackey
Posts: 47
Year: 1999
Coachwork: Thomas
Engine: Cat 3126
Rated Cap: 72
Quote:
Originally Posted by Scooternj View Post
Ever wonder why those of us with computerized buses need authorization from manufacturers before we can tinker with the computer's programming (particularly locked double overdrive on MD3060 trannies from Allison)? Because of copyright laws, something that needs to be fixed, as explained in this blog on Slate

Is it bad that I have been since I can remember...

When I was in first grade, I took apart an RC car and receiver which was and still is governed by strict fcc codes, attempted to make the car faster by pumping more batteries into it. I also, broke the law when I put way more power through the transmitter than was required because I wanted to race my car all the way to the end of the street. So my first grade self should have been fined and jailed.

It's commonplace for kids under 18 to have loads of copyright 'infringed' material. This kind of stupid crap just goes to point out how ignorant and how detached Americans are from our politics, because our politics are just a giant joke with so many things that are morally fucked that it's not even funny.. Why? Greed and money... here's one solution i have found, but I haven't looked into how effective it can be or how legitimate it is... Looking into it. Action is the only way you can change this crap... Or join the trolls, file a patent that's so similar to the company owned design, then sue them for infringement.

I have read article after article of people being sued, and even their entire lives ruined because they left their wifi open (copyrighted porn)... sued isn't the worst part. The government is trying to put innocent people in prinson (child pornography, takes a linux laptop and 5 minutes to break any wifi pass). I'd go thorugh and find you some links... but a) i have read these articles years ago, and b) I don't have the time. C) i'm not going to go to the length it takes to CYA on linking you to the programs to crack the wifi.

What I WILL do though is let you know that your sources need polished and you also need to go hunt down the sources of the information in these articles... Often times the source chain is circular Look at the click bait on that web page. That's not a realiable news outlet. I'm sorry, it's just ...

pubmed is a great source for research articles (the source) and you can find out who FUNDED THE PROJECT

arstechnica.com is a good all around reasonable outlet for news.
Nachowarrior is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Virginia Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 05:33 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.