ADVrider

Go Back   ADVrider > Bikes > Orange Crush > Crazy-Awesome almost Dakar racers (950/990cc)
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-31-2013, 10:23 PM   #811
sakurama OP
on an endless build
 
sakurama's Avatar
 
Joined: Oct 2004
Location: NYC & PDX
Oddometer: 1,431
Quote:
Originally Posted by HeatXfer View Post
Question:

Why would the front wheel pull to one side with a single drive? If that were the case, why are shaft drive bikes only driven from one side? What about that single sprocket on the rear? Single disc brakes? They don't pull to one side.

I could see a potential problem if you only had one fork, it would want to rotate axially if it were by itself, but it's prevented from rotating because the front axle is secured to the other fork. Not to mention the fork brace.

I was a large tonnage chiller mechanic for 20yrs: I understand the dynamics of rotating machinery, stabilizing devices and counteracting torque, but you guys are the engineers and fabricators: please explain how single-sided power transmission would adversely affect bike control given the other factors I stated.

Thanks in advance
It's called "torque steer" and driven rear wheels don't turn so they aren't affected. If the driveshaft was on one side the combined forces of a shaft and gear spinning in one direction would assist or fight steering based on the which way the bike was turned. By driving both sides the driveshafts cancel each other. Essentially the gear is attempting to climb the sprocket and so it will pull to that side.

When the bike is spinning the front wheel you certainly sense a stiffness from the gyroscopic forces.

Anyway I found two good articles that talk about it. One is a general one related to cars: http://en.wikipedia.org/wiki/Torque_steering

And the other is a link to a PDF of a Cycle World test of a Christini bike where the double drive shafts are discussed. It's a good article but it's older - they've refined the bikes quite a bit.

http://www.christinibicycles.com/pdf...-Christini.pdf

Maybe Chris can weigh in with a more technical answer.

Gregor
sakurama is offline   Reply With Quote
Old 03-31-2013, 10:34 PM   #812
HeatXfer
Bad knees
 
HeatXfer's Avatar
 
Joined: Feb 2008
Location: S.F. Bay Area
Oddometer: 623
Thank you, I'll read them both.
HeatXfer is offline   Reply With Quote
Old 04-01-2013, 06:45 AM   #813
buffallodan
Beastly Adventurer
 
buffallodan's Avatar
 
Joined: Nov 2004
Location: Frankfort Kentucky
Oddometer: 1,709
This just gets more and more fascinating! Awesome work guys.

Sent from my SCH-I605 using Tapatalk 2
buffallodan is offline   Reply With Quote
Old 04-01-2013, 07:32 AM   #814
wiseblood
Hall Monitor
 
wiseblood's Avatar
 
Joined: Dec 2008
Location: New York City
Oddometer: 12,428
Quote:
Originally Posted by sakurama View Post
Here's some CAD drawings I found that probably explain the system better.

That completely answers my questions! Also, you answered another question by explaining the free-wheel hub and the 70% power ratio.

Though, I imagine chain lubing / cleaning is about to become a slightly more time consuming task.
__________________
"Hard Work Often Pays Off After Time, but Laziness Always Pays Off Now."

Big Apple Tag-o-Rama Maps: Click Here!
wiseblood is online now   Reply With Quote
Old 04-01-2013, 09:30 AM   #815
sakurama OP
on an endless build
 
sakurama's Avatar
 
Joined: Oct 2004
Location: NYC & PDX
Oddometer: 1,431
Quote:
Originally Posted by wiseblood View Post
That completely answers my questions! Also, you answered another question by explaining the free-wheel hub and the 70% power ratio.

Though, I imagine chain lubing / cleaning is about to become a slightly more time consuming task.
Cool.

It's actually something we're discussing right now is the chains. They'll be smaller and we'll use two but the short one will be off the countershaft and almost completely exposed. The second longer one that will run up to the gearbox we'll make enclosed so that its not spraying lube all over inside the engine bay and so that it can live longer (enclosed chains can approach shafts in ease of maintainence and life spans) so really it should only be the short one that needs regular attention.

I have another trip planned to NYC in a couple weeks so I might use that time to pull my wheel apart and lace up the new hub. I shipped my dirt wheels to Portland so I'll need to lace that later. I'm curious to see how the bike works with the smaller 17/19 wheels on pavement (should never work except for wheelies) and on dirt where the 19 is at a disadvantage to the big wheels. It would be great if it helps the small wheel set on dirt and gravel.

Gregor
sakurama is offline   Reply With Quote
Old 04-01-2013, 09:47 AM   #816
neduro
Addict
 
neduro's Avatar
 
Joined: Jul 2003
Location: Colorado Springs, CO
Oddometer: 11,853
Quote:
Originally Posted by sakurama View Post
I'm curious to see how the bike works with the smaller 17/19 wheels on pavement (should never work except for wheelies) and on dirt where the 19 is at a disadvantage to the big wheels. It would be great if it helps the small wheel set on dirt and gravel.
Brainstorming, but what's the relative circumference difference between the 18/21 (that it is presumably designed for) vs. 17/19? I'm guessing that there's no issue, but I suppose there's a chance they could interfere?

I always felt like the machines that would benefit most from 2wd are not the ones Christini started converting. Big ADV bikes are right at the center of my list- lots of wheelspin in 1wd, a few more pounds won't make much difference (relative to a 250 lbs dirtbike), and intended use across a very wide range of intended conditions.

__________________
Doubletake Mirrors- Folding D/S mirror that is both useful and indestructible.

Dual Sport Riding Techniques DVDs: Clear instructional DVDs to improve off-road skills.
neduro is offline   Reply With Quote
Old 04-01-2013, 10:03 AM   #817
Wadester
Rides a dirty bike
 
Wadester's Avatar
 
Joined: Jun 2008
Location: 'Cruces
Oddometer: 1,925
Quote:
Originally Posted by HeatXfer View Post
Question:

Why would the front wheel pull to one side with a single drive? If that were the case, why are shaft drive bikes only driven from one side? What about that single sprocket on the rear? Single disc brakes? They don't pull to one side.

I could see a potential problem if you only had one fork, it would want to rotate axially if it were by itself, but it's prevented from rotating because the front axle is secured to the other fork. Not to mention the fork brace.

Thanks in advance
Quote:
Originally Posted by sakurama View Post
It's called "torque steer" and driven rear wheels don't turn so they aren't affected. If the driveshaft was on one side the combined forces of a shaft and gear spinning in one direction would assist or fight steering based on the which way the bike was turned. By driving both sides the driveshafts cancel each other. Essentially the gear is attempting to climb the sprocket and so it will pull to that side.

When the bike is spinning the front wheel you certainly sense a stiffness from the gyroscopic forces.

Maybe Chris can weigh in with a more technical answer.

Gregor
Torque steer is the issue - but the place it would come from would be at the headstock. If you have a single drive, it would certainly want to turn/steer in reaction to torque applied - just like the rear swingarm wants to extend downward when you apply torque.

Driving both sides of the hub is not completely necessary - other than to provide equal load in both sides of the drive at the head.
__________________
Two roads diverged in a wood, and / I took the one less traveled by, and / now where the hell am I?

This isn't a "you're doing it wrong" topic. (Originally Posted by Human Ills, 7/1/14)
Wadester is offline   Reply With Quote
Old 04-01-2013, 02:11 PM   #818
HeatXfer
Bad knees
 
HeatXfer's Avatar
 
Joined: Feb 2008
Location: S.F. Bay Area
Oddometer: 623
Quote:
Originally Posted by Wadester View Post
Torque steer is the issue - but the place it would come from would be at the headstock. If you have a single drive, it would certainly want to turn/steer in reaction to torque applied - just like the rear swingarm wants to extend downward when you apply torque.

Driving both sides of the hub is not completely necessary - other than to provide equal load in both sides of the drive at the head.
Thanks Wadester, that was the same conclusion I came to after reading both references. I realized neither addressed my question clearly. Originally my attention was on the wheel, not the steering head. I've got a thick skull.
HeatXfer is offline   Reply With Quote
Old 04-01-2013, 02:17 PM   #819
CosentinoEngineering
Gnarly Adventurer
 
Joined: Oct 2010
Location: NYC
Oddometer: 183
Wadester has it right, its the bevel drive in the headstock that needs to be balanced. There are only dual driveshafts because you need opposing torques in the headstock.

In the headstock one end of the drive is anchored to the frame the other end is anchored to the triple champs. If it was only a single bevel drive then as soon as the front wheel drive system was loaded the steering would want to turn to the stop. This wouldn't be torque steer in the conventional sense as that is a small side effect where this is using all of the engine torque to turn the steering. Once the steering hit the lock then the front wheel would start to spin. Not a good design.

Christini's dual bevel drive and telescoping drive shafts allow the triple clamp assembly to 'float' on the opposing torques. By having a top and a bottom output bevel gear the system is torque neutral on the steering axis and then by having the bevel drive on the fork lowers be mirror images the reversing torques are resolved to be all in one direction. Christini recommend that a steering damper is not needed so I suspect the added torques in the steering system create a damping action of its own which in this case is a benefit.
__________________
Chris
moto2-usa.blogspot.com
Check out my products 10% off for ADV rider members
CosentinoEngineering is offline   Reply With Quote
Old 04-01-2013, 03:15 PM   #820
Orangecicle
Beastly Adventurer
 
Orangecicle's Avatar
 
Joined: Apr 2007
Location: West Des Moines, IA
Oddometer: 2,336
Torque


Torque can do some funny things.
__________________
"I'd like to meet the joker who had the nerve to call this a road!" -- Walter Sigmann
"Gravity is a very fickle mistress." -- Unknown
Facebook Page: https://www.facebook.com/brad.horn.9
Orangecicle is online now   Reply With Quote
Old 04-01-2013, 03:49 PM   #821
DRjoe
Beastly Adventurer
 
DRjoe's Avatar
 
Joined: Sep 2007
Location: Sunshine coast qld
Oddometer: 5,020
Ha
DRjoe is offline   Reply With Quote
Old 04-01-2013, 04:26 PM   #822
sakurama OP
on an endless build
 
sakurama's Avatar
 
Joined: Oct 2004
Location: NYC & PDX
Oddometer: 1,431
Quote:
Originally Posted by CosentinoEngineering View Post
Wadester has it right, its the bevel drive in the headstock that needs to be balanced. There are only dual driveshafts because you need opposing torques in the headstock.
Thanks Chris. I'm going to miss having you right next door. Being wrong from the other side of the country isn't nearly as much fun as being wrong right there where I get the eye roll and the sardonic, "Well think about it for a minute." You need your own emoticon.

As an aside I finally got the boxer to idle today - only took 10 years...

Gregor
sakurama is offline   Reply With Quote
Old 04-01-2013, 06:07 PM   #823
mookymoo
Mookish Mook
 
Joined: Aug 2007
Location: Either UK or Australia ...
Oddometer: 4,387
Quote:
Originally Posted by CosentinoEngineering View Post
I only hope the weather is still cold enough to test cold starting.
Do you have access to a big cool-room?
mookymoo is offline   Reply With Quote
Old 04-02-2013, 11:05 AM   #824
ramon
weezin' the juice!
 
ramon's Avatar
 
Joined: Sep 2002
Location: California
Oddometer: 1,118
Awesome project!!
__________________
"...if you don't like the price then move on because I don't give a shit...it's my bike and I will sell it for whatever I want." Craigslist SF posting
ramon is offline   Reply With Quote
Old 04-03-2013, 09:26 PM   #825
CosentinoEngineering
Gnarly Adventurer
 
Joined: Oct 2010
Location: NYC
Oddometer: 183
>>Being wrong from the other side of the country isn't nearly as much fun as being wrong right there where I get the eye roll and the sardonic

Isn't that what facetime is for?
__________________
Chris
moto2-usa.blogspot.com
Check out my products 10% off for ADV rider members
CosentinoEngineering is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
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 On

Forum Jump


Times are GMT -7.   It's 05:44 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014