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9/17/2013 10:10 am  #1


MOTO GUZZI TRIKE SUSPENSION???

Hi, Ya'll...need some expertise.

I'm in the begging design stages of "wanting" to build a MG Trike using an EV 1100 Cal Special, ~75 HP, 70 ftlbs torque.  I want to use the existring frame, NO cutting/welding mods, and use existing mount points.  I want to be able to re-install the OEM swing arm, tire/wheel etc and sell it and use the trike portion to install on another motorcycle at a later date (maybe).  I also will put a "Pickup" bed, ~8" x 45" s 66" aluminum on it instead fo the usual fiber glass "coverall the ugly and make it kool" box.

I'm a weldor/mechanic by tradeamong other things, worked/built/fab'ed/etc a whole lot of "stuff" over some 60 years...BUT this is something new, I seemed to have "senior moments" crawling all over me and I'm asking questions, that are semingly obvious, on other forums, that are embarassing the H*** out of me when I get an answer.

First trike...want to use an IRS from some small vehicle that seem to be ubiquitous for cheap money all over the net.

PROBLEM:

The tranny output is offset to the right ~3".

QUESTION:

Just HOW many problems will I have in the roadability of the trike  if I offset the IRS 3" to the right of frame centerline so I will have a straight driveline?

The driveline will be ~18" long and a 3" offset equals ~9.5°  of articulation if the IRS is centered on the frame centerline instead of being offset... not enough to sweat...I will be using CV joints also.

QUESTION:

The machine is relatively low powered, WON'T be carrying much more than my fat little body and maybe 300 lbs max in the box which is below the stock GVW and WON'T be driven much over 65...as the speed limit in my state is 55 mph and I just DON'T drive fast anymore.

Any one have a suggestion/IRS specific love for which IRS brand to use.  I've looked at BMW, Jag, Subaru, CVR, Merkur, Supra, VW(latest models) andd many more inline, ebay etc.  I want the smallest, lightest I can get to fulfill the weight/usage specs.

I'vee been looking at many independent brabd IRS units for  various custom Harley, V8, Honda etc applications and many look massive enough to move a Abrams tank...and priced the same. 
And I've seem many complete IRS units for chump change...couple hundred bucks..WITH diff, brakes, axles AND shocks that are late enough models to not wonder about the longevity of the various parts.  Totally YOOGLY, but could be grafted on with a minimum of fuss, and painted over.

I want to keep my MG LIGHT, SAFE and USABLE.  I live in the boonies, 40 miles from town and the road is curvy, full of crazy drivers and crayzier deer/cows.

I built a side car for my '80 R65 Beemer and rode that util the bike finally layed down and sighed, then put it on the MG but the steering rake/trail on the MG  just wouldn't take the car and would tank slap at 20 mph.  I put on a steering stabalizer but that only solved the slap NOT the cause.  Bersides I'd really LIKE this MG so I want to make it and easy swapover from trike to cruiser and back again when the mood strikes(not sure if this can be done)

I got a bit wordy here hoping to cover most of the wondering about "What is he and what does he know".

I'm trying to get specific answers to specific questions that I will be asking over time.  I'm a rank beginner when it comes to IRS, Trikes, I have a home/garage metal shop, tons of tools, welding/cutting rigs and a fair amount of knowledg, but I need help in this endevor.

Thanks

 

9/17/2013 10:43 am  #2


Re: MOTO GUZZI TRIKE SUSPENSION???

First off welome aboard. Second, you don't have to offset the IRS. As long as the front and rear universals are at equal angle you won't get any vibration. Your not the first to ask here, seems there was a similar thread with the same question.

Day, maybe there ought to be a trike thread. LOL!

Ralphy

 

9/17/2013 1:37 pm  #3


Re: MOTO GUZZI TRIKE SUSPENSION???

Vibration wasn't the prime issue.  The diff and tranny will be square, paralllel, on center and plumb.  Offsetting the whole IRS setup 3" off center to the right is the main issue.  How will that affect steering, onroad tracking stability etc is my concern.  As long as the front/rear wheels are tracking perpendicular and parallel...what will happen when the whole IRS assy is 3" OFF CENTER when I'm moving down the road at speed, and how will the offset affect cornering.

     Thread Starter
 

9/17/2013 2:37 pm  #4


Re: MOTO GUZZI TRIKE SUSPENSION???

How great of an angle would the driveshaft be at a 3" offset? The only issue could be to much angle. Remember a IRS carrier is fixed to the frame There may be force off centerline, but again everythings fixed.

Last edited by Ralphy (9/17/2013 2:41 pm)

 

9/17/2013 4:47 pm  #5


Re: MOTO GUZZI TRIKE SUSPENSION???

I gave that in the first post...Formula is arc tan x (3 divided by distance between tranny and diff)) or arc sine x (3 divided by driveline length)...the articulation angle gets larger as the distances(driveline or unit separation) get shorter, but it runs between ~14° and ~9° for driveline length/unit distances of 12" to 19".  There isn't a whole lot of difference between a unit separation if 18" and the driveline length...the driveling lenght would be 18.25".

Hardly enough to worry about for a CV joint articulation useful angle of somerthing betwee 40° and 50°.

I need to get the offset question answere/solved before going much farther as this dictates the wheelbase and how/where the IRS is positioned.  I want the machine to be just "long enough" to give a nice stable ride and not "too short" to be squirrely in turning...whatever that happens to be???

I have to replace the MG's tranny rear seal which necessitates removing the rear wheel and swing arm.  I will measure the frame at that time, put the bike back together so I can ride it a while longer before winter sets in, acquire an IRS unit and start building the subframe and box frame this winter...hopefully.

Wheel width is determined by axle length and wishbone arm lengths which are variable and adjustable, made to order so to speak unless I happen to find pieces and parts that I can use.

Maybe I will get smart/lucky and find an IRS with a wheel width I can live with and not have to deal with trying to reinvent.

     Thread Starter
 

9/17/2013 5:08 pm  #6


Re: MOTO GUZZI TRIKE SUSPENSION???

WHERE/WHO/HOW can I get information on the black and blue IRS pictured in the upper right corner of the home page????

     Thread Starter
 

9/17/2013 6:43 pm  #7


Re: MOTO GUZZI TRIKE SUSPENSION???

So most or all cars have a built in angle but it's verticle. Why would any drive shaft angle in a horizontal plane make a difference? The trans and carrier are fixed solid. 

I saw err... read your post after the fact on the 9 degrees.

Ralphy

 

9/17/2013 7:25 pm  #8


Re: MOTO GUZZI TRIKE SUSPENSION???

Somehow my main question keeps getting missed...I say again, over...

What happens to the driving charicteristics of any IRS or solid axle vehicle when the WHOLE  member is shifted by 3" OFF the centerline????

Think about the rear end being 3 " out of alignment to the front end...3 inches offset keeping the axles square, parallel and perpendicular.  Just put a Z break in the middle of the vehicle or chop it in two just behind the front seats, slide the back portion to one side 3" and glue it back together...the azz end is offset to one side or the other doesn't really matter which side.  Looking at it from the rear the vehicle is going down the road with one end going along offset and both sets of wheels running in then same parallel plane but not running in the same tracks.

I know it would cause some kind of steering problems with 4 wheels, I'm trying to understand how MUCH of a problem will occure with 3 wheels.

Any information on the black and blue IRS on the right at the top of the page???

Thanks

Last edited by OLD-WAN (9/17/2013 7:27 pm)

     Thread Starter
 

9/17/2013 7:45 pm  #9


Re: MOTO GUZZI TRIKE SUSPENSION???

If you chose the blue Jag above, your going to have uneven camber curves, due to the fact your goingto have a 6 inch difference between the two sides. Weight bias may be off a bit.

Ralphy

Last edited by Ralphy (9/17/2013 7:49 pm)

 

9/18/2013 10:57 am  #10


Re: MOTO GUZZI TRIKE SUSPENSION???

I was just wondering what brand the IRS was.  I liked some of the design chareacteristics and it looks stought enough.

Where does the 6" difference come from???  The unit looks symetrical to me.  I thought it might have something to do with the Ford Mustang seeing the horses on it.

     Thread Starter
 

9/18/2013 11:17 am  #11


Re: MOTO GUZZI TRIKE SUSPENSION???

I was refering to your question, "What happens to the driving charicteristics of any IRS or solid axle vehicle when the WHOLE  member is shifted by 3" OFF the centerline????"

If you moved the differential over 3" on that Jag IRS, you'll have a 6" difference in half shaft and dog bone length. Causing an uneven camber curve.


Ralphy

 

9/18/2013 3:41 pm  #12


Re: MOTO GUZZI TRIKE SUSPENSION???

Missunderstanding again...I strived for clairity but didn't quite get there.  The question of offset is academic now and rendered moot.

I just wanted to know what vehicle that IRS came from as it has some pieces and parts that might prove useful...until I found what money was being talked about.  The design is still interesting.

I will use the "other" solution and center the IRS unit (unit refering to everything along the power transfer pathway...i.e. wheels, axles, differential, brakes, supports, wishbones, and shocks) along the frame centerline and offset the driveline.

Thanks

     Thread Starter
 

9/18/2013 5:21 pm  #13


Re: MOTO GUZZI TRIKE SUSPENSION???


You will notice I set the gearbox at a slight angle to the engine to help the rear drive shaft slide under the engine.
http://forum.difflock.com/viewtopic.php?t=14499&postdays=0&postorder=asc&start=570



Here's some info. Also let me say my engine/trans is offset app. 3/4" and no noticable issues.
http://www.hotrodders.com/forum/effects-offset-driveshaft-rear-suspension-geometry-115299.html

http://jniolon.clubfte.com/drivelinephasing/drivelinephasing.html


http://www.drivetrain.com/parts_catalog/drivetrain/driveline_angles_and_phasing_problems.html

Last edited by Ralphy (9/18/2013 5:59 pm)

 

9/18/2013 6:00 pm  #14


Re: MOTO GUZZI TRIKE SUSPENSION???

OLD-WAN said, "I just wanted to know what vehicle that IRS came from as it has some pieces and parts that might prove useful...until I found what money was being talked about.  The design is still interesting."


I also said the rear is a Jag more than once. Which type? Day and others can tell you. Day owns the board and it's his photo. Hope this helps.

Ralphy

Last edited by Ralphy (9/19/2013 3:11 am)

 

9/24/2013 2:42 am  #15


Re: MOTO GUZZI TRIKE SUSPENSION???

Useful information shared..Iam very happy to read this article..thanks for giving us nice information.
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9/24/2013 11:33 pm  #16


Re: MOTO GUZZI TRIKE SUSPENSION???

The black & blue at the top is Jag.
An excellent unit but pretty heavy for your purpose.

I would suggest BMW as it's very self contained in a cradle that is easy to remove.
This should ease your goal of being able to go back to two wheels.
The usual track is about 55" and the five lug bolt circle is virtually identical to a traditional Chevy.
Some are four lug, not sure if they may be lighter.
On a trike you want to avoid any model with a posi.
Pick & Pull sells them fairly cheap.
Guzzi and BMW seem a "Natural" combination. 

Mazda Miata might also be a good but I've had very little chance to examine them to see how they are set up.
Light car so the rear should be reasonably light too.

I would build the trike properly centered and just let the driveline be off-set.
Off center will take on some of the characteristics of a side hack, cornering in one direction will be stronger than the other.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
 

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