Wondering if anyone may have some input on what they feel may be the advatages or disadvatages of the sidecar swingarm being a leading or a trailing arm (meaning the pivot point is in the rear or in the front).
I will be building a new chassis this winter and am leaning toward pivoting the swingarm in the rear.
Any and all input appreciated,
Posted 11/8/2003 11:20 AM (#1474 - in reply to #1457) Subject: RE: Sidecar Swingarm question
Location: Boise, Idaho
I can't think of any distinct changes in geometry regarding leading vs trailing link suspension. The one advantage of trailing link is that it allows one to place the S/C tire further back which enhances slow speed steering. And nose dip, I might add. PM Dave, any theories here?
Posted 11/8/2003 3:14 PM (#1477 - in reply to #1457) Subject: RE: Sidecar Swingarm question
Just to confuse the issue, what about having the pivot sideways like on the EML's............The swingarm pivots near the bike side of the frame, so as the rig leans while cornering the sidecar wheel is still flat on the ground. They claim it helps stabilize the rig in left handers. (or they did, haven't been able to get to their web site lately so not sure what's going on with them)
Posted 11/8/2003 4:15 PM (#1482 - in reply to #1457) Subject: RE: Sidecar Swingarm question
Location: Boise, Idaho
Don't forget Harley's state of the art suspension innovation for the last century. None at all. Heh Heh.
Posted 11/8/2003 7:10 PM (#1485 - in reply to #1457) Subject: RE: Sidecar Swingarm question
Trailing link has the advantage of the impact forces on the wheel reliably compressing suspension. With a leading link, the position of the swingarm pivot in relation to the axle determines whether the suspension wants to extend or compress when the wheel hits a bump. Whether leading or trailing, compression or extension of the suspension causes a similar change in trail.
If you remember the Gelbke Auto Four motorcycle, based on an automobile engine. (You've probably seen a photo of this monster, 17 feet long as I recall, with Bill Gelbke smiling from the saddle) The Auto Four had a trailing link front end, with multiple shock/springs. My point is, a trailing link requires the downtubes to stick way out in front. A leading link allows the downtubes to be tucked in closer to the bike.
If you're designing your own sidecar front end, why not do a hub center steering? (that's "hub centre" for you Brits) One big advantage of hub center pivot is that you can have "automobile" like caster by inclining the king pin at an appropriate angle, rather than having to work around motorcycle rake angle. All you have to do is figure out a way to support both ends of the kingpin entirely inside the front wheel hub. I'm not sure if the kingpin can be to either side of center, but I suspect it needs to be very close to the bike centerline. I've never built a hub center front end myself.
The BMW "oilhead"/Armec Tremola rig I tested a few years ago had an interesting front end, sort of "hub center" with the upper suspension carried on the BMW Telelever A arm, and the bottom carried on a horizontal A arm pivoting "sideways" from the sidecar frame. It worked very nicely. I also did a test ride on the (then $60k) GG Duetto. It was great at higher speeds, but very combersome at slower speeds. The Armec site might have detail pictures of their front end.
However, I continue to lean toward a "conventional" leading link front end, which allows much greater latitude in selection of rims, brakes, etc. It's definitely preferable to have floating brake calipers linked to the downtubes rather than to the swing arm. And if I were building a sidecar front end today, I'd be thinking about some sturdy method of adjusting trail on the go. (say rotating eccentric swingarm pivot bearings, like those used to adjust rear axle position on some chain driven bikes. Of course, I'd like mine to be power driven so I could adjust trail while motoring along.
Posted 11/8/2003 11:38 PM (#1497 - in reply to #1485) Subject: RE: Sidecar Swingarm question
Location: Middleburg, Pa
Well Dave I appreciated your input. Yes,I have seen the GELBKE machine. Called 'Road Hog' I think. It was on display at Vintage Days in Ohio a coulple years back. i think Buzz Walneck owns it still today.
The GG DEUTTO you mentioned, if I recall, had a link connected to the front spindle that looked like it was , or could have been, designed to serve two purposes. It appeared to be a trail (castor) adjustment and also a link that would maintain consistant castor throughout bump and rebound of the front wheel. Pretty ingenious I felt.There is a picture of one on the internet somewhere.
Anyhow...as much as I would like to discuss center hub steering and the like my original question did not pertain to the bike but to the sidecar itself.
One sidecar frame I will be building over the winter is destined for our K100 bike. The suspension will be a cross torsion bar (perpendicular to bike)for the sidecar and another for the rear swingarm of the bike. I have been thinking of pivoting the sidecar swingarm off of the rear of the sidecar frame. The torsion bar will be mountd in a structural crossmember tube (1 1/2" .120 wall D.O.M.)and will also be the pIvot for the swingarm. This seems like it will 'clean up' the forward portion of the frame somewhat to allow for another cross wise mounted torsion bar to act as the suspension for the motorcycle. Both of these bars can be loaded or unloaded via two very simple master/slave cylinder devices for full 'on the go' adjustment. There will be another torsion bar connecting these bars that will act as an anti-swaybar. The whole thing is a lot simplier than I am making it sound here.
So my question was.. what, if any, pros or cons are felt to be related to the position of the sidecar swingarm pivot point...Front - vs - rear of the sidecar tire?
Oh..Lonnie I do have another project underway that does have a rigid Sidecar suspension. It has adjustable lead and toe-in at the sidecar wheel. That one has a torsion bar suspension on the rear of the bike too. Kinda goofy but fun to build. Hopefully both of these rigs will be done before spring.
Edited by claude #3563 11/8/2003 11:47 PM
Posted 12/12/2003 11:23 PM (#1759 - in reply to #1457) Subject: RE: Sidecar Swingarm question
I haven't built any sidecar chassis yet, but I have built quite a few street rods. If you know what a slack adjuster from a air brake system is I have some good (in my opinion) ideas and experince in using them in infinently adjustable suspension, especially torsion bar. Mopar of the 70's&80's midsize cars had the bars running fore and aft and might work quite well for sidecar chassis building. Let know if I can help further.
Posted 12/15/2003 6:08 PM (#1769 - in reply to #1759) Subject: RE: Sidecar Swingarm question
Location: Middleburg, Pa
Intersting about a slack adjuster and have toyed with the thought of using one myself for different applications. I can see how it would maybe have some potential. Please post or email me at firstname.lastname@example.org.