Sidecar Design Formula - IMPORTANT!

I have a selection of test springs with known weights. When I say selection, I mean 3.

If I'm building an outfit that is different to others I have done, I'll pick the one I think is right and try it.

If it's too soft, harder spring.

If it's too hard, guess what?

Springs are cheap, if you build outfits or mess about with them a lot, it's a worthy investment and you can guage the exact spring that you want from the 3, rather tha ending up with something that is what someone else used, but isn't really quite what suits you.

As the man said, Hagons are fantastically helpful and knowledgeable people, give them a call.

Re width, if it is to narrow the rig will be easier to tip over, the wider you go the more stable it will be.

Re Springs. Approach the factory that makes the springs for Alf Hagon, I cannot remember the name, but they are in Indian Queens in Cornwall, just off the A30. I will make a couple of phone calls and see if I can find the firms name.

European springs and pressings, they have a downloadable catalogue and here is the link

http://www.europeansprings.com/

Phone 02086 631 800 (+44 2086 631 800 for the foreigners)

That is the London number

Here is the Cornish number 01726 861 444

Track width seems to be not so much an issue of wb/track/lead percentages, more like whatever works on the trails you'll be riding, tracks to follow, etc?

This should be easier than trying to fit to an ideal, since I can now design to what payloads and roads work for me!
Thanks!

Thanks for contributions so far.

Investigations and advice from elsewhere indicates it's not simply down to spring rates, but that the damping ability of a coil over unit has to be considered. Springs overwhelming a unit's ability to correctly damp the spring's reaction has to be borne in mind. The damper has its limits, which I appreciate. Other factors are the varied modes of use imposed on our outfit - passenger in the sidecar (with and without luggage), sidecar full of camping gear and pillion passenger, even the latter set up plus towing a teardrop camping trailer. Compromise isn't the word.

I appreciate that if an outfit follows something of a norm, e.g. Beemer GS and single seat sports chair, there's likely to be a unit specification that can come off the shelf. Difficulties arise when the outfit is a bit different and doesn't follow a norm, which is the case for me. Still, part of the fun really.

The desire is not to waste limited finances on yet another suck it and see approach. I have a shed full of parts of all descriptions that didn't quite perform and have had to be replaced quite soon after. Possibly goes with the sidecar game. Important thing is not to tell the missus of such spending miscalculations for fear of reprisals.

I hope to be getting closer making a decision, having spent some time doing the maths, browsed the internet, and taken advice. However, more advice and thoughts still welcome because it might help others.

I put an adjustable torsion bar rear suspension on my old K100 outfit., Not talking antiswaybar here. Worked good.

Even with the shock you have ,if it isn't totally trashed; the addition of an antiswaybar would make a lot of diference.

Claude,
Had serious thoughts about a sway bar, but puzzled with how to attach on a single side swingarm as on our K. Problem being that the sidecar is on the left of the bike.
Makes me wonder if any of our Aussie boys have gone that route seeing as they have their sidecars mounted same as the UK ?

You can run the bar all the way across and attache to the 'non sidecar side' of the outfit..
As far as the discussion on spring rates go there are so many variables with a sidecar outfit it is virtually impossibe to make any blanket statements. Effective dynamic spring / shock combinations are what counts. What works on one outfot may not be ideal for another.

Agent Wayward alluded to trial and error as a means to begin and possibly improve things.( If I'm building an outfit that is different to others I have done, I'll pick the one I think is right and try it. If it's too soft, harder spring. If it's too hard, guess what? )

Not far off base me thinks.

Shock angles come into play as does where the shock is mounted on the swingarm in relation to the swingarm pivot point and the sidecar axle itself. Weight of the outfit, track width, swaybar or not, wheel lead, what the suspension is on the bike, shaft or chain drive, blah balh could all be factors that affect things. Yes, some enginner types may come up
with the 'ideal shock.spring combination' but even at that there is always room for improvement.

Shock valving also is a factor of course.

We typically run a 170/ 240 spring rate on the dual sport type outfits with a swaybar. On heavier sidecars we go to a heavier spring. Shocks moutned behind the sidecar axle will get more action that those in front of the axle.Shocks laid down more will seem softer. Shock angles can do weird things to how a shocks spring rate increases during bump.

Sidecar suspesnions are notorious to have very little sag set into them. Check that out sometime.

Multi track vehicles and even moreso non symetrical sidecar outfits are challenged by things, suspension wise, that a solo bike isn't dealing with. Dynamic weigth transfers in left and right turns, The center of mass working through a ground level roll center, High center of gravity, and so on.

The spring rates of the swaybars will vary depending upon the length of the bar. The dynamic 'working' spring rate of the swaybar will vary depending upon the arm lengths, the angle of the arms etc..Short arms may work well with a soft bar whereas longer arms may cry for a stiffer bar to acheive the same overall results.

Lots of stuff to think about. The voices in one's head can get quite loud sometimes lol. Sorry for rambling:eek1

Claude,

You don't ramble !

Your comments about the sway bar approach has had me going over the various sway bar information contained on ADV. Allied to past discussions with others, I can see this is a way to go, so the tape measure is back out, plus a look at some possible auto stuff.

Clearly, still require an uprated suspension unit for the bike's rear end and this is now being worked out.

I made 2 satisfactory sidecars before but finally I made one which refused to work because it was too light [ about 20 lbs] no missprint, it was that light. I made an articulated sidecar of it and was amazed....it was so much better. The motorcycle still functions as a motorcycle rather than being like a very fast tiller steered riding lawnmower. If you are going to the trouble of making a rig, consider a leaner, you will never go back.

Wow I am glad I am doing my research. I see I can buy a frame for 1200 US +shipping. but I am a fabricator so should be able to build one for less . But I need the info about how it will change the balance and steering of my bike. A DR 650 . with all the good stuff here I should be able to wade into this project with no real issues . If this goes ahead I will take pics,vids and post end results. if anyone has really good leads info I will accept all info in a PM onto the winter build season . but as I live in Victoria winter is more of an extended fall rain squall season.

read these threads

http://www.advrider.com/forums/showthread.php?t=571308

http://www.advrider.com/forums/showthread.php?t=691705

I'm at the end of a DR650 project myself - the above two threads were priceless and boxertwin is very helpful.

Started reading, 5 pages in so far, it would be 2 pages if you took out all the shit fights...
Back to page 6.

it was discussed some earlier in the tread. how much lean in on the sc wheel is appropriate? is there any drawbacks?

You want the side car wheel (tire) to toe in and the bike to lean out (away from the sidecar).

I have read that most people use about 3/4" of toe in and about 3 degrees of lean out.

FYI, I have a 57" wheel base and about 10" of wheel lead.

When I set mine up, that's what I started with. It was a great starting point. I ended up having to lean mine out more so it would track straight - maybe about 5 degrees. I also later adjusted mine to a little less toe in, but believe I will have to go back to about 3/4" as I now get a bit of wobble (head shake) where I did not previously.

The drawback with "lean in" on the bike is that it will always want to turn right - you'll end up fighting it.

The drawback with "toe out" is very unstable and dangerous steering. The bike wants to crab down the road.

Good luck!!!!!

If you are truly referring to sidecar wheel lean in - mine doesn't ave any. Those that I have seen, have no lean in. Though I have seen motocross bikes on line that have a huge amount of sidecar wheel lean in.

no I mean lean in on the sc wheel, found this on page 10 but but maby I missunderstod.

>>one trim setting that is largely ignored is chair wheel "camber". Lean-out is a camber adjustment to balance the drag of the chair. Chair wheel camber can help too. Chair wheel lean-in can reduce toe-in and lean-out requirements. With lean-out, the camber hurts turns into the chair, you would like to have lean-in. With chair wheel lean-in the driving and steering wheels are more upright for turns into the chair the lean-in is "good" camber for turns away from the chair.<<

I know you're new around here and I don't want to chase you off in any way. Unless you use the proper term of 'Camber' instead of 'Lean' nobody is going to know what you're talking about, because Lean isn't Camber and Camber isn't Lean. Proper terminology helps everybody including you and incorrect terminology can make a real mess of things. Of course it's not just you by any means! One of my pet peeves though...

I know that all these different terms can be real confusing and I'm just learning myself, so hang in there, it starts to make sense after awhile....

thanks for the comment. I mean negative camber on the sc wheel.

I normaly have problems expressing my sely clearly doing small talking with my wife. being clear about technical stuff in english to people on another continent is bound to be a problem.

Hey, wives don't count! I'm convinced they're not just from another continent, they're from a different planet.

Sorry if I sounded harsh. You have a good excuse but with some people it's just pure lazy, "You do my thinking for me, okay?" NO, it's NOT okay :ddog

Hope the best to you with your sidecar/hack adventures!

I built my own sidecar from scratch and I decided a prerequisite was a fully adjustable sidecar suspension, camber and toe in. Not extremely difficult to implement and very advantageous.
Just attach the car fundamentally, set basic toe in and camber, road test, pull over, make quick adjustments, proceed.
No need to adjust the entire rig in order to track properly.