Ironhead Sidehack for XLS

[kitabel]

A multi-grade oil joke:
The 1st number (the "20" of 20W50) is the time in seconds for the oil to reach the last bearing in the engine.
20W50 = 20 seconds.

Unless your air temperature is 212 degrees (the temperature at which the "W" number is that weight), 50 or 60 weight is too thick to pass through the engine immediately.

[Ferrous Head]

I know that too little trail = tank slapper,

That one is a myth.

Fastest sidecars on the track are running ZERO trail. I am at one inch. (from memory).

One of the biggest problems with street derived hacks is the telescopic front forks. They really are just a pathetic design.

Reducing the trail too far on tele's increases the risk that the forks won't compress when you hit a big bump, but bend. (Well, they will bend anyway as they just aren't that strong but ...)

If you look at factory produced sidecars - BMW etc - they have leading links.

Years ago we ran super strong front fender mounts on our Superbikes. They weren't really fender mounts but fork braces. We called then that to circumvent the rules.

Consider anything to strengthen them. Tweak bars, larger diameter tubes etc.

[revjen45]

Thank you Ferrous Head.
So then would 1-2" of trail with a steering damper give lighter steering without instability?
I know that telescopic forks aren't the 1st choice for a hack, but I won't be driving it hard. It's for my wife and me to use for recreation. If something ugly befalls the forks I will replace them with something else, but right now that's more $ than I can spend unless failure necessitates replacement.

[kitabel]

Tony Foale tested a 2-wheeler with no rake angle at all, and found that trail alone makes the bike stable enough to ride across RR tracks no hands.

[revjen45]

I would be going the other way: 30.1 deg of rake with 1-2" of trail. Don't know how that would equate.
Also
2-wheeler and hack have different handling characteristics. How would that relate to a sidecar and how much difference would the steering damper make?
I just want to be sure that I don't do something that turns out not to work safely.

[Ferrous Head]

Like everything in life, it's a compromise.

Reducing the trail makes solo's and sidecars easier to turn. On a solo turning requires almost no effort. Anyone who understands countersteering can turn using dainty fingertips. precession takes care of the grunt work for you. But sidecars are different, cornering like a car.

It's all manageable with what your doing on the street. You may want to fit wider bars just to get some leverage.

The straight line stability comes from 'toe in". That needs to be set correctly. It doesn't take much though most will tell you 10 degrees. With zero toe in the bike will be unstable. Don't go too far though as this also "scrubs" the tire, wearing it out faster.

With zero trail the bike will become what I call "flighty", meaning any minor inputs to steering can have a larger than expected reaction.

Steering dampers a re a band aid approach to help with a problem. My advice is to fix the problem.

Single biggest source of tank slappers is loose/worn/damaged neck bearings. The steering head bearings handle the entire front end load. Those tiny little pushbike bearings have a line contact in the cups. The tapered Timkins are the much better choice here. But in any case, correct adjustment is critical for good handling.

Tire choice too is a big thing on sidecars. If you can find a flat profile tire that fits they are the absolute best option. They may look "funny" to most people's eyes, but try to imagine a set of Metzlers on a Formula one car.

You will learn what's required by riding it. The same as when you learned to ride a solo. There is an element of "balance" that is very useful on sidecars. Both you and your passenger should be shifting your weight into the turn. Takes time to learn how that affects handling but soon you'll be "dancing" as a team.

Have fun.

[revjen45]

I acquired new trees with 6 1/4 deg of offset and an adjustable damper, which makes all the difference in the world in terms of steering effort. Lead on the sidecar wheel is only ~3" which does not give good stability > 45-50 mph. I will be taking it into the shop to adjust this, which will hopefully give satisfactory stability at highway speed. We are looking forward to having it ready for the riding season. Will send pics when it's sorted out.