Ok, I am hoping to tap the combined wisdom of the group here...
I am currently setting up my newer Champion Escort (2003 model) on my R100RT. I have a three-point subframe which is very solid that I have been using with my old HitchHiker.
the subframe is set up with ball mounts at the front and rear lower mounts, and an eye up near the battery box, just below the seat. With the HitchHiker it allowed the upper strut that attached there to be practically perpendicular to the axis of the bike/car, and came into the frame of the chair about 2/3 of the way back between the two slide clamps.
I found this to be very nicely triangulated and plenty stiff without the need for a forward upper strut. I never had any problem with the mounts shifting, flex between the bike and chair, tire wear issues, etc... And I am a relatively agressive rider...
My question concerns the setup with the new Escort.
Is the Escort all that much heavier than a HitchHiker that I will now notice the lack of the forward upper strut? Which motion/stress does that strut really prevent/protect against?
I do know that there are a couple of chairs out there that were designed with a single upper strut, like the Terraplane. Have others done the same with "traditional" sidecar frames? What has been your experience?
In looking at it while I have the fairing off for the setup and some other maintenance, I can see how to fairly easily fabricate a mount for the upper front frame location, but would really rather not go chopping holes in the fairing panel if it is not needed...
What is the collective voice of the setup/tuning gurus???
Thanks in advance for your advise!
hi, Karl,
I also had a terraplane with the single upper rear strut[adjustable] and no front upper one. no problems at all, but.... it had me worried..depending only on the single lower front mount bolt.If that bolt broke...woooooo! instant trouble!!
Add the upper front mount for more strength and ease of mind.
put the hole in the lower fairing part. you will be leaving the SC on the bike anyway.
If you sell the bike you, or the next owner, can always get a replacement lower for it.
Just a thought here, with my Honda GL650/Dneper that I have been abusing on the dirt roads in Idaho. I don't know how many of the 40,000 miles this bike had with a sidecar, but I broke the lower rear mount on a 4 hour ride to Boise. I didn't discover the problem till I got there. It was after hours and the welding shops were closed and my welder was 2 1/2 hours away. I took a chance and took 2 ratchet straps that were rated at 1000 lbs each and pulled the broken ends back together. The rear diagonal brace kept the broken frame from moving up and down and the straps kept the frame from moving left and right. I made it home on paved roads without further incident. I had the frame welded up the next morning. If it had been a 3 point mount, I would no doubt be stuck out in the boondocks or worse, upside down in a ditch.
Originally written by Mark in Idaho on 11/4/2006 5:13 PM
Just a thought here, with my Honda GL650/Dneper that I have been abusing on the dirt roads in Idaho. I don't know how many of the 40,000 miles this bike had with a sidecar, but I broke the lower rear mount on a 4 hour ride to Boise. I didn't discover the problem till I got there. It was after hours and the welding shops were closed and my welder was 2 1/2 hours away. I took a chance and took 2 ratchet straps that were rated at 1000 lbs each and pulled the broken ends back together. The rear diagonal brace kept the broken frame from moving up and down and the straps kept the frame from moving left and right. I made it home on paved roads without further incident. I had the frame welded up the next morning. If it had been a 3 point mount, I would no doubt be stuck out in the boondocks or worse, upside down in a ditch.
I'm with Mark on this. I broke a front lower mount on my old GL1200/HitchHiker rig and was able to nurse it home. Just like Dollars and Schnapps, More is usually better.
If you peruse the Vetter (and subsequent Terraplane) frames you may notice the rigidity due to the triangulation of the integral roll bar (that the adjustable rear upper mount attaches to). This rigidity is not available with a flat perimeter frame design. A third dimension must be present.
Lonnie
Originally written by Hack'n on 11/4/2006 10:23 PM
If you peruse the Vetter (and subsequent Terraplane) frames you may notice the rigidity due to the triangulation of the integral roll bar (that the adjustable rear upper mount attaches to). This rigidity is not available with a flat perimeter frame design. A third dimension must be present.
Lonnie
yes, but that still wont prevent the front from dropping to the ground if the front mount breaks. leaving only the rear upper and lower holding the SC to the bike.it will also spread apart , away from the bike.
thats like pulling a trailer with no safety chains..if the hitch breaks the tongue will hit the ground. the upper front mount acts like a safety chain in an emergency.
broken mounts?? check the lable, maybe made in china
I would go with four mounts. More mounts if done properly mean more 'shared' load .... structurally there is no negatives to this .
The only reason to run a single mount at the top if if someone wants a true lean adjustor. That is what Vetter did and others for a while . Today there are no true lean adjustors on the market that I am aware of. Everyone has gone to a system that tilts the whole rig instead of leaning the bike away from the sidecar. This allows the use of four mounts.
More is good. Overkill is good . Less may work and work well but why take the chance?
One solution I had been thinking seriously about with my Ex-terraplane, was to add a safety chain to the front pylon and around the bike frame somehow, making sure the chain is short enough to keep the SC front off the ground if a faiure occurs. like a trailer tongue safety chain.
I really liked the manual lean adjuster on it.
And strut or mount failure can create a potentially dangerous situation. If a rig has a single upper strut that fails in any way can be disasterous.
Think of it happening in a turn. Think of it happening in a left turn.
Maybe something like 2 trailer tongue jacks could be modified for a tilt feature.
Originally written by Mark in Idaho on 11/5/2006 9:42 AM
Maybe something like 2 trailer tongue jacks could be modified for a tilt feature.
When I was running my HitchHiker I was seriously considering/designing a linear actuator mechanism to replace the single strut. 12v linear actuators use a worm drive, so the gear train self-locks when not powered to prevent slipping, and you can tune the speed of motion with resistors or a voltage regulator circuit.
Done properly with heim joints below you could even lean it into the curves...
I just had too many other projects, and now have a girlfriend who is insane enough to enjoy riding with me in the winter months, so I found a nicer chair for her to sit in... 🙂
If it wasn't for her, the HitchHiker would still be in service with me for many more years...
btw - Using two linear actuators would not work well because of problems with syncronizing the rate of motion. If they don't move at the same rate they will bind up. AND, most times the struts are not parallel to each other, opening up a whole can-o-worms trying to get everything to move together...
See.... I knew I could get people talking... 😉
In general, yes, I agree with overdesigning. Within limits...
One area of design that is sadly neglected by many home workshop mechanics is fatigue failure and its various modes.
I look at LOTS of failed parts and very often I see signs of fatigue.
One of the best ways to prevent a catastrophic failure while enroute is routine maintenance, detailed cleaning, and INSPECTION!!!
Look for signs of minute cracks forming, slight deformation in mating surfaces, crazing/cracking of paint...
Also, when designing your mounts, avoid if at all possible sharp bends, notches, etc. in your parts.
Make sure that all threaded fasteners are loaded in pure tension. A thread is about one of the most fatigue prone shapes there is because of the deep, sharp groove running down its length. Putting repeated bending stress on that grooved shaft will snap it FAST.
Also poor quality welds are a BIG cause of fatigue failure. If there are pits, undercutting, inclusions, etc you are creating HUGE stress risers. You don't just grind out/file welds smooth to make them pretty, it reduces stress at the joint to have a smooth transition fillet.
Steel is actually pretty forgiving, and if designed properly will warn you it is in trouble long before it gives up the ghost.
The BEST advise is to keep the mounts clean and inspect them regularly. You can't see cracking starting through dirt and grime.
IMHO
I am an artist, not an engineer. I do a lot of this stuff by the seat of my pants. In a close tolerance system, the binding would indeed be an issue. I was instead thinking that 2 diagonal braces could be adjusted alternately a little at a time. I was not considering trying to make the adjustments on the fly electrically. Your girlfriend sounds like a keeper.
In my experience you probably wont drop the nose if you bust a strut mount(presuming two good lower mounts with some distance between them).
What does happen is the leanout and toe in can change if you bust a mount. With a four point mount this usally shows up as a more or less gradual increase in steering effort, decrease in steering control and a wobble. I haven't experienced this as an undrivable or sudden change(with a four point mount)
I have ridden one, two and three point mounts that worked OK but my experience with them is very limited. You sure want those mounts to be stout and the attachment to be free of flex if you go with less than 4 points.I prefer 4 point mounts for the added rigidity-not just from the leverage of the mount and strut but also because the added mount tends to bind if there is movement due to flex or failure at another point.I have occasionally worked on 5 point or more mounts-they are harder to set up and don't seem to be worth the extra effort.
