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Discussion in 'Hacks' started by High Octane, Jul 8, 2015.
I did just talk to my financial planner and gave myself a raise. I’ll call you next week.
Where is Luke when I need him!
By the by SWMBO says she’s up for a OZ sidecar vacation. !!!!!!
West coast is awesome.
Some accomodation available by the sea.
A lap is only 10,000 miles.
Lengthening the swingarm to decrease trail some more ?
Chopping up the finely made Euro S/A is a bold move. But , you make a lot of bold moves.
I thought for two days before doing this. My trail with the small moto wheel is 1 7/8” and with the big wheel is 2 7/8”. And 1” more in the second position. Both wheels are drivable, the small moto wheel better but I do prefer a quicker steering rig. The moto tire is almost there, but not quite. I did consider making a leading leg type of bolt on extender but decided to just do a tube extension instead. I considered threading the extension so it would be adjustable and then I could dial it in perfectly. But the threads would always be weaker and worry me. I’m thinking about modifying the pivot to make that adjustable. Similar to a chain adjuster or maybe an eccentric. Dunno yet.
If it all turns to crap a new swing arm really isn’t that hard to build.
I need to get this all sorted before I lock in on some new shocks as the length will change. The leverage will also change some but I don’t know if it’s a big factor or not
Effective spring rate changes to the square of the leverage ratio, so a 10% change in leverage will mean a 21% change in effective spring rate, a 5% change will alter the spring 10%. Also the angle of the shock matters (use the cosine of the angle from vertical.
Effective spring rate = (actual spring rate * cosine shock angle) / (leverage ratio)^2
and I have no idea how you would represent that in RPN
I really like the usage of plug welds to strengthen the joints. Personally I wound put a short section of the larger tube in the middle of your extension. Leave just enough gap so you can "burn a root" making sure you get full penetration down to the extension. That would help eliminate stress risers at those points. But if that is a solid rod and not a smaller diameter tube that wouldn't be needed.
God I hate powder coating! If you are going to TIG weld it I would sand it back further from the weld joints so the burning power fumes doesn't contaminate the weld which can produce porosity in the weld. MIG welding it isn't as big of an issue.
OK now for the rest of the story, I believe both Doublemocha and twintwin got another swingarm from EZS as they weren't happy with trail, probably because they where designed to run with 145/65/15 or 175/55/15 both considerably shorter than what you all wanted to run.
Larger tire patches heavier steering never mind the trail figures.
Now Octane with all the humility I can muster (not much) build the kind of sidecar you want ! At the rate your proceeding a Dedome moded telelever would have served you just as well (allot cheaper) and if you really wanted a welding project why not move the chair swingarm mount to the bottom of the frame to get it up where it belongs ?
I'm the guy who off pavements a road rig chair height helps, I've been hung up sidecar frame more than once.
Just like you I've spent too much time and money figuring out what works for me.
I'm currently a road dog I like the big front tire contact patch as most of the time I'm on pavement.
Of course I'm out of line as I'm superimposing my values on poor Octane
No guts no glory!
More to come.
Ah! TIG welded!! Nicely done, looks great!
I put a couple small welds in, then took it for a ride. It’s pretty damn nice. The small moto tire in the max trail position and if I have my calculations correct the big tire in the minimum trail position should be about right too.
Now to take it apart one more time and weld it out.
I’m sure if I went with one of those Dedome tele gadgets I would have still cut it apart and welded it back together!
Believe me I’ve thought more than once about cutting into the DMC chassis. I even bought swing arm steel. But then I think it would be almost easier just to make an entire new chassis rather than, raise, swing arm, anti sway bar, electric lean,... And I figure if I do make a new chassis the DMC one would be worth more if I just left it un molested. But so far I’m just enjoying the handling of it as it sets.
Finished welding the internal parts then slid the sleeves over it and welded things up water tight. Looks plenty strong to me.
I bought some stainless steel to remake my axel spacers. Once that’s done I plan to take it for a ride in the minimum trail position. Assuming I live through that I’ll put it where I like it best and be done. Except for the eventual powder coat.
All is good. I put the swing arm in the minimum trail position figuring that the trail would be to little.
But I rode all day and I like it very much.
I’ve been thinking that since I didn’t relocate the shock mounts I likely didn’t get the full effect of lengthening the swing arm.
But I like the end result. Perfect. For me anyway.
The leverage of the overhang from shock to axle would be reduced due to the increased length of swingarm between pivot and shock?
I:E stiffen the ride marginally.
The increased angle of the shock though would soften the ride a little?
So the difference would mainly be in the reduced steering effort?
Others mention things like trigonometry and other calcumalations.
It would be interesting to see if there's more shock travel, as I've found with mine one can notice changes in preload and damping but the shocks never use their complete range of travel.
Would of you real engineers know why ?
I need to redo all my shock travel dimensions and such after changing the swing arm anyway. So I should have some numbers for you. All I know right now is I used about 1 1/4 inches of travel in the front yesterday while testing things.
I suspect that the reason you (and likely I) don’t use all the travel is that we don’t set our rigs up with a lot of sag. While discussing my rear suspension set up with Jeff at The Beemer Shop he didn’t like my 10mm sag at all. It doesn’t allow for the shock/wheel to extent into pot holes. So I put it back to 63mm sag. I haven’t checked the rear but I obviously will be using a different section of the stroke, and maybe more if I hit pot holes.
I’m no suspension engineer but I would think using more travel would require more bumps! Or softer springs.
Bigger bumps at higher speeds or higher jumps should do it.
Or do you want the full geek out.