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Need some engineering ideas for subframe

Posted: Wed Apr 22, 2009 10:20 am
by jaybob
Hey Guys. I have my subframe mostly built and seat pan fitted. Now what I need is some good engineering ideas on what to do for a strut to hold it up when filling the oil tank and to stop if from rotating too far when it is open.

What would be really neat is a small gas charged strut that when I unhook the front fastener it would automatically raise by itself. I've not rersearched my options there yet.

I would also like some alternative ideas. It does not have to open as far as the picture shows. Actually it should not to provide clearance for the tail light etc.... Just needs to open far enough to comfortably access the battery and oil tank.

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Posted: Wed Apr 22, 2009 12:23 pm
by Zook-e
Hopefully you won't activate that strut while riding. :shock:

Posted: Wed Apr 22, 2009 12:46 pm
by jaybob
If I got a strong enough strut I could market the idea as a last ditch crash avoidance device. Don't lay the bike down...Just eject!!!

Or better yet make a split two up seat so you could eject the passenger if she starts nagging too much!!

Gas shock, or cable

Posted: Wed Apr 22, 2009 1:02 pm
by krwalsh
If you want it to raise up after unlatching, what you are looking for is a gas shock. McMaster-Carr sells them, and has a mini-tutorial on how to use them. Try this link: http://www.mcmaster.com/#gas-shocks/=1k4hz6

IMO, a gas shock is overkill for what you're doing. But I can see the bling factor. You would want it to go over-center at the bottom so the gas shock actually keeps it closed. Then after you lift it a couple inches, it would push it up.

For me, I'd skip the gas shock and go with a cable attached to the frame and to the seat subframe to limit over-travel when it is open. That'sll keep it from going over backwards, and unless you have a wind, it will keep it from slamming on your hands while you're in there. Last thought is a simple prop rod, similar to a car hood prop. That would be simple, light, and keep it from going over backward or forward.

Posted: Wed Apr 22, 2009 1:23 pm
by jaybob
Yes I agree the prop rod seems to be the best choice especially since this is not super high dollar engineering masterpiece.

Posted: Wed Apr 22, 2009 8:24 pm
by diamondj
Dumb question on my part - where are the tail light & license plate going to go?

Posted: Wed Apr 22, 2009 8:34 pm
by tz375
Or go down to your local car wrecker and pull a gas strut off any old hatchback. It would be cheap but probably too strong for the application.

Or just go with the prop rod and cable so it doesn't get away from you and smash the tail light you are just about to fit.

Posted: Wed Apr 22, 2009 11:09 pm
by Buffalo-guy
It looks to me like you will have rear fender interference issues at even a small openning angle. This all presumes that there will be a fender. In that case, the pivot point may need to be moved further back on the seat. Maybe I'm wrong. Its been known to happen. Cheers.
Fred

Posted: Thu Apr 23, 2009 9:11 am
by jaybob
No Fender...Do I need a fender? Nah I retained the original inner fender and I plan on blocking off the underside of the tail to keep stuff from flying up inside it.

As for a tail light I have a few ideas, either will be frenched in or I have some custom bracketry in my head.

I think clearance will be fine as the tail only needs to open to about 45 degrees to comfortably access the oil tank and battery.

I appreciate the constructive criticism, it helps keep me on track. This excercise is more about style than practicality, but I understand I need both to have a well rounded package.

Posted: Thu Apr 23, 2009 1:14 pm
by tz375
Jason, when you said:
I have some custom bracketry in my head.

I did have to stop and wonder for a moment. :lol: :lol:

That's a better excuse than the rest of us came up with for the way we think. :roll:

Posted: Thu Apr 23, 2009 3:23 pm
by jaybob
That's right. I usually need something to "prop" up my ideas

Posted: Thu Apr 23, 2009 4:57 pm
by Suzukidave
The gas strut idea is funny as thats what i used to aid holding the gas tank up on the GTX-R . My son was replaceing the strits on his car as he had 1 bad one so he was just going to replace both . I was building this bike at the time and couldnt see throwing the good one away and it ended up being the perfect thing as it will lift the tank by itself and holds it up even if its full :D Image