Extension Suspension (an idea)

[John in CR]

It bugs me sometimes that my original ebike frame is collecting dust. It's a decent Trek hardtail, but because it's AL, I can't just cut it up and add pieces to transform it. If you weld on these heat treated frames you give up much of their strength. I need more than a granny ebike, so a hardtail is out of the question. Plus extending a bike can get you lower, more aero, and more stable at traffic speeds. I'd also like to see if I can keep this one pretty light, instead of my usual "A little more steel here and there won't hurt anything, since it has a motor and is lighter than a motorcycle."

What I'd like to do is just fabricate a lightweight swing arm with the pivot being a bike hub that I can connect directly to the existing rear dropout. It won't see extreme stress, because dual shocks will connect at or very near the rear wheel. I don't need much travel, just enough to smooth out road bumps.

Using a hardtail's rear dropouts as a pivot point for a wheelbase extension to turn it into a suspension bike seems no-brainer easy to me, but I haven't been able to find a single example to borrow ideas from.

 

[Toorbough ULL-Zeveigh]

trying out one of these on my oatnet TF frame that's slowly coming together.
$15 C/L item but needs to have much heavier springs made to replace the wimpy stock ones.
it's is an idea whose time has come & gone, plenty F/S to choose from nowdays.

 

[John in CR]

trying out one of these on my oatnet TF frame that's slowly coming together.
$15 C/L item but needs to have much heavier springs made to replace the wimpy stock ones.
it's is an idea whose time has come & gone, plenty F/S to choose from nowdays.

View attachment 1

Interesting gadget, however, I'd do the extension even if it remained a hardtail, but my back and ass say no. I do no trail riding, so the reduced danger of a longer wheelbase and lower seating are important to me at really no detriment. Plus I get real room for batteries and a couple of kids.

John

 

[amberwolf]

My CrazyBike started out doing exactly this kind of thing--simply adding a rear triangle to an existing bike frame, with the bottom bracket as the pivot (I just bolted the crankshaft to the dropouts). Then I couldn't find a good way to make a suspension spring out of anything I had, so I abandoned that part and went on to CrazyBike2 as a hardtail.
http://electricle.blogspot.com/2009/01/no-weld-semi-recumbent-idea-or.html

I later revived the idea to add to CrazyBike2 itself but have not yet gotten back to working it out due to the drivetrain problems with CB2 I need to resolve first.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=14570

 

[spinningmagnets]

I'm making a longtail out of a hardtail and a rear suspension arm. I'll have to fabricate an extension for the shock, but the rest should just drop in. Here's the longtail thread, and also the pic of oldhaqs bike that inspired me to try it out (not done yet, moving slowly)

http://endless-sphere.com/forums/viewtopic.php?f=1&t=9673&start=15

 

[John in CR]

Thanks Amber and Spinning Mags.

Amber, I thought about using a crank and just grind the shaft down to dropout size, and cut some threads. You gotta remember I'm the lazy type, so that's already done for me with a hub. Plus I think I gain a bit of advantage in terms of handling the lateral forces with the wider bearing placement on a hub. Lastly, in terms of ease for someone without welding capacity, there the option of picking up a front hub for double disc brakes and make the swing arm a bolt on.

Spinning Mags, thanks for the link. I knew I had seen one. I'm not sure how that guy pedals, but it's kinda the same track I'm on. Take his, forget the triangled swing arm, and put dual rear shocks running vertical from near the rear axle. Then imagine the space available. If I can find something really light for the shocks, maybe this is the one I try the ventilated Fusin geared hub, and go for a composite swing arm enabled by attaching the shocks directly at the rear axle. Then I could get away with a bit of aluminum plating at the wheel, motor mount, and hub to keep things really light weight. If the fusin blows apart, so what, I drop in the 2 speed tapped winding Xlite 4 series that's on the way after ventilating it, and I'll have a zippy lightweight cruiser surely capable of 4-6kw peaks and electronic 2 speed to boot.

Ok, thanks again. Thinking out loud moved this one up a notch or 2 on the list. Gotta get back to work on the 2wd monster, so LFP and I can try to break 70mph with a safe comfortable bike with passenger capacity. Kids just started back at school, so time for some new bikes to show off as a school taxi.

John

 

[spinningmagnets]

Whether one shock or two, I feel this is a great configuration for an urban commuter. I got a used Specialized 26" MTB hardtail at a very good price. It has front disc brakes and a strong but light aluminum frame.

I plan to use a 24" wheel and V-brake in the back, but even if I wanted to use a 20" wheel, I could easily index the suspension arm so that the pedals dont hit the ground. Plenty of room after conversion for a non-hub build of just about any type. Lots of options for battery placement.

 

[John in CR]

Whether one shock or two, I feel this is a great configuration for an urban commuter. I got a used Specialized 26" MTB hardtail at a very good price. It has front disc brakes and a strong but light aluminum frame.

I plan to use a 24" wheel and V-brake in the back, but even if I wanted to use a 20" wheel, I could easily index the suspension arm so that the pedals dont hit the ground. Plenty of room after conversion for a non-hub build of just about any type. Lots of options for battery placement.

I like it too. I lean toward 2 shocks for this specific build as support for the seating area for rider+passenger(s), the swing arm doesn't have to be designed for nearly the same kind of leveraged forces, and those mono-shocks are right where I want to put battery weight (protected, hidden, and low toward the rear).

 

[BLUESTREAK]

HEY JOHN: I just bought another schwinn meridian trike to use to make a extended rear suspension bike by using the frame of the trike and use the rear end of the trike to make into a trailer to be pulled by my big meridian trike. I bought a suspension steel frame from someone here on the sphere just to get the rear end off of to use on the meridian trike frame, I guess it will be a sort of xtracycle type with a rear end suspension, Iwill be using 1/4in steel plate to bolt the alum.trike frame to the steel rear end. right now i have too many projects going on and not too many completed.I am also making a trike rearend on a vectrix electric scooter. pictures coming eventually.

 

[John in CR]

HEY JOHN: I just bought another schwinn meridian trike to use to make a extended rear suspension bike by using the frame of the trike and use the rear end of the trike to make into a trailer to be pulled by my big meridian trike. I bought a suspension steel frame from someone here on the sphere just to get the rear end off of to use on the meridian trike frame, I guess it will be a sort of xtracycle type with a rear end suspension, Iwill be using 1/4in steel plate to bolt the alum.trike frame to the steel rear end. right now i have too many projects going on and not too many completed.I am also making a trike rearend on a vectrix electric scooter. pictures coming eventually.

Sounds cool. Don't forget to take pics during the process even if you wait to post them. I love seeing electric bikes and trikes that carry loads. I see it as a huge untapped market that even the motorcycle manufacturers have missed. The human power guys are doing the most, but introducing electric is a whole new ballgame and there's no reason to go all the way to something like a golf cart.

John