Four wheeled bike?

wvumtnbkr wrote: Sweet! I may have been speaking from personal experience. I have got my parents a kayak, bicycles, a wii console, anything to get them up and moving. Nothing works. I am glad that your Mom seems more athletic. Good for her! Silly question... Why not just weld two bicycles side by side. Like literally put them 2 feet apart and weld some tubes between them? The only thing to worry about then is steering. Use one of the handlebars to steer and hook up a linkage so it steers the other one as well. Am I missing something? Hell, you could even make a bench seat and pount it a little further back if you wanted something comfy-er

A few things.

I'd like them sitting further inboard for stability.

They may or may not be able to get over the top bar.

But you're on to the idea. I want to keep a lot of it the same.

Look for a couple of used Trek Navigators with the step through frame. They would be a nice option to design this around.

How are you at welding aluminum?

http://www.trekpunta.com/nav2wsd_archivos/navigator20wsd_black(1).jpg

wpcouch wrote: How are you at welding aluminum?

Uhh. "no"

Definitely only steel for this job. Good call, though.

Careful... Alot of steel bikes are chromoly. I believe you need to heat the material first before / during welding.

wvumtnbkr wrote: Careful... Alot of steel bikes are chromoly. I believe you need to heat the material first before / during welding.

hrm. When picking through junk piles, non-chrome moly would be super preferable. Any GRM easy way to tell?

In reply to tuna55:

Actually, a lot of them will actually say it somewhere on the frame. Quality/grade of frame material is often used as "marketing"

I wouldn't be to worried about the cromoly thing. We welded our fsae cars without preheat and never had issues. We would reheat with a torch to relieve stresses. I'm 100% confident we had more highly stressed joints than this would.

FYI Some vintage Schwinn Town & Country trikes have a true differential rear axle - albeit not one with LSD.

Also, I built a reverse-trike for a friend who has balance and health issues, and I've bought/sold several trikes. Trikes suck to try to balance in turns and/or on crowned roads, uneven sidewalks etc. Definitely not something for someone with limited balance - unless everything is paved and perfectly flat where they live.

The concern with a 4-wheeled vehicle is that unless it has some type of suspension to cope with uneven surfaces, or it will only be used in a truly flat place, you run the risk of having one wheel up in the air when the surface isn't smooth. If one rear wheel is in the air, they're not going anywhere by pedaling. Even if the weight is far enough back to keep traction on both drive wheels, for someone with limited balance, that could prove to be an unsafe situation.

Yes, I've put way too much thought into building one of these…

petegossett wrote: FYI Some vintage Schwinn Town & Country trikes have a true differential rear axle - albeit not one with LSD. Also, I built a reverse-trike for a friend who has balance and health issues, and I've bought/sold several trikes. Trikes suck to try to balance in turns and/or on crowned roads, uneven sidewalks etc. Definitely not something for someone with limited balance - unless everything is paved and perfectly flat where they live. The concern with a 4-wheeled vehicle is that unless it has some type of suspension to cope with uneven surfaces, or it will only be used in a truly flat place, you run the risk of having one wheel up in the air when the surface isn't smooth. If one rear wheel is in the air, they're not going anywhere by pedaling. Even if the weight is far enough back to keep traction on both drive wheels, for someone with limited balance, that could prove to be an unsafe situation. Yes, I've put way too much thought into building one of these…

I was hoping that the front fork of the MTB would give me enough suspension. Would it be enough? Would I need anything for the rear?

In reply to tuna55:

I suppose that depends on the terrain, but i imagine it would work ok for pavement. I'd look for some older, but high-quality forks on ebay, preferably ones that both have full adjustment and the ability to swap out springs if needed.

Putting anything on the rear would be more a matter of comfort at that point, but I'd try to avoid it. You won't get much articulation before the chain binds and/or skips off. You could suspend the seat(s) though. Not sure if you're planning one wide bench seat, or using separate bike seats. There are plenty of thick padded & sprung bike seats, as well as sprung seat posts, so that might work too.

tuna55 wrote: I was hoping that the front fork of the MTB would give me enough suspension. Would it be enough? Would I need anything for the rear?

Depends on the forks you get and how much money you want to spend. I would recommend air dampended forks with 80-100mm travel. Plenty of travel, easy to adjust, and light weight. Also, a bit spendy, even used. You likely won't be able to garbage pick them.

Unless you totally luck out, anything you find super cheap or free will have elastonomer or internal spring dampening, neither of which work very well.

Also, def avoid rear suspension for this project. There will be no way to do it effectively without spending a ton of time and even more money. Use suspension seatposts or sprung saddles to get a similar effect.

wpcouch wrote: <bAlso, a bit spendy, even used.

Nothing spendy will make it onto this project. Any cheap ways to make this happen other than just taking and dealing with whatever suspension comes on the front forks of whatever MTBs I find for free in the junk pile?

I do not understand quest well, do you think 4 whelled bike is better than 2? for qhom it is constructed?

tuna55 wrote:

wpcouch wrote: <bAlso, a bit spendy, even used.

Nothing spendy will make it onto this project. Any cheap ways to make this happen other than just taking and dealing with whatever suspension comes on the front forks of whatever MTBs I find for free in the junk pile?

Use Comfort bike forks rather than MTB forks. They will be "tuned" with softer springs/elastanomers to provide a smoother ride, whereas MTB forks will have a stiffer rider since they are intended for more aggressive use

wpcouch wrote:

tuna55 wrote:

wpcouch wrote: <bAlso, a bit spendy, even used.

Nothing spendy will make it onto this project. Any cheap ways to make this happen other than just taking and dealing with whatever suspension comes on the front forks of whatever MTBs I find for free in the junk pile?

Use Comfort bike forks rather than MTB forks. They will be "tuned" with softer springs/elastanomers to provide a smoother ride, whereas MTB forks will have a stiffer rider since they are intended for more aggressive use

The four wheeled contraption is going to weigh a good bit more than a MTB x 2, are you sure the comfy version will be better with the extra weight?

Also, my old-but-midrange MTB has an adjustable fork, but I am unsure how effective it is. Any thoughts?

Fair point. Tough to say, without knowing the final weight of the bike, but you should still be fine. Many comfort forks will have compression adjustments, which would help compensate for the added weight.

Do you know what fork you have on your MTB? Pics?

It's a RST Capa TL, very not great, but it is what it is. I'll likely get something equally bad or worse with my JY hauls.

That should work just fine. Do you know if it's 1" or 1-1/8"? Threaded or threadless? You'll want to be sure to get frames and forks that are compatible with each other.

wpcouch wrote: That should work just fine. Do you know if it's 1" or 1-1/8"? Threaded or threadless? You'll want to be sure to get frames and forks that are compatible with each other.

Whoa there, this is my own MTB, it's not donating parts to the four wheeled contraption. I was just speaking to it's adjust ability and gauging how good a generic adjustable unit would be.

tuna55 wrote:

wpcouch wrote: That should work just fine. Do you know if it's 1" or 1-1/8"? Threaded or threadless? You'll want to be sure to get frames and forks that are compatible with each other.

Whoa there, this is my own MTB, it's not donating parts to the four wheeled contraption. I was just speaking to it's adjust ability and gauging how good a generic adjustable unit would be.

Haha, no worries! Question still applies, though. Make sure (if you don't use the fork that comes with the donor bike/frame) you find an appropriate and compatible fork.

The answer for your steering lies in this pic. Move the handle bars to the driver's side, use a chain and sprocket to connect to the center shaft. This would allow you to get some gear multiplication on your side to help with steering effort.

My favorite part of that bike is the "headlights" that appear to be pointed towards the treetops...

In reply to moparman76_69:

I don't like the chain idea, what I see in that pic is the same bellcank type thing I drew in my pencil sketch like you'd see on an R/C car.

I just found this one on ebay. Not sure you want to spend this much, but hopefully will give you some ideas.

http://www.ebay.com/itm/VINTAGE-SURRY-RED-WHITE-BLUE-2-SEATER-BICYCLE-CAR-1950S-60S-ASBURY-PARK-RIDE-/310803506945?pt=LH_DefaultDomain_0&hash=item485d552701