badmother

I made this one, https://www.flickr.com/photos/23770381@N03/2263917806/ , my first one, and now I want to make another one. Reason is I realised that forcing (cold) the chainstays together on this alu bike is not making it safe to ride, so to get a bike I can rely on for longer trips I want to make another one.

I always ride with my Bordercollie. This is why I like this bike, I can give him a lift when needed.

For that reason, and since I am getting older and more cranky, I would like to use a steel womans MTB bike I`we got (not so bad quality), to make it easyer to mount and for all the ekstra "hasseling around" with the dog and so on.

These bikes has got a weaknes in that the seat tube tends to bend just a little where the top tube is atatched to it. Culd this type of bike take the ekstra strain from being converted into a longtail, or should I go for a "sloaping toptube" male MTB? Hope you can tell me.

rustguard

i've never seen a mid or top end step through, sloping frame is the strongest, step through only good if you keep the weight over the back wheel or if it weighs a ton, If you are investing the time, effort and money to build why start with an inferior frame. If you can find one a few manifacturers make curved top tube frames for just this reason, so you have the best of both worlds. I cant remember offhand who makes them but I know KHS does.

rodar y rodar

That`s a nice job, Badmom! Did you bend all that tubing yourself? As to your next bike, it seems to me that you could be right about the extra stress. A "women"`s frame has a pretty low triangle and with a super long wheelbase it might get to be like pedaling a trampoline. Have you thought about starting with a mixte frame? Or maybe an old tandem? Some of them had a very low step-over and were supposedly designed to deal with long frame issues.

badmother

Did not bend, found something in the "bikecontainer" that could be used, but bending tubes is something I want to learn..

I did think of a mixte, I like them alot. Only thing is the ones I find around here is often small, often heavy, often the old fashioned crank system and almost always 28" wheels, I like 26" for longbikes. I know I could just use 26" in the 28" fork, change the fork, BB adapter and so on, but just now I am impatient, so taking time looking for parts is not what I want to do just now..

rodar y rodar

Is the "extra" on your extracycle removeable? Maybe you could try it on the bike you have on hand and keep your eyes open for something more suitable. I don`t know about the availablitiy in your area, but mixtes were made in just about every wheel size imagineable. You might run into something else too- maybe just a women`s frame built like a tank. And I still think tandem frame would make a great extra, but I`ve never gone "extra", so might well be overlooking something.

badmother

Removable but some work involved, no welding. I am thinking the same as you. Also I find that every time I build something it gets a little bit better, so maybe the third "longbike" is going to be the perfect one. I`we got friends who needs longbikes but would not try to make one, so I could get rid of the "less perfect ones" that way. Looks like at the moment I have this urge to make longbikes. Got fed up with knitting you see..

NoReg

If you fixed the headtube of your bike in a giant immobilizing vise, and pushed up on the rear wheel, a longer wheel base would generate proportionally greater leverage. However in the case of an extracycle, when the rear wheel pushes up, the rear axle goes up less high, which should be a gentler shock to the frame. Nothing in the original frame is fixed to allow this leverage to do anything nasty to the forward triangle.

What is quite different in an extracycle is that the load in the rear drops is not isolated there. The drops are a pivot point around which the rear extra frame pivots, except that struts restrain it. This could create weird loads ahead of the rear triangle, if these forward forces are not braced by a well placed strut. I can't see your full photo, but it appears to brace these loads to the bottom bracket, in which case they should not travel forward to the front "triangle".

As long as your weight is not excessive for normal use in the frame style chosen, and as long as you do not use a bike so converted to do harsh stuff the original frame couldn't have withstood, you should be OK.

However, I don't even play an engineer on TV.

badmother

Problem solved for now. Found a mixte like offroad bike today, good quality, paint not looking good but not important. the top tube is not split in two as on a real mixte, byt the two extra stays from seat tube to the rear wheel mount is there. Struggeled a long time to get it out of the container, it was stuck!

The system I use is much the same as for the xtra, so I think te strain on the frame is the same.