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Frankenframes

We are starting to see more and more polo specific frames designed by a number of companies, but I am curious about all the modified non-polo specific frames that are out there. Did you shorten the rear triangle, welded in some tabs for disc brakes or made your own coupling system for easy transport, post them here to inspire others.

I´ve modified some 90s MTB frames for me and my buddies.
What I love to do:

Shorten the rear end as much as possible.
Lift the rear and in that way modify the headtube angle to about 74 degrees as well as lift the bottom bracket to about 290-300mm.
Straighten the forks aiming 68-80mm trails.
Chopped rear end and straightened fork mostly end up in a wheelbase of about 96-97cm.

Some examples:
http://www.miwis-bastelbu.de/Galerien/bikepolo/slides/bikepolo33.jpg

http://www.miwis-bastelbu.de/Galerien/bikepolo/slides/bikepolo36.jpg

http://www.miwis-bastelbu.de/Galerien/bikepolo/slides/bikepolo47.jpg

http://4.bp.blogspot.com/-HAGu3lToSu8/T-yqsPMkCRI/AAAAAAAAAEk/9waWFi8vE7...

Cheers, Michael

  • IMG_0913.jpg

respect.

Combination of choice: Smash + Bang

Great work! Did you have any trouble bending the rear triangle and forks? Didn't it create any weakness in the steel? Did you use any kind of jig to keep the frame aligned? (Sorry for all the questions)

I'm thinking of doing something similare, at least shorting the back and straighten the fork. Also raising the bb might help with my headtube angle, which is about 80 degrees now.

Hi Erik.
I made myself some POM chucks for the forks. Bended the forkblades cold (important) and measured often to reach the desired offset without having to bend back. If you only bend ones and you do it with good support / chucks, it will last very very long. I rode some of those frame myself for long time. I am 191cm and about 100kg/220pound and a real aggressive driver. Never had any issues.

I measured the first mordified forks on an even surface (cheap old stonetable). Step by step a made myself some measuring tools and some diy fixtures to make alignment easier.
I now use my homebrew fork jig to check the alignment, but you don´t necessarily need those stuff.
http://www.miwis-bastelbu.de/Galerien/Fleur/slides/FDL98.jpg

Quite the same procedure for the frames.
First I measured on an old stone table + 3 supporting blocks.
Like this:
http://www.miwis-bastelbu.de/Galerien/Fleur/slides/FDL124.jpg
For the rear triangle some filaments and a well centered wheel is enough.
Like this:
http://www.miwis-bastelbu.de/Galerien/Fleur/slides/FDL142.jpg

Some weeks ago I made myself a frame jig and now I can put thos Frankenframes in that jig to modify the rear. It works great and is real fun, but you don´t need that kind of stuff to keep a modified frame aligned.
(The main reason for building that frame-jig was, because after some Frankenframes I just wanted to built my own polo-bike from scratch)
http://www.miwis-bastelbu.de/Galerien/Pitpony/slides/pitpony008.jpg

  • pitpony008.jpg

So sick! Start your own thread and give sweet updates of all the cool polo bike stuff you do. Is that frame in last picture of your own creation?

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fixcraft.net

MiWi wrote:

Hi Erik.
I made myself some POM chucks for the forks. Bended the forkblades cold (important) and measured often to reach the desired offset without having to bend back. If you only bend ones and you do it with good support / chucks, it will last very very long. I rode some of those frame myself for long time. I am 191cm and about 100kg/220pound and a real aggressive driver. Never had any issues.

Do you have any pictures of that setup? Want to try to bend my fork straight first, but have a little trouble creating a strong enough fixture to clamp them in. Also, it seems hard to clamp the fork in without damaging it.

Erik wrote:
MiWi wrote:

Hi Erik.
I made myself some POM chucks for the forks. Bended the forkblades cold (important) and measured often to reach the desired offset without having to bend back. If you only bend ones and you do it with good support / chucks, it will last very very long. I rode some of those frame myself for long time. I am 191cm and about 100kg/220pound and a real aggressive driver. Never had any issues.

Do you have any pictures of that setup? Want to try to bend my fork straight first, but have a little trouble creating a strong enough fixture to clamp them in. Also, it seems hard to clamp the fork in without damaging it.

I missed that part, sorry.
No I don´t have pictures of that. But it´s a really simple setup.
I made three Delrin/POM jaws and put those jaws and the fork in a clunky old vise.
I need another guy to hold the fork in place while I close the vise.

Similar to this wooden jaw.
http://alexandchristine.smugmug.com/Bicycles/Framebuilding/Ivy-T/P108011...

On the one side I place the first jaw near the canti bosses, the second near the dropout. As the vise is not wide enough to span that distance, I put a solid iron-bar on that side behind the two jaws.
The third jaws is then placed on the other side quite in the middle, where the archrise is the biggest.

In that way the fork doesn´t get any dimples and in most cases even the paint does not get hurt (sometimes micro-cracks in the paint occur).

Ah, so you don't actually bend it by hand, but by closing the vise. I'll give it a try, hope my vise doesn't break

I guess it is nearly impossible to straighten a beefy fork by hand and I think it would be rather incontrolled.
With a vise (or a hydraulic press) you can controll the bending much better and do it in really small steps to reach the desired value and match both forkblades.
(I don´t know how rigid a vise has to be to bend a fork. Mine is quite old and heavy, I guess at least 60kg. But smaller ones should do it as well.)

If you don´t have a strong vise, maybe making a rigid frame and using a (strong) car jack is an option.
Something similar to that:

  • Cider press2543563.jpg

I used the vise and, a piece of flat steel and three chucks out of UHMWPE, worked like a charm. First the fork tended to slip out of the chucks, but a few pieces of innertube solved that.

The only thing I find hard is determining the amount of rake while your bending. Just have to do it in small steps i suppose, but it would be better to have a jig with measurements in which you could bend the fork.

Next is making a jig to fix my frame in so i can put in new drop outs. That way it is totaly fixed for the welder to do his job.

Nice to hear it worked out with your fork.

I have to do it in small steps as well.
Some king of adjustable stop would be a nice thing to match both blades. similar to what the fork-blade benders have.

For the rear dropouts:
Something similar to this would work out good for frame-modifications.

I will have to fix both the front fork axle and bb in place to be able to determine the right position of the rear axle. There might be a better solution, but not with my limited resources onfortunately.

By the way:
Are you sure your headtube angle is really 80 degrees ?
Most bikes have 72 - 75 degrees. 75 degrees are mostly track or trickbikes and that is quite steep, if you look at those bikes. The pink bike shown above has 74.5 degrees.

MiWi wrote:

By the way:
Are you sure your headtube angle is really 80 degrees ?
Most bikes have 72 - 75 degrees. 75 degrees are mostly track or trickbikes and that is quite steep, if you look at those bikes. The pink bike shown above has 74.5 degrees.

It's a guestimation, based on side a side view foto measurement. I'll of course measure it properly before I start cutting anything.

"So sick! Start your own thread and give sweet updates of all the cool polo bike stuff you do. Is that frame in last picture of your own creation?"

Thanks.
Yes, the picture with the jig shows the tubes of my own frame.
I wanted to teach myself TIG welding and did a frame http://www.miwis-bastelbu.de/Galerien/Pitpony/slides/pitpony015.jpg
and a fork http://www.miwis-bastelbu.de/Galerien/Pitpony/slides/pitpony016.jpg

I ride it for a few weeks now and love it.

  • pitpony028.jpg
MiWi wrote:

"So sick! Start your own thread and give sweet updates of all the cool polo bike stuff you do. Is that frame in last picture of your own creation?"

Thanks.
Yes, the picture with the jig shows the tubes of my own frame.
I wanted to teach myself TIG welding and did a frame http://www.miwis-bastelbu.de/Galerien/Pitpony/slides/pitpony015.jpg
and a fork http://www.miwis-bastelbu.de/Galerien/Pitpony/slides/pitpony016.jpg

I ride it for a few weeks now and love it.

Did you take any classes to learn TIG welding or just trial and error?

When are you starting production with the bikes? :P

I didn´t take any classes.
I tried to read as much as possible about it.Then I just tried it on my own. First practice-welds were quite ugly, but I got better quickly ( few hours or so).
The first welds on the frame are not that nice (headtube, seattube). But it got better with the bottom bracket and the rear end. In the end the welding of the fork went really nice.
Not as a pro would have done, but I don´t doubt that they will last. (As far as I can judge as a civil engineer and welding engineer.)

Knowing how things work theoretically can´t substitute spending time on the workbench and practice. But it was a good starting point to know how it should be done and what influence different things will have, what mistakes typically occur and so on.

There will be no production of bikes. I´m just some kind of a gearhead and always busy with something. I´m just fooling around, doing some DIY stuff for me and my buddies.

What is your source for tubing and other frame parts (dropouts etc)?

Since I'm not able to weld myself Im thinking of cutting and modifying the frame myself and secure it in a jig, then have it welded by someone else.

I buy all my stuff from peter at ceeway.
www.framebuilding.com
He is very friendly and helpful, got a huge range of stuff and always has very good pricing.