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Recumbent What IS that thing?! Recumbents may be odd looking, but they have many advantages over a "wedgie" bicycle. Discuss the in's and out's recumbent lifestyle in the recumbent forum.

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Old 02-27-07, 07:14 PM   #1
NuTz4BiKeZ
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Atomblaster or similar

Have any of you guys built the Atomblaster or similar fwd bike?
If so how did it handle?

I built a similar bike and it has a real feeling of pedal steer, is this normal with fwd's?

Thanx for any advice
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Old 02-27-07, 10:33 PM   #2
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Not a fwd trait but a moving bottom bracket trait, it can be lessened by designing the bike with the bb close to the contact patch and the handle bars further away.
Persevere as a lot of people say they find them hard at first, mine is a trike with a mbb/fwd but with alot of the strength of the pedal steer designed out, and lots of ugly built in.
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Old 02-28-07, 08:52 AM   #3
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Ride it a few more miles and you may find that you start to automatically counter-steer by pulling on the handlebars. It's also important to have a nice, smooth pedal stroke - clipless pedals may help in this regard.
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Old 02-28-07, 03:28 PM   #4
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Quote:
Originally Posted by geebee
Not a fwd trait but a moving bottom bracket trait, it can be lessened by designing the bike with the bb close to the contact patch and the handle bars further away.
Persevere as a lot of people say they find them hard at first, mine is a trike with a mbb/fwd but with alot of the strength of the pedal steer designed out, and lots of ugly built in.
Hey

Ugly is the new beauty...

Do you have any pics of the trike as I have been seroiously considering axing the arse end off the bike and making it into a delta trike.

This whole experiment was built around the idea that by utilising the fwd configuration it would be possible to build a modular bike... ie... you could have a bolt on rear for a bike, a trike and even a tandem (by building the rear tandem section with a conventional rwd you woul in effect have independant pedaling and gearing).
It should also be possible to build a delta trike tandem although this isn't something I had really considered tryin, just yet anyhow.
I realise that this would definately not be a set up for the weight weenies but I find that it's great to have access to my tandem and other bikes but it would be better if I didn't have so many bikes to store.

Any how back to the main thing, if you have any pics of your trike I'd love to see them.
Thanx
NuTz
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Old 02-28-07, 11:44 PM   #5
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Here's a couple during the build, it has changed a bit scince. Funny how you like the idea of modular the rear section is bolted in place to allow playing with the design.
the seat is 5" off the ground and I still haven't painted it.



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Old 03-01-07, 12:53 AM   #6
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Thanx for the pics

Hey geebee thanks for posting the pics... It's kinda freaky how alike we seem to think.

While messing around with the front end of my bike I wondered about fitting the old seat tube directly to the fork, this I figured would save some weight.
I also considered shortening the chainstays (I used a rear end from a 26") thus making a tighter and lighter front end all round. The one concern I had was making it too tight for the chain to work without too much angle (sideways).
I also considered shortening the fork as well.... I may still do this simply to tidy things up some.

I have been kicking around an idea of using either forks or chainstays for the rear but used horizontally rather than vertically, I figured it would be tidier and would be a simple matter of a couple of lightish connecting tubes to make the back end.

This would make it easy to attach seat stays and would provide a framework for some kind of built in rear bag or tray.

I am intending to use 406 wheels for the rear so it will be the same sized wheels all round and their smaller size will make it easy to keep the overall size of the trike down a bit.

I havent decided yet whether to use a hard shell type seat or a mesh... Probably try the hard shell first.

The more I think about my original post the more I think I didn't do a very good job of describing the problem, it isn't so much just the pedal steer but more of a feeling that from the motion caused by the pedal stroke there is a quite strong feeling of the bike wanting to turn in that direction, almost like the wheel falling (similar to a bad case of wheel flop caused by far too much trail).
I was wondering if perhaps this is an exageration of pedal steer caused by having weight out front of the front wheel.
The bike has around 3" of trail which I would have thought was closer to being too little rather than too much for this type of bike.

If I get the chance over the next couple of days I will get a couple of pics of the bike so far, it's really only tacked together at the moment so I may still make some changes.
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Old 03-01-07, 10:18 AM   #7
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Quote:
Originally Posted by NuTz4BiKeZ
Have any of you guys built the Atomblaster or similar fwd bike?
If so how did it handle?

I built a similar bike and it has a real feeling of pedal steer, is this normal with fwd's?

Thanx for any advice
I built a bike similar to an atomBLASTER

MBB FWD is great! But be forewarned it's different. Think about it; you're propelling the vehicle and steering all about the same axis! Of course it's going to feel different.

When I was designing the BLASTER, I first put very small handlebars on it with about 4" of tiller. This didn't work well at all, and I was fearful that all was lost with the design. I then put on bars similar to those shown on geebee's trike. These were slightly better, but I found there to be too much knee interference. Finally, I tried Bachetta style bars and the difference was VERY noticable. This style bar allows proper knee clearance (even while turning) and gets your arms far enough away from the steering axis to help counteract the pedal-induced inputs in the feel of the steering.



Another interesting thing I have learned about MBB FWD is that there doesn't seem to be as much of an impact on the self centering effect caused by positive trail. Normally, a very large positive trail value usually means that the steering will feel "slower", when compared to a similar bike with a much smaller positive trail value. This does not seem to be the case with the BLASTER design. Here is a photo of another BLASTER that has a huge positive trail due to the head tube angle and reversed fork, yet the builder indicates the bike handles great.

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Old 03-01-07, 02:52 PM   #8
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Atombikes, I originally setup the trike with a bit more trail but reduced it as the steering was boringly slow, so my experience suggests it has an effect but way less than on some of the other recumbents and choppers I have built.
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Old 08-25-07, 11:08 AM   #9
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my atomblaster type was wobbly at first and my arms were bent some.....then i adjusted the bars so my arms were straight out.............almost locked elbow............that took almost all of the wobble out...........has been a blast ever since and i ride it almost everyday

im already workin on my second bent.....RWD FBB.......i think im hooked

im really glad this section is here cuz i know i wouldnt have bought a bent and i wasnt sure how to go about building one....................til i found BF
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