Recumbent - Just finished my homebuilt bent
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I just finisned my homebuilt to the point where I could test drive it.
All went fair. The seat kinda sucks, but that's because it's part of a fiberglass chair seat, which I made do until I see what the story is.
The one thing, that I noticed the most, was the steering super sensitivity. I don't know whether it's my inexperience on bents or some flaw in my engineering.
The steerer is in the center of the frame, with a link connecting to the front steering spindle.
What is your guess? Do bents seem to be very sensitive, when first climbing aboard?
I guess, I should add: It's a LWB, ... about 7-1/2 feet.
Does anybody have a source for seats?
I'll get some pix in the near future.
At this point, I'm in no position to comment on the engineering of your bike. I've ridden recumbents twice, one LWB and one SWB. Both seemed "strange" but I don't know if I'd call it super sensitive. Is your design like this? (Marauder)
As far as seats, what are you looking for? Here is something you might find useful: http://www.geocities.com/atombikes/seat.html
Inexpensive and gets the job done. There are plenty of more expensive ones that look GREAT!
If you feel like making your own seat, here are a few sites that you might find useful...
Hope That Helps
How about the Sun EZ seats? They are available on eBay.
They aren't exactly what I had in mind, however they might be great and get me over this stumbling block..
05-14-06, 08:06 PM
Great news fellow-homebuilder! I almost used a fiberglas shell or metal framed chair bottom. Check out my seat. The back pad is now only 3/4" thick though, not the white shown. Frame bought from Denny LaDue and I installed all components myself from discarded bikes. All parts like new. It's a pleasure to ride.
Yes it seemed sensitive steering-wise at the beginning. I found that I have to consciously make myself relax my arms and "hang" them on the bars. If done will smooth out the steering I find. But from all our lives on DF bikes, our upper bodies are used to being tense. It's time-consuming to retrain our whole body to a completely different geometry of riding. But I love it. I'll probably never ride my DF bikes again. And mine's about 8' long, 6'6"/230lbs. here.
05-14-06, 08:51 PM
With indirect steering, you can alter the steering ratio by changing the length of the arms that the steerer rod connect to. If the arms at the headset and the stem are the same length, that's 1:1 steering. Making the arm at the headset longer will 'gear down' the steering and make the bike less sensitive.
that's 1:1 steering. Making the arm at the headset longer will 'gear down' the steering and make the bike less sensitive.
Ah-hah! Basic gearing formula/realationship. Well, mine would be 1:1 at this point.
Would it be of an advantage to 'gear it down'? Or will it be better at 1:1, after I get the hang of things?
05-15-06, 09:24 AM
If it were me, I'd ride the bike as-is for a while, then make that determination once you're acclimated to the recumbent position. Like World Tour sez, you have to ride with your upper body relaxed - and relaxing is no mean feat when you're doing something new and your skin is at stake! Assuming your geometry is anywhere near what would be considered 'normal' then you'll probably get steadier within a few hours' riding.
Here are few pix. Of course, the seat will get burned as soon as I come up with an alternate. And after all mod.s are done, a little paint might get applied.
I've shown the front steering configuration. Also, I've shown both sides of the "free front" with chain rings and derailleur. I used this free front, because initially, I was thinking of additional upper body propulsion. I kind of scrapped that idea because of the interference with steering. However, I see the possibility of adding a motor drive to either side.
For those not familiar with the "free front", it's a ratcheting affair, in so much, as the center spindle (crank) can "coast" or drive in relationship to the chain rings.
Thanks to you, who have offered advice, links and pix.
I've got to get the seat taken care of and then, I think, I'll move on to an engine. I'll see how it goes, first. Here in North Eastern Pennsylvania, it's not exactly flat! Plus, I'll need a new project.
In my last post, I mentioned that I needed a seat, which would offer a little comfort.
I was scrounging around on the Internet to see what I might find, before I broke down and built a seat and came across the Recumbent Bike Riders (http://rbr.info/) site. Rob, the owner, gave me a call after I emailed him and it turns out he had a used Bacchetta Re-curve, which he was willing to let go. That should be here tomorrow and hopefully that will do the trick.
The other thing that I wanted to mention, in looking over his site, I noted that he is having a bike and trike rally this weekend. The rally is from May 19th-21st 2006 at State College, PA. It sounds like fun, so maybe I'll do an official "Recumbent Tour". (I don't mean "ride!" Maybe, someday.)
Ok, here's the latest picture with the Bacchetta seat installed. I guess, I'll have to weld a couple new tabs on the seat stays, as the struts are stretched to the max.
I think, I've got to do something with my gearing. Of course, I haven't ridden in years, I've never been on a bent before, and I'm way out of shape. It seems like I'm going to need more bottom end. I've got a mix of chainrings, cogs and cranks. Having the middle chainrings seems to confuse things, I guess. I can't really change the middle ones, due to the fact that they are part of a "free front". The front crank chainring and or crank length can be changed.
Anybody have any thoughts on how to approach this? I would guess, I should do the gear/inch thing for a start. What is a good number for the low end of a bent? Keeping in mind, that I'm in the hills of Pennsylvania.
I was looking around last night and came to the Longbikes (http://www.tandembike.com/) page.
Two things that I found of interest to me were first, the Slipstream (http://www.longbikes.com/Slipstream.html), which looks very much like my build. The second thing was their Eliminator (http://www.longbikes.com/Eliminator.html), which has a drive configuration similar to mine.
Looking at their ratios, it looks as if I should drop the crank ring from 52T to about 30T. Am I reading this correctly? My chain rings are 52T and ??T for the smaller one.
05-21-06, 08:30 PM
What size rings are you using? The formula for gearing will be:
(front chain front ring /front chain rear ring) * (rear chain chainring/cassette teeth)*wheel diameter
As you can see by the formula, if the front chain has the same size ring at both ends, the result for that portion of the formula will be 1. Most bents try to aim for a gear range of 25-100 inches. Unless you find a way to put 4 chainrings on the middrive or shift the front chainrings too, you will be limited to two functional chainrings.
Originally I was using front chain: 52/52, as the original chainring/der was 52/39 and as you point out, it would be 1 from crank ring to chainring. But, as it turned out, I had no bottom end. The cassette is 11/13/15/18/21/24/28. On the center cluster, it's a 52T drive ring (from front crank) and 52T/39T chainring to the cassette.
I put a different crank on with rings of 24/39/?? (I'm not positive of those numbers. I looked at more than one). The 24 was too low. The 39 seemed about right. The big ring, I didn't try. (reminds me of Goldilocks and The Three Bears.) It looks like it comes out to around 27 - 92. I had my son-in-law ride it, as he's more current. He thought, it seemed pretty good. So, I'll try it out for a bit
Why not just put lower chainrings on the front? Check this out:
With this can make a Quad or Quintuple chainring for the front, with as low as a 16 tooth chainring.
That looks like a very useful option.
However, my mid drive/chainring assembly kind of has to stay, due to the fact that it's a "free front". They are anything but standard. I could get rid of the "free front", but was kind of saving it, as a means to add an "alternative propulsion", which is in the back of my mind.
I was just thinking, if my set up doesn't work out, the Mountain Tamer setup might be an option. As a matter of fact, looking at it more closely, the "free front" uses a similar spline on their rings. What are the chances of it being identical?
Not sure, but ask the guys at Mountain tamer they are very knowledgable.
06-12-06, 05:44 AM
I like your setup. I'm currently working on my own homebuilt bike. Mine is a quad. I'm using a single ring up front and a 7sp cassette for my intermediate drive and 6sps in the back. I haven't had a chance yet to sit down and calculate the gear inch. If needed I'll put a 2 or 3 ring setup on the front but currently I'm just trying to work out the steering.
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