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rbent Forum
https://rbentonline.org/YaBB.pl General Category >> Technical >> Performance custom seats https://rbentonline.org/YaBB.pl?num=1386937343 Message started by goatstick on Dec 13th, 2013, 6:22am |
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Title: Performance custom seats Post by goatstick on Dec 13th, 2013, 6:22am There has been some discussion regarding carbon seat issues. I had mentioned my RailGun seat a couple of months ago and how the nose is designed to prevent hamstring damage at low seat angles. I have a couple of pictures of a CA2 and an F5 with seats on them now. I should have a better picture of the F5 before long. Both os these seats were specially reinforced for big guys. Both had broken their carbon seats and requested I make a custom seat for them. Both seats are several times stronger than the typical M5-type seat design and are far more aerodynamic and at very little weight cost. I also have some pictures of the new seat for my M5 that fits right down on and bolts directly to the frame. It's been a new experience even for me. The additional rigidity completely changes how the bike climbs. The M5 already is a fast climbing bike but the new seat drastically reduces the effort level (from my perspective) when climbing. It is also very, very aerodynamically efficient, according to my power meter and (everyone trying to hang on my wheel). http://synthetictransport.com/railgun/ I'm not actually trying to drum up business here as I'm backordered and it is a lot of effort to build these things. I'm actually more interested in getting better seat design ideas started. The current crop of options for carbon seats is, imo, fairly poor. We need better. |
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Title: Re: Performance custom seats Post by Rat Rider on Dec 13th, 2013, 6:50am I much prefer the look with the tail box. The detail of the seat on the F5 is hidden by the pad. [smiley=undecided.gif] The later also seems more upright, but that is probably a function of the rider's height. |
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Title: Re: Performance custom seats Post by goatstick on Dec 13th, 2013, 7:09am The F5 rider didn't want a tailbox. The seats themselves are all made on the same mold so the shape is identical. It's the rib that is customized for different mounting arrangements and rider situations. The F5 seat is more upright because the rider's x-seam is so long the seat rides right up against the tire even when fairly upright. Not many options there, though he ordered another seat for his second F5 and I'll be trying out a slightly different rib design on it to allow him to drop the seat back a bit. Having a single rib is far less convenient for mounting on different types of bikes, especially given that most mounts are designed for the std double rib carbon seat. The greatly improved aerodynamics of the single rib seat are the reason I went with it. I don't like posting power/speed numbers on a public forum but I can tell you that nothing else is even close. The seat shape is designed for power. Everyone who rides it and goes back to a std carbon seat says the std seats feel like a wet noodle. They didn't realize how inefficient the std carbon seats were at transferring power to the frame. So... How about some more great ideas for improving the performance levels of our favorite recumbent bikes? |
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Title: Re: Performance custom seats Post by FlyingLaZBoy on Dec 13th, 2013, 11:02am May I assume the F5 version would work on an Xstream? |
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Title: Re: Performance custom seats Post by goatstick on Dec 13th, 2013, 11:59am I have no idea. :^) I expect it has the same mounting system. Is that correct? The RANS front bracket improves the stability of normal carbon seats but is more of a liability for Railgun seats and gets in the way a bit. For the F5 I basically chopped off the rib towards the nose and added a thick mounting pad for that bracket. The shape of the nose requires the use of the forward mounting pins on the plastic clamp to provide clearance for the bracket bolts. |
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Title: Re: Performance custom seats Post by FlyingLaZBoy on Dec 13th, 2013, 6:07pm The current version of the V-clamp only has one mounting bolt. On the oval tube designs, there is no clamp rail - it relies on the oval shape to hold in place. |
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Title: Re: Performance custom seats Post by Rat Rider on Dec 13th, 2013, 10:48pm The single rib appears to match the M5 frame like a puzzle piece. The rib fills in under the seat. Is there anyway to easily shield the open area above the front wheel? http://synthetictransport.com/railgun/rgm5v207_4.jpg http://synthetictransport.com/railgun/rgm5v210_8.jpg |
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Title: Re: Performance custom seats Post by goatstick on Dec 14th, 2013, 10:43am FlyingLaZBoy wrote:
Ok. The F5 had the old V-clamp with the U-bracket. I'd have to see the new stuff to determine how to handle it. |
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Title: Re: Performance custom seats Post by goatstick on Dec 14th, 2013, 10:53am Rat Rider wrote:
I build laminate sheets for the (multiple) ribs and then cut them out to the required shape.There is a strip of 2" wide Velcro between the rib and the frame placed to protect the frame from any incidental rubbing, etc. though it only normally contacts the two mounting areas. It would be nice if the headset could be lowered on the M5 to bring it closer to the tire. Would bring the crankset closer to the tire also, which wouldn't be good though. The open areas could be filled with a splitter. I don't know how that would be handled by the rules for unfaired bikes though. The Apache uses a splitter but again, I don't know what class they allow that bike in. |
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Title: Re: Performance custom seats Post by Bud_Bent on Dec 14th, 2013, 5:20pm Beautiful seat! |
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Title: Re: Performance custom seats Post by goatstick on Dec 14th, 2013, 6:02pm Bud_Bent wrote:
Thank you. I will say that it really has been a community effort. There have been a number of people who conspired with me to push the boundaries of how to deal with low seatback angles and even that wouldn't have happened without the general support and encouragement of just a lot of people pushing me to ride and race. A number of those people are rbent members and I thank you. I'm not making these seats to sell them. I really started doing it just to fix my problems. the first few seats were design experiments and pretty rough, but served their instructional purpose. I'm currently only making them for people with various problems that can't (or can't easily) be solved with what else is out there. 30-some odd years of r&d has shown me that it is very important to discover the boundary conditions early on, and the seats I'm making for big and/or hefty riders that overwhelm standard carbon seats are certainly boundary conditions that so far I've dealt with, and their riders have been delighted because the seats not only survive them but they get to go noticably faster also! I really get a kick out it. I'll be making seats for normal people soon. I have a few special people waiting in line for one and hope they don't have to wait too long. It takes an amazing amount of time, expense and effort to fabricate these things. However, this community should feel proud to have helped these guys out, and I sure hope more will come of it. Five years ago it would never have crossed my mind to build c.f. bike parts and now I'm doing it! Don't let life stop you from doing things that you should be doing and having fun doing! Just figure out a way to do it and when you need it, ask for help from your friends. I think they'll love being a part of what can happen. Thanks Again! |
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Title: Re: Performance custom seats Post by Rat Rider on Dec 15th, 2013, 7:27pm The F5 rider likely is a big dude. Looks like he saved his team photo from his playing days on the '83 NJ Generals football team. [smiley=thumbsup.gif] |
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Title: Re: Performance custom seats Post by Rat Rider on Dec 18th, 2013, 10:43pm The new pic of the F5 is only marginally better than the first. Is that guy riding an XL frame? He is so far over the back wheel, it must be be a pretty squirrelly steering beast. The seat on the M5 reminds me of why I have gravitated to each iteration; the shoulder area is very wide. I gotta think it is one comfortable seat. |
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Title: Re: Performance custom seats Post by goatstick on Dec 19th, 2013, 7:32am Have to wait until he has something better than a camera phone. Yes, an XL. It is very comfortable unless you just ride around for a long time on it without your lower back in tension and your glutes barely touching the seatpan, as it is designed to be ridden. The F5 rider has ordered another seat for his other F5 and I'll slightly modify the design, now that I know more precisely what he needs. I hope to be able to take a picture of that myself. The important lesson I learned from making these seats is that what feels good when you just plop down and pedal gently is quite a bit different from what feels good when you are generating power. The old belief that making a mold of your back when laying down on the seat really just doesn't work. I tried it and that provided the worst seat of all of them. I had to gradually modify that until the pressure points were in the right place so they provided support where you need it. Not where it feels good when relaxed. That's why I warn people that this is not a seat for relaxed riding. You can make it much better by putting more padding under the pelvic area so it doesn't put too much pressure there, but that's not what it is designed for. I actually do slip a little more pad under there when I'm doing a long leisurely-paced ride with friends. |
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Title: Re: Performance custom seats Post by Denman on Dec 21st, 2013, 5:14pm Those aren't seats, they're beds. |
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Title: Re: Performance custom seats Post by Mizta_Nice on Dec 23rd, 2013, 6:44am Denman wrote:
Yes they are, but I bet they're comfy, comfy beds. I've finally gotten to the point where I'm almost too laid back, but I loves it. |
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Title: Re: Performance custom seats Post by goatstick on Dec 23rd, 2013, 9:37am Yes, they are very comfortable to 'sit' on as they support the body very well. J. Tanner and I have had many discussions about how a recumbent seat should be. He's a LMT and works for a group of doctors in that capacity so has a huge amount of technical information on how the body should be supported. He's the only rider I know of who uses a lower seatback angle than I. About three or four years ago we realized we were trying to accomplish the same things but were using different means which were both very successful and we began discussing how a recumbent seat should really be shaped and have continued over the years. Every time I have him try the latest seat out he gives me excellent feedback on why what I have done works so well from a physiological standpoint. One of these days I likely ought to discuss that background. What we've found is pretty much the opposite of traditional recumbent seat design so far and when you take a close look, it's pretty obvious why. Tanner has gently tried to explain the principles to a certain recumbent company to no effect. Not that anyone is asking them to actually make any changes but maybe just to slow down the disinformation so people have the knowledge to make the right choice they need (whatever it is). |
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Title: Re: Performance custom seats Post by FlyingLaZBoy on Dec 24th, 2013, 9:30am So, under a "power" situation on a seat less than 25 degrees (or REALLY reclined like you ride), where is the ideal support coming from mainly -- the lower back / pelvic area, the middle of the back, or shoulder blade area? The XL Hoagie seat is comfortable, with good stiffness (relatively), but after the first few times of riding it, the siderails were pressing too much into my lower back -- so I added some foam to reduce the curvature down there. Now, under power, it seems that I'm supporting it in the mid-back and shoulderblade area. |
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Title: Re: Performance custom seats Post by goatstick on Dec 24th, 2013, 10:53am Covering a few bases very briefly (need more time to cover adequately). Several issues come into play, depending on what sort of riding you do. For short, fairly infrequent rides, you might not encounter issues and that seems to be the case for the large majority of recumbent riders. It's when you start riding more frequently and for longer periods of time that issues tend to develop. Those issues tend to be related to the sacrum and coccyx first and then may spread to spinal issues if the rider doesn't already have those. Pressure on the coccyx (tailbone) can be very painful and can cause nerve damage fairly quickly. You may have noticed that most of us ultra riders use a lumbar support panel of some sort on conventional carbon seats. This is to allow the lower back to carry the weight and clear the tailbone from stress. While there are many ways to accomplish this, a higher seatback tends to concentrate pressure over a smaller area. As the seatback is lowered, that weight can be distributed over a much larger surface area, spreading further up your back. If you take a look at diagrams, etc. of the sacrum, you might see the network of blood vessels and nerves that penetrate it to connect with your legs. Pressure on the sacrum can restrict blood flow to your legs and again, pinch and tend to inflame nerves that control and respond to leg muscles. Since the blood vessels transport fuel to the leg muscles it is critical they not be constricted. I can tell you that pinched or otherwise constricted nerves in that region can cause long-lasting problems that most certainly restrict power generation. So what positions allow you to make power and especially maintain it? People point to some writeups done a few years back claiming that the closed, more upright position allowed for greater power generation. I have no idea how those experiments were performed. As a research scientist for many years, I am fully aware of how important it is to properly set up and perform experiments and how badly the results can go astray when this is not done. I also know that experimental results can be taken out of context and accomplish the same thing. I'm not sure what the case here is but I do firmly believe and have shown with my own results (and others who have used my methods) that the closed position simply does not guarantee more power or better/faster climbing. Nor does the open, low seatback angle. Success depends on getting things right! And that means you will need to spend some time investigating what is right for you and how to prevent possible coccyx and sacrum issues from inhibiting comfort and power production. Existing recumbent designs tend to not provide the sort of protection for the coccyx and sacrum that many (if not most) people need. You will need to find something that works. I will say that a few seats I've seen recently are starting to get closer and hopefully are beginning to recognize these issues. Outside of comfort and power production there is simple wind resistance. If you can generate the same power in either the closed or open positions, which do you think will be faster? :^) As to your question of support and the mods you have made, it sounds like you are on the right track. If you can arrange to support your pelvis so that it is easy to use it as a lever to slightly lessen the weight your glutes put on the seat, this will also improve bloodflow to the legs... Distribute the pressure out across the top to the sides of your pelvis so it is not concentrated, then you can lock your pelvis into the seat and generate your power from there. No need to bridge and bring the upper back muscles into play. Let them do their job of just supporting the frame. This relieves pressure from the shoulder blades, etc. also. When you get it right, you can use that little pelvic tilt to greatly extend your power generation over time. You might need to build up a few muscles to do it, but I think you will enjoy the results. |
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Title: Re: Performance custom seats Post by goatstick on Dec 25th, 2013, 3:21pm Woah! Been a while since I've ridden a stickbike with a stock carbon seat. I spent a bit of the day overhauling my daughter's Corsa 650 (my first stickbike) and my wife's CA2 650 (my second stickbike). I'll normally spin around the block to check things out after working on them but took both out for a little longer spin afterwards and I have to say "How the @#$@#! do you people ride these things?!??" Seriously! :^) I rode the CA2 700 with my prototype seats for a year and then moved to the M5 with my first RailGun seat and both B seats are so unbelievably rickety and uncomfortable! I can't believe I was crazy enough to be doing 60+mph downhill in the middle of the pitch-black night during RAAM 2010 on that very same CA2 650! I've been putting off making RailGun seats for both bikes because I thought other people needed one more but both are up for replacement as soon as I thin the orders down. I see I need to be far more patient when riding with my friends on the stock seats than I have been... |
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Title: Re: Performance custom seats Post by FlyingLaZBoy on Dec 26th, 2013, 9:24am I've also noticed that the other thing that happens with recumbent seats is the effect of compression of the foam... the "filter foam" of the Hoagie is typically compressed to one level under normal riding, but when you start pushing, it compresses further, which slightly changes your effective seat-to-pedal distance and leg extension... so you have to set your seat such that you're not overextended under power. Would you say this is partially fixed by going to a denser pad? Which then transmits more vibration, of course -- everything's a tradeoff... |
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Title: Re: Performance custom seats Post by goatstick on Dec 26th, 2013, 2:55pm It's best resolved by moving to a low seat angle. :^) When you are lying down and the foam compresses, it compresses mostly down and not back. As to foam type, I have never found any special type that works that well for me. I just improvise according to the conditions. On a rough road, it is nice to have a thin layer of more dense foam under the filter foam to help absorb some of the impact. People seem to really differ as to foam type preference. |
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Title: Re: Performance custom seats Post by goatstick on Feb 3rd, 2014, 9:05pm Rat Rider wrote:
I built another RailGun seat for this guy for his other F5 Pro. He wanted to have a seat that could recline all of the way back on this bike so I had to build another custom rib. It is likely close to 10x stronger than the one I built for my M5 but is a little heavier also. I replaced the old F5 pic with the new seat and other F5. The pic shows the seat stays on the second to last hole but he ended up having to move the seat a half-inch further forward than he thought so he can move to the last hole and likely still clear the seatback. He is really laid back for such a big guy and yes, that's a fair amount of weight aft of the rear axle. Neat thing is the bulk of his weight has actually moved forward; about 2 1/2". Give him a little bit of time to get used to the position and I expect he'll be much more stable on it than before. I also worked out a better (and far stronger) way of supporting the front seat mount on this seat. And yes, he loves the seatback flair. I still laugh at that as it never crossed my mind that the flair would be such an attraction. I did it to be able to bond the tailbox to the seat more efficiently and strongly. Every rider who has tried it out loves that feature. |
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Title: Re: Performance custom seats Post by goatstick on Mar 13th, 2014, 1:36pm There have been a number of questions being asked about the RailGun seat in different venues so I decided to make a FAQ: http://synthetictransport.com/railgun/faq.html Let me know if you have any more questions. Greg!! Contact me before you start mounting the seat! I have a few instructions for you. Also I need to tell you how to work the lid latch. Have to be fairly gentle with it. |
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Title: Re: Performance custom seats Post by aikigreg on Mar 13th, 2014, 8:58pm Will do. It may be a while. |
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