Planning Ahead
- Thread starter MrSteve
- Start date
JonB
Zen MBB Master
New idea for suspension.
Based on a thread in alt.rec.bicycles.recumbent called cost to build bikes and my previous idea about a U for seat suspension i came to think more of the idea of using leaf springs as suspension.
The idea is to use less materials for manufacturing and much less time for assembling the bike, making the bike cheaper. The current spring coil needs the screw in the middle, and you have to assemble the parts into a suspension. A leaf coil is just a piece of alu/steel profile bent and twisted into shape.
1) using a leaf spring for total seat suspension. Imagien a long alu profile or steel profile which is mounted at the top of the / part of the frame, that usually goes from the bottom bracket to the handle bars. At the moment the freerider/sofrider has a ---- going out in the middle that holds the seat. But a long alu/steel profile bent the right places might provide suficient suspension, and you dont need to weld the ---- to the /, just screw the alu/steel profile to the / and attach the seat to the profile. In the back of the seat you dont need the current tube to hold the seat, because the profile runs all the way from the handlebars down under the seat and up to the top of the seat.
2) using a leaf spring to provide suspension to the back wheel. Again attach a alu/steel profile to the / but this time under the seat and then split it up so it goes out both sides of the wheel. This would also make replacing the rear end with other options really fast. unscrew some bolts and let the profile slide out of the slot made just for that. The profile should still be attached to the rear wheel.
3)Or you could bend it upwards from where the bottom bracket usually is and just let the existing rear wheel holder frame press against the profile.
4) the front wheel can somewhat be mounted in the same way if it is pushed a little forward from the head tube.
Based on a thread in alt.rec.bicycles.recumbent called cost to build bikes and my previous idea about a U for seat suspension i came to think more of the idea of using leaf springs as suspension.
The idea is to use less materials for manufacturing and much less time for assembling the bike, making the bike cheaper. The current spring coil needs the screw in the middle, and you have to assemble the parts into a suspension. A leaf coil is just a piece of alu/steel profile bent and twisted into shape.
1) using a leaf spring for total seat suspension. Imagien a long alu profile or steel profile which is mounted at the top of the / part of the frame, that usually goes from the bottom bracket to the handle bars. At the moment the freerider/sofrider has a ---- going out in the middle that holds the seat. But a long alu/steel profile bent the right places might provide suficient suspension, and you dont need to weld the ---- to the /, just screw the alu/steel profile to the / and attach the seat to the profile. In the back of the seat you dont need the current tube to hold the seat, because the profile runs all the way from the handlebars down under the seat and up to the top of the seat.
2) using a leaf spring to provide suspension to the back wheel. Again attach a alu/steel profile to the / but this time under the seat and then split it up so it goes out both sides of the wheel. This would also make replacing the rear end with other options really fast. unscrew some bolts and let the profile slide out of the slot made just for that. The profile should still be attached to the rear wheel.
3)Or you could bend it upwards from where the bottom bracket usually is and just let the existing rear wheel holder frame press against the profile.
4) the front wheel can somewhat be mounted in the same way if it is pushed a little forward from the head tube.
I can't argue with some holes in the seat.. add some ventilation and reduce weight without giving up any significant amount of strength. And I definitely agree with not changing the ergonomics of the overall layout and seat height. All that is a big win exactly as is.
I doubt there are any huge weight savings to be had with lightening the existing suspension though, marginal improvement like John said.
It's the lighter frame design enabled by a rear triangle that I believe could give a more than marginal weight loss. I think the road bike philosophy is that suspension comes from selecting appropriate tires for the roads you'll be on.
- Mark
I doubt there are any huge weight savings to be had with lightening the existing suspension though, marginal improvement like John said.
It's the lighter frame design enabled by a rear triangle that I believe could give a more than marginal weight loss. I think the road bike philosophy is that suspension comes from selecting appropriate tires for the roads you'll be on.
- Mark
Mark B
Zen MBB Master
To a certain degree, I have to go along with what you say about tire selection. Unfortunately, here in SoCal, we have a mixture of smooth, new roads and roads torn up bad enough to resemble cobblestones. :roll:
Road bikes have gone a lot to carbon fiber seat and chain stays to reduce road vibration. Carbon Fiber has it's weaknesses, but it is very effective at lightening a bike and making the ride much smoother. The one thing I notice about the Silvio is a good amount of road buzz going right up through the seat and into the back. It doesn't bother me, but I do notice it. Especially since I have been running higher tire pressure in the rear to compensate for reduced tire pressure in the front. So definitely, I think there needs to be some kind of dampening system in the back. Perhaps a combination of carbon and elastomer. Maybe a good start would be to redo the seat stay/wishbone thingy on the current model of Silvio to a carbon unit. Yes, the weight savings would be minimal, but it could potentially improve the ride a whole bunch in combination with the elastomer already in place.
As far as the main body part of the Silvio; maybe you could eliminate the dead space under the seat pan and save a few grams. But otherwise, the ergonomics are almost perfect as they are.
Moving forward; all the adjustment clamps add weight to the bike. I realize you need them, but perhaps carbon, or ti could be used in their place. I don't like all the redundant dropouts. That's a lot of cast and machined parts there and surely a better way could be arrived at to shave off some grams. What about a carbon fork? What about making the entire front end carbon? Leave the main frame pretty much as is and go carbon fore and aft? You could market that as a retro-fit kit, too.
In short, I don't think you can point to any one area of the Silvio and say "here's where we can lighten it up". It's not one big thing that adds weight, but a lot of little things that just add up. If they can get recumbents into the sub twenty pound range with three chains on them, there is no reason why the Silvio shouldn't be in the range, even with suspension.
But.... Who am I kidding? I can take way more off the engine in a month than you could shave off the Silvio at any cost.
Mark
I am sure this is all down to the rear elastomers being far too hard, the ones fitted are desined to work at a ratio of, tiny elastomer movement to large wheel movement, but are operating in a 1:1 situation on the Silvio. I have tried drilling 9 vertical 4mm holes through both elastomers to soften them and although this has improved the situation slightly, it's not enough yet to recomend the mod. I am currently looking for a totaly different material and will report back if it works.
Stuart.
UK.
John Tolhurst
Zen MBB Master
Sounds like a useful thing to explore Stuart. The elastomers - the whole suspension set up actually - is lifted from a regular bike and it is good to see this feedback. As I mentioned in the post on tire choice, my preference on the roads around here is to have the bike set up quite firm. It seems to be more responsive that way. Softening the rear elastomer by altering its shape is a really useful step. If we can get a better shape nutted out, I'll have it produced and sent out free to every Silvio owner.
Your initial thought to have longitudinal holes drilled to different depths, so allow partial collapse with only the rider's weight and provide that floating feel that should reduce the buzz, then when this short section is collapsed, the response rate gets much more stiff. That led me to think it could be done as a stack of disks of the same thickness, but different diameters. The narrow diameters adding up to softness, the larger diameters adding up to firmness. We could swap them in and out to generate different response rates and so tune it in?
John Tolhurst
Zen MBB Master
You are probably right, however both the tooling costs and production costs for carbon seat stays would be around twenty or thirty times that for a rising rate elastomer done with swappable disks and that is without the cost of my time to design them and supervise the production. While the improved elastomer could be issued to everyone at no charge.
MrSteve
Zen MBB Master
That's pretty much how Norton tuned the Isolastic system in it's Commando, Combat and Interstate models.
This was a rubber vibration isolation system that kept the engine's vibrations isolated from the rest of the frame.
Norton used different widths of the elastomer suspension for each model motorcycle and then shimmed them to a particularly critical tolerance.
It worked.
My old Commando Interstate was the smoothest motorcycle I've ever ridden.
For the Silvio, think of the different weights that the 'motor' powering the bike comes in.
The isolastic system worked very well for Norton and (in a similar form) continues to work for Harley and Buell.
It ought to work fine for Silvio.
-Didn't the original Austin Mini Cooper use elastomer springs in it's suspension?
-Steve
Mark B
Zen MBB Master
johntolhurst wrote:You are probably right, however both the tooling costs and production costs for carbon seat stays would be around twenty or thirty times that for a rising rate elastomer done with swappable disks and that is without the cost of my time to design them and supervise the production. While the improved elastomer could be issued to everyone at no charge.
True, there's no denying that. Honestly, I was thinking more of an aftermarket upgrade, or revision for possible future generations of Silvios. It would be neat to see how it compares, anyway.
Mark
John Tolhurst
Zen MBB Master
Yakmurph, that is a great observation, thank you.
Suppose the disks were 3mm thick. And say 3 at 13mmOD, interleaved with 4 at 20mm OD. Something like that.
Suppose the disks were 3mm thick. And say 3 at 13mmOD, interleaved with 4 at 20mm OD. Something like that.
It's a great idea John, but we need to come up with a way to stick all those discs together without having to have a bolt run through the middle.
How about the very simple:-
http://www.antivibrationmethodsrubber.co.uk/html/bump_stops.html
See the 'Bullet shaped bump stops'
No bolt inside the rubber, so maximum suspension travel and bullet shaped, so rising rate.
If necessary, it's hardness could be reducd by drilling a single hole (of differnt diameters for different weight riders) straight through the nose of the bullet (a dum dum bullet, if you like).
(Oh, and yes, all the old Minis had rubber suspension (exept a very few which had hydro-elastic suspension) and drilling holes in the rubber was a recognised way of softening the suspension.)
Stuart.
John Tolhurst
Zen MBB Master
Oh, yes, the bullet is nice one. I might soon get a knife out and carve something up. !!Flasharry wrote:It's a great idea John, but we need to come up with a way to stick all those discs together without having to have a bolt run through the middle.
How about the very simple:-
http://www.antivibrationmethodsrubber.co.uk/html/bump_stops.html
See the 'Bullet shaped bump stops'
No bolt inside the rubber, so maximum suspension travel and bullet shaped, so rising rate.
If necessary, it's hardness could be reducd by drilling a single hole (of differnt diameters for different weight riders) straight through the nose of the bullet (a dum dum bullet, if you like).
Stuart.
MrSteve
Zen MBB Master
Yes...it'd almost have to be a modular system, scalable, rugged, simple.
Yet easily adaptable to widely varying rider weights.
Sticking with the elastomer suspension system probably makes more sense than my latest
Rube Goldberg idea.
-Involving a few meters of bungee cord, sheaves, dead eyes, fair leads, cam cleats, dolphin striker and the associated nuts, bolts and washers to install it all....
:twisted: :lol:
-Steve
Doug Burton
Zen MBB Master
Showing my age here...
Back when we were racing sports cars, Koni (shock absorber company) used an active bump stop they called a "Silasto" to control the last inch of suspension travel. It was a silicone cone with a reverse-conical inner diameter. This made the car come to the end of its suspension travel in a controlled and calibrate-able manner, working like a high-rate progressive spring.
These are apparently still available:
http://secure.chassisshop.com/partdetail/70.34.54.000.0/
Also,
http://www.ground-control-store.com/products/description.php/II=10/CA=1
Since Koni makes shocks for anything with wheels, we should be able to source a silasto that will fit the existing locating stud on the Silvio frame, or sleeve the stud to adjust the diameter.
Best,
Back when we were racing sports cars, Koni (shock absorber company) used an active bump stop they called a "Silasto" to control the last inch of suspension travel. It was a silicone cone with a reverse-conical inner diameter. This made the car come to the end of its suspension travel in a controlled and calibrate-able manner, working like a high-rate progressive spring.
These are apparently still available:
http://secure.chassisshop.com/partdetail/70.34.54.000.0/
Also,
http://www.ground-control-store.com/products/description.php/II=10/CA=1
Since Koni makes shocks for anything with wheels, we should be able to source a silasto that will fit the existing locating stud on the Silvio frame, or sleeve the stud to adjust the diameter.
Best,
JonB
Zen MBB Master
copy (or license) the Moulton front suspension
Hi
What about copying or licensing if they have a patent, the Moulton front suspension. It seems much softer than what my freerider has, and possibly what a silvio has.
Further more i think that the cruzbike kit might just possibly be fitted to the new? triangle frame from Moulton. Look at Moulton AM18 pictures for clues.
Hi
What about copying or licensing if they have a patent, the Moulton front suspension. It seems much softer than what my freerider has, and possibly what a silvio has.
Further more i think that the cruzbike kit might just possibly be fitted to the new? triangle frame from Moulton. Look at Moulton AM18 pictures for clues.
Okay, now that I own a silvio, I've got a few wish-list items for future iterations.
The seat bottom could mimic the euromesh2 design
http://i10.photobucket.com/albums/a139/nomo4me/IMG_0322.jpg
which makes straddling the seat and reaching the ground more comfortable when sitting on the bike at a stop. Plus it would help with the problem I'm noticing where my upper hamstring touches the edge of the seat every pedal stroke. Doesn't hit exactly, just touches with a slight pressure every stroke.
A thicker skirt under the headset could help to reduce chances of a dent in shipping causing it to scrape the fork neck.
A narrower front chainstay would be nice if possible. I have a relatively toe-out posture, and artificially straightening my feet puts a lot of twisting pressure on my knees. In my natural toe-out stance my heel strikes the chainstay occasionally. It's really not too often that this happens, but every mm helps.
And finally the rear suspension. I've posted before about how I think the entire frame is heavier than necessary because it is having to cope with the lack of support from a rear triangle. On top of that the rear suspension gets in the way of most attempts to put a seat bag back there, leading to a traditional bike rack and bag for even more weight. And all of that weight penalty is being paid for a rear suspension where the ride quality is on par or slightly less plush than my strada with euromesh.
I'm a big fan of the mechanics of the front half of the bike, but the rear half takes a design that could be a market leading elite weight for a quality recumbent, and drops it squarely in the middle of the pack. Setup to ride, my silvio is about 1/2 pound heavier than my strada (which has rotor cranks).
- Mark
The seat bottom could mimic the euromesh2 design
http://i10.photobucket.com/albums/a139/nomo4me/IMG_0322.jpg
which makes straddling the seat and reaching the ground more comfortable when sitting on the bike at a stop. Plus it would help with the problem I'm noticing where my upper hamstring touches the edge of the seat every pedal stroke. Doesn't hit exactly, just touches with a slight pressure every stroke.
A thicker skirt under the headset could help to reduce chances of a dent in shipping causing it to scrape the fork neck.
A narrower front chainstay would be nice if possible. I have a relatively toe-out posture, and artificially straightening my feet puts a lot of twisting pressure on my knees. In my natural toe-out stance my heel strikes the chainstay occasionally. It's really not too often that this happens, but every mm helps.
And finally the rear suspension. I've posted before about how I think the entire frame is heavier than necessary because it is having to cope with the lack of support from a rear triangle. On top of that the rear suspension gets in the way of most attempts to put a seat bag back there, leading to a traditional bike rack and bag for even more weight. And all of that weight penalty is being paid for a rear suspension where the ride quality is on par or slightly less plush than my strada with euromesh.
I'm a big fan of the mechanics of the front half of the bike, but the rear half takes a design that could be a market leading elite weight for a quality recumbent, and drops it squarely in the middle of the pack. Setup to ride, my silvio is about 1/2 pound heavier than my strada (which has rotor cranks).
- Mark
currystomper
Well-Known Member
In a different thought
what about a folding cruz based on this bike.
Note the full road elastomer suspension
Hey thats my other bike that I commute on :lol: it not a clean as this now though!!
or you could tidy up the whole long bike cruz idea that floating around the web site, seen one idea where the stoker at the back powers the back wheel (well weird)
Brian
what about a folding cruz based on this bike.
Note the full road elastomer suspension
Hey thats my other bike that I commute on :lol: it not a clean as this now though!!
or you could tidy up the whole long bike cruz idea that floating around the web site, seen one idea where the stoker at the back powers the back wheel (well weird)
Brian
