Karl's V20 variable seat angle solution

[Karl42]

Which has me thinking looking at the specs of the hinges why not use a second one instead of the metal hasp? Then rather than have the strut central and over the frame member, could have one either side what wouldn't impede on the original seat angle??? I should rig up a test thing to see if it can work...in miniature of course.

The 5 inch metal hasp feels a bit overbuilt for this, but it provides a lot of stability and feels very solid. I also have the original 4 inch hasp from Sea-Sure that @Pcmousley used for his project. It weighs 55 grams. The one I use currently has a 5 inch arm and weighs 85 grams. The Sea-Sure one is a bit flatter and would probably still be strong enough, but the longer one just fits perfectly in the existing hole in the frame where the screw for the perez clamp is. The shorter hasp (or other hinge) would have to sit a bit more forward, just above where the frame has a big hole. I thought about constructing something with the alu plate to mount the hinge in the hole, but the current solution is just so much simpler that I went with this one for now.

Using a second carbon hinge for the seat support sounds interesting, but sounds like much more effort, because the carbon hinge itself is very small, so you would still need to make the strut (or struts) out of something. If you make a up a test rig for this I would be interested to see it.

I am more than reluctant to cut my seat...to which I think I'd like to get a spare save ruining the original??

I hear you. I actually found and bought a used V20 seat for this reason, so that I have a spare in case this project doesn't work out (and then I still had it lying around for a long time before I actually got the courage to cut my seat - which turned out to be much easier than I had feared).
Given the number of riders who replaced their stock seat with something else, you'll probably find one of those seats for sale here in the forum if you ask for it.

 

[cpml123]

Thank you for the detailed description,I've been following the project for a while. I realise the carbon hinge is an Australian product, so nice an local to me..Which has me thinking looking at the specs of the hinges why not use a second one instead of the metal hasp? Then rather than have the strut central and over the frame member, could have one either side what wouldn't impede on the original seat angle??? I should rig up a test thing to see if it can work...in miniature of course. I am more than reluctant to cut my seat...to which I think I'd like to get a spare save ruining the original??

I think you will find there are many V20 or S40 seats lying around in our garages if you ever need another one. I have 2 because I changed the seats to Thor seats.

 

[Karl42]

This weekend, I rode a Brevet covering 400 kilometers (250 miles) with 3,500 meters (11,500 feet) of elevation gain. The seat adjustment worked very well overall and made the extensive climbing on this tour significantly easier. There are still a few minor improvements I’ve thought of, but the basic principle works very well.

When the seat is raised, a very stable triangle is formed by the seatback and the hasp supporting the seat, which transfers the pressure on the seatback into the frame. This allows me to generate significantly more power on the pedals than in the horizontal position, because in the upright position, my legs can now work like they would in a leg press. In addition, the heart is now much higher than the legs, and that also seems to have a positive effect on power output.

One downside is that in the upright position, I’m now sitting on my glutes, which leads to pain there over time (“recumbent butt”). To counter this, it helps to switch between the upright and reclined positions frequently to relieve the glutes every now and then. Still, by the end of the ride, my butt was pretty sore because I’m not used to it yet. But that was after a 400-kilometer ride with a lot of elevation gain. On normal routes, that shouldn’t be a problem.

Overall, I’m thrilled with this seat adjustment and don’t want to ride without it anymore.

 

[IyhelM]

I’ll rest my case until next weekend and my own 400 brevet but part of the recumbutt is probably due to muscle groups being used slightly differently; switching from the Silvio to the Létrange and its less reclined seat, I feel discomfort in the glute but I still don’t know (after only 350 km) how much of that is muscular adaptation and how much position (which should then be adjusted and improved).

In any case, I think we can declare your system proven and tested!

 

[Karl42]

I still need to improve the back plate of the seat, where the hasp pushes and slides against. My provisional solution consisting of some strips of plastic glued on with rim tape disintegrated fairly quickly. This prevented the lever from pulling the hasp back, because it would get caught in the torn tape. On the upside, I discovered that I can just reach behind my back and push the hasp back with my hand, so the lever is not really needed and could be left out for a minimalist build, although using it is more comfortable.

So next I will try to bend the alu plate to follow the curve of the seat in order to have a more stable sliding surface for the hasp.

 

[sixty-six]

I still need to improve the back plate of the seat, where the hasp pushes and slides against. My provisional solution consisting of some strips of plastic glued on with rim tape disintegrated fairly quickly. This prevented the lever from pulling the hasp back, because it would get caught in the torn tape. On the upside, I discovered that I can just reach behind my back and push the hasp back with my hand, so the lever is not really needed and could be left out for a minimalist build, although using it is more comfortable.

So next I will try to bend the alu plate to follow the curve of the seat in order to have a more stable sliding surface for the hasp.

I think that's why even though it's more hassle I am leaning towards two hinges wither side of the frame member, which some kind of struts using the holes for the bottle cages to fit onto??? so there is no possibility of damage to the seat back...ideas ideas...need to bodge something together to test...would be great to get another seat to experiment , but suspect postage to Australia will not be viable...the hinge and join on the seat will be the same irrespective of the lifting, fitting method...possible even use air type struts from a car hatch back??? will investigate weight capacities.....mmmm

 

[Joe Riel]

Greg's solution to changing the seat angle might be a simple way to determine how effective it is, without risking damage to the seat (i.e. making it variable).

 

[sixty-six]

just realised that a dropper post would work perfectly, however fitting it would require some major surgery! maybe I should get a spare frame as well as a spare seat to experiment with ?

 

[Karl42]

just realised that a dropper post would work perfectly, however fitting it would require some major surgery! maybe I should get a spare frame as well as a spare seat to experiment with ?

If you go back to the original thread from @Pcmousley linked to from the start of this thread here, you'll find that he originally started with an MTB adjustable seat post and then concluded that this doesn't work well.
Notwithstanding the challenge of fitting it, a dropper post would probably be much heavier and more expensive than the hasp that weighs 50-80 grams and costs about 6 Euro / 7 USD. Moreover, the hasp is trivially easy to fit to the V20 without any modifications to the frame. I also really like that it raises the seat without requiring pushing the lever. So when I'm riding and suddenly I need the extra power output because there is an unexpected hill around a corner, or I want to sit upright because of stopping at an intersection, I simply lean forward and the seat raises instantly. All solutions that lock the seat in the lower position would first require to unlock it manually.
In any case, the solution presented here can certainly be improved, but I think it will be difficult to beat it in terms of weight, cost, and simplicity (for both installation and operation).

 

[Karl42]

Today I made a protector cap for the hasp so that there is no longer steel grinding against alu or even carbon fiber. I first wanted to order a plate made out of POM-C, but then I realized that an IKEA chopping board can deliver something similar for a fraction of the cost. The IKEA LEGITIM chopping board is made out of Polyethylen and costs less than two Euro (https://www.ikea.com/de/en/p/legitim-chopping-board-set-of-2-white-70556703/). In any case, I didn't buy this but used one I already had.

I first cut a corner out of this with my carbon cutting saw, and then I used my Dremel with a 2 mm drill to mill a rectangular hole that matches the tip of the hasp. The whole process took about 20 minutes. Now the cap sits firmly on the hasp and probably won't even need glue or screws to be secured, but I might use something like that anyway. This material is softer than POM, but I hope that it will last for quite a while. And even if it wears out eventually, I still have enough material left to make more very easily.

The pictures show a 4 inch hasp with an arm length of 105 mm. The longer 5 inch hasp shown in the videos has an arm length of 125 mm. It works, but raises the seat a little bit too high for me and makes the bike feel cramped in the upright position. The 4 inch hasp with the protector now has an arm length of 114 mm, so I hope that works well.

 

[IyhelM]

I’m sure there is a Pinterest page or other to showcase all the uses people found for IKEA chopping boards over decades.
20 years ago I used to cut disks out of them to make street hockey pucks!

 

[sixty-six]

You are so right...the struts and dropper post are heavy and require major surgery....Larry has already offered me a spare seat or two..and the hinges are a local product...still tempted to use some kind of kevlar/carbon hasp..but initially will of with the metal one...but not for a while..to many other things going on.

If you go back to the original thread from @Pcmousley linked to from the start of this thread here, you'll find that he originally started with an MTB adjustable seat post and then concluded that this doesn't work well.
Notwithstanding the challenge of fitting it, a dropper post would probably be much heavier and more expensive than the hasp that weighs 50-80 grams and costs about 6 Euro / 7 USD. Moreover, the hasp is trivially easy to fit to the V20 without any modifications to the frame. I also really like that it raises the seat without requiring pushing the lever. So when I'm riding and suddenly I need the extra power output because there is an unexpected hill around a corner, or I want to sit upright because of stopping at an intersection, I simply lean forward and the seat raises instantly. All solutions that lock the seat in the lower position would first require to unlock it manually.
In any case, the solution presented here can certainly be improved, but I think it will be difficult to beat it in terms of weight, cost, and simplicity (for both installation and operation).

,