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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Improved S40 suspension? /cgi-bin/YaBB.pl?num=1208005080 Message started by barry68v10 on 04/12/08 at 05:58:00 |
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Title: Improved S40 suspension? Post by barry68v10 on 04/12/08 at 05:58:00 After exploring a few different options, I've begun pondering an alternate solution and I want some feedback. I've considered moving the lower shock mount back and down to co-locate it with the rear axle. This would allow a MUCH LONGER shock, and I think you could gain a bunch of extra suspension travel and "dial-in" capability. Anybody thought of or tried this? Good idea, dumb idea? Thoughts? |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 06:19:10 I don't think that would give any longer travel.Wouldn't putting a long shock do the same thing .You would be raising the seat height either way. |
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Title: Re: Improved S40 suspension? Post by LANCER on 04/12/08 at 06:42:34 My sporty have the lower rear shock mounts co-located with the belt/chain adjusters at the very end of the swingarm, just behind the rear axle. It does allow a longer shock (12" at present) and still has a lowered look. For a stock look a 14" shock is required. |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 08:00:00 yep, the geometry would give it longer travel. moving it back will make the shock seem stiffer. but laying it down will take some of that away. It will take some working out to get it right. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 09:04:04 The shock would have a longer travel but the swing arm wouldn't.The straighter up the shock is would be stiffer the way I see it. The flatter it is the would be a leverage,which would make it go up and down easier.I think i see it the opposite that you do. |
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Title: Re: Improved S40 suspension? Post by demin on 04/12/08 at 09:08:42 The swingarm swings in an arc.The shock needs to be inline with that arc. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 09:32:40 Yes the swing arm swings in an arc,put the shock doesn't have to be inline with the arc. |
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Title: Re: Improved S40 suspension? Post by Onederer on 04/12/08 at 10:35:00 You'll run outa travel when the tire hits the fender. To get more travel, the bike will have to set higher. Modern link type suspensions have a shock with relativley short travel, but the linkage allows the actual travel to be more than the shock. The progressive 412's seem to be the way to go. Air shocks would be great, but I don't know if they'd clear the strut on the right side. I think the lowering kits for most crusiers just move the lower part of the shock back, like you'r wanting to do, unless someone spends the $$ for shorter shocks. Bottom line, to get more travel from your rear suspension, you'll have to raise the bike. If you wana go 60mph over speed bumps, then just get a DR650. From the kitchen of goodness, the ceramic throne will follow. |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 12:15:44 For illustration: http://hometown.aol.com/camchainclub/images/rear%20suspension.jpg The greater the angle of the shock to the rear axle travel, the less it will travel. The further out along the swing arm, the less force the shock will see. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 12:53:14 You would have to use a longer shock if you did that you would have the same travel,In order to get more travel you have to raise the bike. |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 16:06:21 Engineering 101: Balance of forces. Let's assume the swingarm is horizontal... For a certain belt length, the axle is 19.5" from the swingarm pivot. For the axle hold the rear up, X pounds must be supported by the axle. We have a spring and a shock absorber to keep the fender off of the tire. The shock mount on the swingarm is 15.25" from the swingarm pivot. And a force Y is needed to keep the bike up. How do you figure out X and Y? By balancing the forces about the swingarm pivot. 19.5 times X is equal to 15.25 times Y So Y is 1.28 times X Follow? Now for the fun part, the above calculated the forces assuming the force on the axle pushed straight up and the shock pushed straight down. Well guess what? the shock pushes at an angle. Der wat dus dat meen? Only some of the force on the shock/spring is applied to the axle. Take a rough measurement of the shock to horizontal, plug that into your calculator and push the sin button. The sin of 51° is .78 1/.78 is 1.28 What a coincidence, that the same ratio of the shock to axle force. 1.28 times 1.28 is the force required by the shock to keep the tire off of the fender. 1.64 For every pound on the wheel, 1.64# is on the shock/spring. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 17:10:35 Let us know how it rides when you get that done,verslagen |
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Title: Re: Improved S40 suspension? Post by steely on 04/12/08 at 18:13:16 Verslagen is correct. It would require a stouter spring because the increased leverage of the swing arm against the shock would apply more force. I ran into that problem when I lowered the GS. In lowering the rear mounting point, I changed the angle of the shock. Even with a shock designed for a fully dressed Goldwing, I was bottoming out. I had to go back to the original shocks until I could get the new fender (that sat higher) mounted. |
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Title: Re: Improved S40 suspension? Post by demin on 04/12/08 at 18:17:51 steely.He just doesn't get it.I gave up. :-? |
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Title: Re: Improved S40 suspension? Post by steely on 04/12/08 at 18:22:43 Every once in a while I figure that dead horse just will get up... |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 19:14:43 7B7075752F2E190 wrote:
I didn't start this. I'm in it just as a mental exercise. Maybe I'll get some good tips rear end geometry. ;D You don't need to go 'mental' on us. You don't believe it can be done, fine, say what experience you got. I'd like to hear it. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/12/08 at 19:36:51 Most snowmobiles have 2 or 3 holes on the rear suspension to change the angle of the shock .my first snomobile 36 years ago had it,I know what changing the angle does. |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 20:52:35 4B485B5B501F115F1819290 wrote:
4B485B5B501F115F1819290 wrote:
4B485B5B501F115F1819290 wrote:
Bill, were the added holes on the swingarm or the top mount? |
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Title: Re: Improved S40 suspension? Post by barry68v10 on 04/12/08 at 20:55:51 Great fellas! This is the kind of lively debate I like to see around here. Gets the ol' mental juices flowin'. ;D Bill, one of the main reasons for moving the shock mount back is to increase my selection of shocks and springs. Once you get out to 14-15" shocks and greater (eye-to-eye) your selection of both improves and prices seem to drop slightly. You can even start to look at dirt/circle track car parts... I've been through this on my dirtbike. Except in reverse, kept blowing out shocks, and with an 1800 lb/inch spring, the darn thing was still too soft! To correct the problem I added a 650 lb/inch spring. (Yes, I now have two springs on my mono-shock dirtbike.) Which, would have been too much if in-line with suspension travel (the spring was what I had on-hand), so I moved it 30 degrees out (out of the radius angle.) This cut the effect enough to be perfect for me and my style of trail-riding. If I moved BOTH upper and lower shock mounts rear-ward, I would expect a MUCH STIFFER ride with the same shocks. By only moving the bottom mount back, I expect the ride to soften with the same shocks and springs. If we all agree on these points, we can REALLY have some fun with Verslagen and express all the equations that show how this works... ;D On a side note, a PHD Mechanical Engineer and I headed down the wrong path with this problem until my first "test" and we saw the error of our ways...my first test left my dirtbike sitting with the fender ON the rear wheel. (To be fair, my Mech E friend works in aircraft design and doesn't enounter problems like this on the job.) |
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Title: Re: Improved S40 suspension? Post by barry68v10 on 04/12/08 at 21:33:39 [quote]Yo, Barry haven't heard from you, doing some practical studies? Sorry, wife put me to work yesterday and today... 4B485B5B501F115F1819290 wrote:
I assumed when you "bottom out" your reaching the end of suspension travel in the shock but not necessarily the mechanical limits of the swingarm or tire-to-fender clearance. Is that false? I do intend to increase the ride height as well. 4B485B5B501F115F1819290 wrote:
I don't like the bone-crushing ride the stock suspension gives. I'd like to see more stock "sag" so the tire could react better to potholes, bumps, etc. Also, I want to be able to change on-the-fly based on the type of riding I'll be doing. There are auto coil-over shocks I've been eyeing that have compression-biased valving. You can get them from 11.25" up to 24.5" with up to 9 inches of travel. You can also externally tune rebound and compression damping as well as spring preload. You can get springs for them in anything from 95 in/lbs to 450. I find myself turning to auto technology when possible because of the higher demand/availability/selection. As I've stated before, I can't help it, I like to "tinker." ;D When it's all said and done, I might just go with some Progressive 412 shocks in 12" or 12.5" and be done. Especially if I can't figure out how to make this work before I drop the necessary $. But the mental gymnastics keeps me on my toes, and who knows? I might find a break-through with one of these hair-brained schemes the rest of you can benefit from. ;D |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/12/08 at 22:24:31 2E2D3E3E357A743A7D7C4C0 wrote:
I do stress in aircraft duct work, so I'll cut him some slack. Mainly cause I know how high his thinking can be and basic stuff just doesn't enter the picture. What you don't use, you forget. I suspect damping is what you need to play with most. |
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Title: Re: Improved S40 suspension? Post by bill67 on 04/13/08 at 03:22:24 I want hold you guys youth and inexperience against you, but my bike rides must better than stock.I'm very happy with the progressive shocks.The seat feels good,I didn't have to raise the front of the seat,I can move around on the seat I'm not locked in one position.By what I've heard here the single seat must be better than the 2 piece seat. |
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Title: Re: Improved S40 suspension? Post by demin on 04/13/08 at 06:01:52 Did you change the angle of the shocks or did you just change shocks? I think aviation engineering qualifies a little better than some old farts opinion about his 30 year old sled!Just change your seat that'll fix everything. |
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Title: Re: Improved S40 suspension? Post by verslagen1 on 04/13/08 at 08:13:56 6E6D7E7E753A347A3D3C0C0 wrote:
So you got a back up plan, which is what bill did plus a good seat. fleabay had a swingarm not to long ago, did you pick it up for mod's? |
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Title: Re: Improved S40 suspension? Post by barry68v10 on 04/13/08 at 17:36:55 Good thought Verslagen! I didn't see the swing arm, but I'll start looking to see if I can get something to tinker with. ;D |
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