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Discussion Starter · #1 ·
So on sizing chainstays to length and taking into consideration tube butting, tire clearance, bend of stay, and beltring clearance issues.
Is there a "best" way to approach this? Is there a sweet spot for the bend in the stay? (when the axle/do is completely open/ completely closed/ middle?

No reason not to double check my thoughts with the best!

Here are the specs:
  • 26x18 Oval/12° Bend HOX5CS (True Temper chainstays)
  • Ride Goals: Singlespeed Beltdrive (with blackcat swinger dropouts)

What I want to end up with:
  1. 440 CS length (min) This is what the picture is showing.
  2. 2.1 Tire (so I went with 56 mm width in the drawing ...then added the 5mm MIN of tire/stay clearance to each side as Walt from Waltworks pointed out on a blog. By the way....same Walt on this forum right? :thumbsup:

When in doubt...draw it out. (was actually pretty fun to do. :)
There are 2 pictures.
One shows the right chainstay HIGHER/CLOSER on the BB (this put the 'bend' in the stay closer to the actual tire when the dropouts are completely "closed.' Not good for chainring clearance. BUT I could technically lightly crimp the inside of stays and have more clearance overall.....(hmmm)

The other picture has the chainstay LOWER/FURTHER AWAY on the BB drawing (hence dropping the bend in the stay lower in the stay. From the pic this would also allow better beltring clearance (have a 39 tooth ring ready to go)

Thanks in advance. Only reason I ask is there was a post on Frame Forum and the poster seemed to elude that cutting/mitering the DO chainstay side was correct.

Thanks in advance.

Cheers.
 

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illcomm33 said:
What I want to end up with:
  1. 440 CS length (min) This is what the picture is showing.
  2. 2.1 Tire (so I went with 56 mm width in the drawing ...then added the 5mm MIN of tire/stay clearance to each side as Walt from Waltworks pointed out on a blog. By the way....same Walt on this forum right? :thumbsup:

Cheers.
did you draw the tire with the square end at the outer radius or at the widest point radius?

If it is the former you have room to move the stay closer to the tire.
 

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It looks like your almost there........judging from the first drawing (the one on top) in which it seems you will be cutting the CS from both ends. As far as tire clearance goes, you just want to make sure that the bend corresponds to the widest point on the tire.......being that this will be a belt drive (I've built none).....have you considered a wider BB for better chain-ring/CS clearance? Good luck and by the way those True-Temper CS are real nice, I've used them a few times and they braze/work well........:thumbsup: .
 

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Discussion Starter · #7 ·
Chainstay follow up: Thanks!

TimT said:
http://www.g-boxx.com/e-carbondrive.html

You really want to draw in the front ring. One of the big problems with belt drive is the cogs and rings are so wide. From the picture you posted it looks to me that the ring (if you use a 46 which I recomend) will cut through your stay.The above web site as more tech info then the offical Gates one.

Tim
Thank you everyone for the quick and detailed responses. The MTBR community is truly amazing and I can't thank you enough for the guidance. Here are a few follow ups and explanations for my thoughts.

Does everyone draw chainstay diagrams? I was stumped on how to approach the stays and figured drawing is the best way to go. So far I am really happy I did. At least I have a fighting chance to miter and cut somewhat right. :)

1) Drawing in the belt ring: (As I can see this is a must now!)
Last night I reviewed my Spot 29er (XTR 970 Crankarms with a 46 X 28 belt) and attempted to calculate the distance from the BB and ring (It appears to "hang over" the BB plane) but couldn't' dial in a solid spec so instead of guessing I skipped it. Will attempt again this evening. Anybody have a spec for how much it hangs over the BB plane?

2) 39 vs 46 belt ring?
-All the new Spots come with the 39 so I figured it was the way to go. Smaller ring, better clearance. I have heard stories of "less contact patch" on the rear cog could lead to skipping. As anything with the belts I chalked it up to set up. Legit? I would keep the 46 on my Spo but see the clearance even more of an issue.

3) 440 mm stays:
- I again pulled this spec from my Spot Longboard and figured that I would really never use the 440 mm setting because I would have to tension the belt...didn't want to go shorter. Also Waltworks mentioned that 435 was pretty much the shortest comfortable length.

4) Chainstay support bridge. TO use or NOT to use. (new question)
- There appears to be several builders out there not using that chainstay brace. I like the look of a clean rear end....and thought about also not using one. Good idea or bad? Flexy?

5) The radius of the square tire.
- Figured I would draw it square...that way when the rounder tire is in the stays I already have more room.

Hope everyone is having a great day (and in Austin for NAHBS!)
 

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Call Steve at SpotBikes about the new CenterTrack belt drive stuff. He may have a technical drawing to send you. They have MILES more chain stay clearance than the currently available setups. If there's a down side, moving the belt out to the right reduces clearance on the seat stay...super curvy seat stays won't work at all for specific applications.
 

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http://forums.mtbr.com/showthread.php?t=617192
check this thread out on my first belt drive conversion. Learned quite a lot.
the belt poping is pretty much do to the belt riding up the cog and then snapping down. So what can fix this. Very strong stays is the first one. I filled my test frame with expandable urathane foam worked pretty good but didn't totaly get rid of the popping in my case. Shortening the stays will stiffen them up too. On the new frame I'm seriously considering going to 650B in the rear 29 in the front. Adjusting the pitch/yaw of the belt line. Slider or swing style drop outs are best for this you can tune the left/right angle of the axle.Belt tension. at first I had so much tension on the belt the bearings on the hub and BB were dragging. Not the way to go in my opinion as this can cause warn out parts. The Cricket belt tension devise that Gates sells for belt drinve is really a restickered automotive one they sell. the bike one costs $45 the car one $15 rip off and doesn't really work. Also i blame the over tension on my first belt stretching. Yes they do and will stretch. Increase the diameter of the cogs, this gives a better wrap around the ring/cog its harded for the belt to jump.
The best thing to get for the popping is a Rohloff Belt Drive "snubber" There is a picture of it in my thread. It just works.

Tim
If your going to NAHBS I'll have my first belt drive bike with me.
 

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illcomm33 said:
The radius of the square tire.
- Figured I would draw it square...that way when the rounder tire is in the stays I already have more room.
Do your best to draw it in "real". If you leave it square, you may push your stays outward for no real benefit, and then you'll be killing yourself trying to find room for the chainring. When you lengthen the stays to tension the belt, the tire will move backwards, giving you more clearance to the stays, meaning that the outward pushing of the stays is kind of compounded, giving you clearance you don't need (b/c your tire is farther back) and headache you don't want (b/c you've pushed the stay toward the drive ring).
 

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An excellent thread...

Tim, your thread is awesome. And it's what finally convinced me that I will never bother with a belt drive (for myself, that is). By the time you've got beefy chainstays, some way to split the frame for the belt, all the parts, and a snubber, you've got a system that is heavier and less functional (not to mention more expensive and finicky) than a chain drive.

FWIW, Illcomm - I would use something beefier than the HOX5CS. Deda 1.0 s-bends, maybe (they're not light, but they're strong and good for tire clearance purposes). You want *beefy* for the chainstays to keep the flex to a minimum. From what I'm told the 39t sprocket is fine, but the smaller rear cogs have a lot of skipping problems, so if you want more high-gear flexibility, I'd design around the 46.

-Walt
 

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illcomm33 said:
The radius of the square tire.
- Figured I would draw it square...that way when the rounder tire is in the stays I already have more room.
Do your best to draw it in "real". If you leave it square, you may push your stays outward for no real benefit, and then you'll be killing yourself trying to find room for the chainring. When you lengthen the stays to tension the belt, the tire will move backwards, giving you more clearance to the stays, meaning that the outward pushing of the stays is kind of compounded, giving you clearance you don't need (b/c your tire is farther back) and headache you don't want (b/c you've pushed the stay toward the drive ring).
 

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Discussion Starter · #13 ·
TimT said:
http://forums.mtbr.com/showthread.php?t=617192
check this thread out on my first belt drive conversion. Learned quite a lot.
the belt poping is pretty much do to the belt riding up the cog and then snapping down. So what can fix this. Very strong stays is the first one. I filled my test frame with expandable urathane foam worked pretty good but didn't totaly get rid of the popping in my case. Shortening the stays will stiffen them up too. On the new frame I'm seriously considering going to 650B in the rear 29 in the front. Adjusting the pitch/yaw of the belt line. Slider or swing style drop outs are best for this you can tune the left/right angle of the axle.Belt tension. at first I had so much tension on the belt the bearings on the hub and BB were dragging. Not the way to go in my opinion as this can cause warn out parts. The Cricket belt tension devise that Gates sells for belt drinve is really a restickered automotive one they sell. the bike one costs $45 the car one $15 rip off and doesn't really work. Also i blame the over tension on my first belt stretching. Yes they do and will stretch. Increase the diameter of the cogs, this gives a better wrap around the ring/cog its harded for the belt to jump.
The best thing to get for the popping is a Rohloff Belt Drive "snubber" There is a picture of it in my thread. It just works.

Tim
If your going to NAHBS I'll have my first belt drive bike with me.
I do remember reading that epic story! That is crazy....It was inspirational because of the effort to say the least.
The foam idea is also a great idea. How much was the weight penalty? I thought about using something like that to fill in behind the inevitable dimple I will need to put on the driveside stay.
Yeah...I got hosed on the "cricket" when it first came out. It wasn't well known at the time it was the same one as the auto with a cute sticker over it. Spent the $40 but have been happy to have something to guide during tensioning.
Just when I felt like I knew a fair amount about belt drives out comes this SNUBBER deal. Never even heard of it. Reviews seem to back it up that it is a must. Where do you find that thing at?
 

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Walt
Once I got the bugs worked out it worked great. I guess thats why I'm building another. I took it to Oak Mt. and rode it not one pop. Big climbing there. Got maybe 750 miles on it now. Awsome in the mud.

illcom
You can get a snubber from the Rohloff dealer here in the US. I think it is Ride Monkey. Its not on the web page you have to e-mail them.Screws right on to a der. hanger. If you use a Alfine you'll have to extend the arm. The weight penalty on the foam??? Not much seeing as its mostly air.

See you guys later getting off work and packing up. Leaving in the morning going to Austin/NAHBS.


Tim
 

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Discussion Starter · #15 ·
Beltring drawn in...definitely helps see the big picture (more pics attached)

Great advice to get the beltring specs and get it drawn in. It helps!
For anyone else who wanted to know here is what I determined.

- Belt ring overlaps driveside external BB cup by approximately 3.5 mm. (CK hub with 2 of those skinny nylon crank arm spacers installed on the xtr arm (not the bb cup spacers)
- 39 tooth belt ring has a 138 mm diameter and is 13.2 mm thick/wide
- 46 tooth belt ring has a 169 mm diameter and is 13.2 mm thick/wide.
(clearance of chainstay of a difference of 15.2 mm!) The pics show the 15.2 added on to each side of the ring with - - - - -

Walt,
I contacted Joe Brengheli for the Deda chainstay...he won't get any CS double bends until April. What are your thoughts on a substitute? Anybody out there have a hook up for these deda 1.0 chainstays? You know your stuff so if you are saying what I have won't work.... I won't even test it.
 

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Discussion Starter · #20 ·
Thanks

TimT said:
Just one quick correction on were to get the snubber. Its Cycle Monkey not Ride Monkey.

Tim
Thanks for the update. Since I will be using the Black Cat rockers (no der hanger) it looks like this gadget won't work out for me.
On a good note..just bought the Deda S bend stays that Walt recommended. FedEx better get here quick!
 
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