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Message started by Armen on 08/27/16 at 05:08:56

Title: Belt tension with longer shocks
Post by Armen on 08/27/16 at 05:08:56

I'm still dummying up parts. Rearset brackets are on. Rear sets are in place with threaded rod for now. Just seeing how it all lines up.
So, I put on the +2" RYCA shocks along with an 18" rear wheel to pick up the ass end of the bike. Chopped up and braced the swingarm (to make up for the metal removed).Putting it all back together, I figured I'd do a bit of head scratching on the belt tension.
With the longer shocks, there is a fair amount of swingarm droop. Smarter folks than me tell me that 10-15 degrees of droop is a good thing, so that doesn't bother me.
What bothered me was the change in belt tension as the swingarm moved. Eyeballing the shocks, it seems like they have about 1 1/2" of travel. Because they are set partway up the swingarm, that translates to more than that for actual wheel travel.
I took my trusty belt tension gauge, put a jack under the motor, and lifted the real wheel. With about 10 lbs of push the belt moves about 1/4- 3/8".
All well and good.
Then i removed the shocks and lifted the swingarm/wheel to where it would be when the shock compresses 1 1/2".
Yolks! The belt becomes REAL tight.
Worried about killing the belt and bearings.
The belt will become tightest when the centerline of the two pulleys and the swingarm pivot are all in a straight line.
I wasn't even there yet. Just raised the swingarm/wheel as much as they'd move with the shocks bottomed out.
So, I loosened the belt tension a bit with the S/A up. Just to where there was 1/8" of movement with 10 lbs of push.
Shocks back on, and the belt is pretty bloody loose. Like over 1/4" with almost no pressure. And over 1/2" with 10 lbs of push.
Hmm
Wondering what the happy place is between too tight and too loose?

Title: Re: Belt tension with longer shocks
Post by Dave on 08/27/16 at 08:56:30

You have to adjust the belt a bit floppy when you are not on the bike, it will tighten up as you sit on the bike, and when you hit bumps. I prefer to run a bit loose compared to too tight.....I have never experienced any problems from running the belt a bit loose. It has never jumped the teeth, doesn't seem to hit anything, etc.

I would make the swing arm level, adjust for the proper "tight" tension, then put your shocks back on and check the tension....and use that as a guide on what tension you should use.

Title: Re: Belt tension with longer shocks
Post by Armen on 08/27/16 at 09:25:04

Thanks Dave.
I tried checking it at 'level' then looking at it at full extension. Wahoo is it loose. That's why I check at what I thought full compression will be (lower than level).
I'm prob going to go with 1/4" of slack with 10 lbs at tightest point, and just deal with however loose it is when it is loose.
Just bolts on!

Title: Re: Belt tension with longer shocks
Post by Serowbot on 08/27/16 at 16:26:22

...'bout like so...
[media]http://www.youtube.com/watch?v=i2ZsZzTwRyk[/media]

Title: Re: Belt tension with longer shocks
Post by Ruttly on 08/27/16 at 17:26:18

Try all that with a chain that has no stretch , gave up. Made struts to replace the shocks to hold swing arm so countershaft & s/a pivot & rear axle lined up adjusted chain then bought tensioner from Ryca, he said it wouldn't work , then modified it and mounted it to the rear set bracket , works perfect, love my little Miller wire welder !!

Title: Re: Belt tension with longer shocks
Post by Armen on 08/27/16 at 17:45:12

Thanks Ruttly,
Which tensioner?

Title: Re: Belt tension with longer shocks
Post by Ruttly on 08/27/16 at 19:43:26

RYCA online parts store in the bobber parts section
Powell Peralta Editon chain tensioner
Uses a skateboard wheel should be wide enough for the belt too
I didn't take very many pic of the build but I have several of the tensioner mod , must have welded & cut it off 5 or 6 times to get it right
Send you some pics have to find then
Works great even under hard decel & braking which is where it really matters, was upset having to add the weight back on to the bike but it was worth it !

Title: Re: Belt tension with longer shocks
Post by Armen on 08/27/16 at 19:50:39

Thanks!
Feel the same way about weight :(

True confessions:
I drilled the swingarm pivot bolt. ;)

Title: Re: Belt tension with longer shock
Post by Ruttly on 08/27/16 at 21:10:44

But in this case it was a must do

Still haven't weighed it but I'm guessing in the 310 to 320 lbs range

I ride everything like I stole it and being pursued , if I started drilling everything stuff would be breaking , nothing would last

What I built is street legal t/sigs , mirrors , horn and I light as I could get it and still stand up to being abused daily

Title: Re: Belt tension with longer shocks
Post by Ruttly on 08/27/16 at 21:28:25

Armen get ready I'm going to bomb your email inbox found the pics
Pics that they told me it wouldn't work
Let me know if you any ?s

Title: Re: Belt tension with longer shocks
Post by Armen on 08/28/16 at 08:42:18

Ruttly,
Holy crap that was a lot of pics ::)

Seems like it worked out. Buell used a roller tensioner on their later bikes. Seems like a good idea. Not exactly small and pretty, but if having a lot of belt slack is an issue, this seems like a good solution.
Sent a note to RYCA. I'm sure they sell a lot of +2" shocks. Kinda doubt all the folks do a tensioner. Interested to her their answer.
Thanks for taking all the time to send the pics.
Right now I'm just jazzed that I got my dead ass in gear and finished the swingarm on Friday and installed it.
Have to order some stuff for the rear sets. And the foot brake lever is right on top of the header pipe :(
Just bolts on!

Title: Re: Belt tension with longer shocks
Post by Ruttly on 08/28/16 at 10:15:13

I gonna put my carb back together stuff it back in the hole & ride . Then dig out the sportster & ride that too. Feel the need!

Title: Re: Belt tension with longer shocks
Post by Ruttly on 08/28/16 at 22:04:38

Where did you find a drill bit long enough to drill the S/A pivot bolt ?

Title: Re: Belt tension with longer shocks
Post by Armen on 08/29/16 at 02:45:03

"Where did you find a drill bit long enough to drill the S/A pivot bolt ?"

They are commonly called 'aircraft' or 'extension' bits.
McMaster Carr is where I buy my drill bits.
Amazing catalogue. Lots of good info.

Title: Re: Belt tension with longer shocks
Post by justin_o_guy2 on 08/29/16 at 06:06:00

McMaster Carr catalog

What a cool search that turned out to be.

Something I used when I ran a warehouse was
the Thomas Registers

You can look up
Products
Or
Manufacturers
Or
SumthinelseIcantremembernow.

Title: Re: Belt tension with longer shocks
Post by Armen on 08/29/16 at 07:14:15

Justin,
We use their catalogue when designing stuff. If you are wondering which aluminum to use or whatever, you can look it up in that section, decide what kind of stuff you need, and order it. And have it the next day.
Tough to get a catalogue. MSC is the other outfit I use a lot. They'll mail you a truck load of catalogues, but McMaster is a pain. People actually sell the used catalogues on Ebay!
Honestly, it's worth it.
I think the internet killed the Thomas register. We used to have them at our place.

Title: Re: Belt tension with longer shocks
Post by Armen on 08/31/16 at 03:05:54

Talked to the RYCA folks yesterday. The way they do it is basically what I was doing-remove the shock, and set the belt tension at what will be the tightest point in the swingarm travel. This means the belt is pretty floppy at full extension, but they say that isn't a problem.
Looked a Buell yesterday. They use a fixed, large diameter roller under the bottom of the belt. I guess the theory is that as the s/a moves up, belt tension increases, so there is no need for a spring loaded tensioner.
I'll try it as RYCA said. They've certainly built enough bikes with longer shocks, and if they haven't had a problem, it must be OK.
And I'd hate to add a bunch of gak to the nice clean lines of the bike.

Title: Re: Belt tension with longer shocks
Post by Dave on 08/31/16 at 03:42:59

Pretty much the same thing I said.

I have 6,000 trouble free miles since the Cafe' conversion.

Title: Re: Belt tension with longer shocks
Post by batman on 09/01/16 at 11:12:24

I think Dave is right,loose on our bikes can't really do damage ,there are bikes like the yamy 1700 roadstar,bolt R-spec 942 and BMW 800,running 90+hp with no idler pulley on much thinner belts.I don't see why our bikes even with motors built to the max (45hp?) can't handle the load on an even wider belt that is stronger than chain.The belts are built of fibers that that don't stretch ,we can only cause damage by over tightening .

Title: Re: Belt tension with longer shocks
Post by Armen on 09/01/16 at 17:37:40

Batman,
It's not about HP, it's about how much the swingarm angle changes. a 1200 Sportster runs 1/4" of slack. But the s/a lives just about horizontal.
With the longer shocks the s/a droops a lot. As the shock compresses, it comes to almost horizontal, so there is a BIG difference in belt tension.
Ah well, I'm going to run it as is.

Title: Re: Belt tension with longer shocks
Post by batman on 09/01/16 at 21:23:27

Armen , It is about hp! If you snap the throttle closed the sloop in your belt moves to the top side due to the rear wheel moving faster than the drive pulley,now snap the throttle back open and you have belt /chain snatch,a lot more with higher hp,but the savage doesn't have it.