Author Topic: belts for 2 3/4  (Read 9667 times)

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Offline gsx1100s

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belts for 2 3/4
« on: 05 Jun 2007 at 23:48 »
Does anyone know where to get belts for the 2 3/4 ? I am not fussed if it is the daisy chain or single link.
Thanks in advance.

cheers Michael
"My first car was a motorcycle"

Offline Alan Cun

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Re: belts for 2 3/4
« Reply #1 on: 06 Jun 2007 at 09:03 »
  Hello Michael   Check out our discussions on belt slip and hub lube elsewhere on forum. I guess the best place to look for a belt is the yellow pages particularly Engineering supplies  Belts and Pulleys etc Might have to look a little way out of town to farming suppliers.   As for section belts dont waste your money, my opinion only.  Dunlop General Products in Brisbane were my supplier but I think that was their Aust base.    Regards Al

Offline graeme

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Re: belts for 2 3/4
« Reply #2 on: 06 Jun 2007 at 13:43 »
Try an SKF bearing shop. They stock Opti belts, which come in 1" increments. Not expensive at all -the one I got for the 3 1/2HP was under $40.
Ian - have you worked out the size belt to suit a 2 3/4?

Graeme

Offline Chris

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Re: belts for 2 3/4
« Reply #3 on: 06 Jun 2007 at 17:52 »
I believe the correct original belt size for 2.3/4hp machines was 3/4". This size does not seem to have been made for many years. Optimat belt comes in two sizes for motorcycle use 17mm suitable for small veterans (it will work on the Douglas but rides a bit low in the pulleys) and 22mm which is a bit large and rides high in the pulleys (it is this size that is most commonly used). This belt, if genuine Optimat, seems to have quite a good life and does not stretch too much after initial fitting. It is joined by their own Optimat clip comprising two plates and two screws that go through the holes that are spaced at about 1cm distance along the whole length of belt. There are cheap and nasty versions of belt of identical appearance that stretch very badly and is soon affected by oil. The genuine Optimat in England is not cheap and is certainly very much more than the price quoted by Graeme. Chris.  

Offline Ian

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Re: belts for 2 3/4
« Reply #4 on: 06 Jun 2007 at 21:58 »
I have been playing round with belts. Seems to me normal C section is fine on the TS. I have been running one of the modern segmented belts but have just changed over to a rubber V belt. A C80 was too long and a C78 too short where I have my gearbox set - Alan C suggests adding a half link to the primary to make it fit. A C79 would probably be OK for me. However I decided to use the old joining link I have run on the 7/8 section belt I used to have on it - will be trying it out at the Debenham rally in a weeks time ...Ian

Offline graeme

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Re: belts for 2 3/4
« Reply #5 on: 07 Jun 2007 at 02:05 »
The link will pull out of the belt - gauranteed! We've been down that path in the past. Continuous belts have only radially laid fibres - nothing for the link pins to grip onto. If you haven't already cut the belt Ian, don't. You can throw it away if you have.
The Opti belt that I am talking about is a continuous belt - not one made to be joined with a link. From our experience they do not stretch at all.

Graeme

Offline Ian

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Re: belts for 2 3/4
« Reply #6 on: 07 Jun 2007 at 02:30 »
Graeme, I have certainly heard that re modern V belts - was just interested to see if a motor with the incredible power of the TS would pull it apart. I am going to take the other belt with me so if it does go i will swap over. Am going to go long term with a C79 when I can find one as it should be about perfect.
Interesting thing though - I had always thought the number in the definition of the belt was a direct reference to the inches. However I now can see why it is hard to measure - below are the ISO definitions of the belt sizes. The first big number is the "nominal measure" and the second is the "inside measure". As you can see from a C78 to C79 we have 19mm and a C79 to C80 is 32mm !! No wonder the C80 I got was so much bigger.

C 78 2039 1981
C 79 2058 2000
C 80 2090 2032
C 81 2118 2060
« Last Edit: 07 Jun 2007 at 02:52 by Ian »

Offline gsx1100s

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Re: belts for 2 3/4
« Reply #7 on: 07 Jun 2007 at 02:55 »
Thanks for the great feedback , further to the original question , what length of belt is required? is it "cut to length" or is it particular to the model of Douglas?

cheers Michael
"My first car was a motorcycle"

Offline Ian

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Re: belts for 2 3/4
« Reply #8 on: 07 Jun 2007 at 03:08 »
Michael, for the continuous belts they are just manufactured in defined sizes. Depending on the length of your primary chain and thus the position of the gearbox a C78 or C79 would work. On mine the C78 was far too tight. Alan C said that a C78 works with a half link in the primary. I am trying the other route of the slightly longer (19mm) C79 belt.

Offline gsx1100s

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Re: belts for 2 3/4
« Reply #9 on: 07 Jun 2007 at 06:27 »
Michael, for the continuous belts they are just manufactured in defined sizes. Depending on the length of your primary chain and thus the position of the gearbox a C78 or C79 would work. On mine the C78 was far too tight. Alan C said that a C78 works with a half link in the primary. I am trying the other route of the slightly longer (19mm) C79 belt.

Thats quite interesting , so there is a constant trade of between the tension on the primary Vs the tension of the belt. Would this mean that as the primary chain stretches , one must invest in a new belt or re adjust the rear wheel ? or is the wear so little and the stretch so minor that the belt is realy no issue?


P.S. Thanks for letting me constantly harrass you all  :wink: ,

cheers Michael
"My first car was a motorcycle"

Offline Ian

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Re: belts for 2 3/4
« Reply #10 on: 07 Jun 2007 at 06:34 »
Yes - the gearbox can be moved to adjust tension on either one. Once set it should be OK for ages.

Offline McKaige

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Re: belts for 2 3/4
« Reply #11 on: 29 Jul 2012 at 10:39 »
Ian, I have just read your note on belts for 2  3/4. I live in Melbourne. Who supplies belting?
I bought a length of green perforated V belt but that was 30 years ago!
Chester

Offline Ian

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Re: belts for 2 3/4
« Reply #12 on: 30 Jul 2012 at 11:12 »
Chester, for the normal C section belts most bearing/transmission places sell them (CBC, etc)

I did buy some belt from a guy in Victoria a few years back which has the line of holes which you can attach the belt joiners to - I can't find who it was - I want to buy some more !! Its really good. I will try to find my records on it ...Ian

 

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