Belt reduction - 8M or 14M?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
Alex A.
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Belt reduction - 8M or 14M?

Postby Alex A. » Fri Jan 27, 2017 2:43 am

Good day (or rather night :twisted: ). I am designing an airboat, and I got to a point where I need to select a belt reduction... or rather buy a belt and make pulleys myself (got an acces to cnc machine).

But when I tried to make dealers tell me which type of belt I need it turned out most of them have no clue at all how to properly select them. They just ask for the power and rotation speed, and then type it down into their company's utility program which is supposed to make the selection on it's own. In reality these programs provide invalid or not desirable results, or even no results at all. I even downloaded some of these programs and tried to calculate it myself. It seems that Contitech transmission designer (I have version 7.1) is most serious of them all, so I will use it to demostrate what I try to achive here. And it also seems that it doesn't really matter which brand I will choose in terms of tooth profile - it should be unified.

My dilemma seems pretty simple - should i use 8M or 14M series? I was told both options by different dealers. So here are two things I would like you awesome guys to clarify:

1. Which type of tooth pitch is used on real airboats with power input comparible to mine (see the screenshot below)?
2. Is there someone out here who can tell exactly how to make conclusions out of these calculations (Fu, Fv and Fstat) and why does maximum span tension get multiplied by service factor coefficient (in other words - why is max Fu far more bigger for the industrial lift than for sewing machine)?

Here is a screenshot of Contitech calculator with all of my parameters:
https://i.gyazo.com/e5046a9242e135c0816 ... c9e2f5.png

Gary S
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Re: Belt reduction - 8M or 14M?

Postby Gary S » Fri Jan 27, 2017 7:06 am

Well, there you go.

happy harold
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Re: Belt reduction - 8M or 14M?

Postby happy harold » Fri Jan 27, 2017 7:59 am

you are over thinking your project unless there are no plans to really complete it. pick one and go. my boat has 14 m.

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Deano
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Re: Belt reduction - 8M or 14M?

Postby Deano » Fri Jan 27, 2017 9:07 am

I've gotta agree with Harold, there is no need in re-inventing the wheel
to the extent that your lifespan renders the project to lengthy to complete.

If you look here:
http://www.centurydrives.com/parts_list.htm
You will see that the men who know, are comfortable using 8mm all over the place for up to 600 HP.

Presumably you will want around a 2.3 ratio for your 6000 rpms.
They use a 1256-80-127 HPPD Plus Belt on a CH-3. Which is described here:
http://www.goodyearrubberproducts.com/files/Goodyear/GoodyearPowerTransCatalog/GoodyearPowerTransCatalog1.Page23.pdf

If you need to have the answer to your question, maybe it can be found here: ?
http://www.sitspa.com/1499.pdf

If you want to save time and buy pulleys, rather than make them,
it looks like they might be had here, along with the belt:
http://www.sitspa.com/303.pdf

If you want an airboat and can make stuff, why not just buy one of their belt drives
and then manufacture an adapter plate to fit the engine you are predisposed to using ?

Ultimately, that would leave you more time to enjoy and use it.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

br,lc,LA
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Re: Belt reduction - 8M or 14M?

Postby br,lc,LA » Fri Jan 27, 2017 2:58 pm

Century Drives:
*Briggs belt is good up to about 75hp
*Ecotec Belt is good up to about 250hp
These two drives above are open belt and the lower pulley is cantilever design

CH2 and up well the more hp you make just look at what you need... I kinda agree if you have the tools then buy the belt drive that fits your HP range then CNC your own adapter... These are housing style belts that have the lower pulley between bearings
2016 American Airboat's AirRanger pushed by an Airboat Pros 2015 1.4L GM Ecotec... "Nothin' as Fine as Hearing a Turbo Whine"

Alex A.
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Re: Belt reduction - 8M or 14M?

Postby Alex A. » Tue Jan 31, 2017 8:46 am

Deano wrote:If you need to have the answer to your question, maybe it can be found here: ?
http://www.sitspa.com/1499.pdf
It was a huge help, actually! Not only the calculation guide makes sense, as I was able to determine the pitch and profile i need (8M and HTD), but i also downloaded their catalogue and had a look at it. What I saw there was different types of belts can have up to 2 times (!) difference in power load, so I was asking the wrong question here. :violent1:

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Deano
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Re: Belt reduction - 8M or 14M?

Postby Deano » Tue Jan 31, 2017 9:25 am

That's good news then, glad I could help. :thumbleft:

I would be hesitant to use an 'improved' belt over what Century uses. There may
be other considerations/attributes that aren't readily apparent in catalog specs.
They've been using what they use for over 30 years with nearly 3 times your HP.

One thing is for sure . . . Nobody can accuse you of lacking intestinal fortitude. Image

It seems that in my case with a new build, I can have enough grief
and complications without having to start at that level of scratch. :lol:
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan


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