Selecting a synchronous belt

[Jack Gifford]

I need to select a couple of 8mm pitch belts, 30 mm wide- a 112 tooth and a 134 tooth. The sprockets are traditional tooth profile, not HTD. I can find sources of the belts, but have not been able to find specs- strength, minimum sprocket radius, temperature rating, etc. Most sources don't even state the construction- cord material, etc. Any help would be appreciated. (None of the suppliers responded to my emails).

[jacksoni]

I used Gates GT Carbon  Poly chain belts on my home designed DOHC drive for a custom Infiniti IRL headed GM Iron Duke 4 cyl block. It was only 21mm wide. I don't recall the tooth count. Plenty strong.
  https://www.gates.com/us/en/knowledge-center/resource-library/product-catalogs.html

This link  has the catalog for these with perhaps the data you want. I Also used the Gates iDrive software to design the idlers and such. Was helpful with positioning and lengths to get the tension right.

My engine was run to 10200 for shifts and performed flawlessly even surviving an idler pulley failure that had the belt half shredded and coming off during a run. fortunately it didn't fail completely, was a record run found in Impound and turned out the be the fastest record of the meet that year.

Hope that helps.

[Beltguy]

Jack, I think I can help (34 years at Gates), but we need to clarify a couple of things.  What is application?  Do you have the pulleys?

[Beltguy]

Sorry, keyboard locked up.

The reason I ask about the pulleys is that you say 8mm but not HTD.  There are at least 3 8mm pitch belts and they don't all play well together.

Jim

[johnneilson]

not sure this will help but if the pulleys you have are from an automotive application Gates published a catalog on automotive timing belts.

It was about the most informative when selecting.

Do a little searching, J

[Beltguy]

Jim-
Thanks for responding to my questions. The sprockets are all made from 3" 8mm blower drive pieces, machined to about 1.250" wide, to take 30mm belts. The application is strange. I'm building a two-stage drive for a huge 14-71 blower at 19% of crank speed, utilizing a jackshaft. I don't know specific loads. The second belt needs to drive a billet 14-71 (normal helix, Teflon'd) making about 12-14 PSI (into a 91 c.l. engine) at a maximum speed of about 1,700 RPM. The first belt will be very lightly loaded- about one quarter of the load on the second belt, but up to 9,000 RPM of the 32 tooth crank sprocket.
Thanks, Jack Gifford

Jack, I hope you don't mind that I have posted your message to me here in the forum.  I am doing that to make sure that my response will be available for others to see.

There are two 8mm blower belt profiles.  The first is, indeed HTD and the second is a proprietary profile for the Gates PolyChain belt. It would help me to get my head around this if you could provide the part number for the 3" belt.

It sounds like the blower might be as big as the engine .  If you are saying that you are gearing the drive down to 19% of engine speed, that will have a huge impact on my thought process.

I want to mention the ugly thought of parasitic losses created by the huge rotors of a 14-71 blower.  Even with teflon wipers, it will be significant.

I am running today, so will end this post, I will continue to be active in this thread. 

Jim

[Jack Gifford]

Thanks Jim. I'll get the belt info.

[Jack Gifford]

Jim- Two belts that were run on my sprockets:
Mitsuboshi 1440 H8M
Bestorq 1520-8M

[Beltguy]

Jack, I only had time to briefly look at the Mitsuboshi 1440 H8M belt, but it appears to be a pretty standard HTD (round tooth) profile and not all that special of materials.  I will do some more research in the next day or two.  Trying to get a bunch of stuff done before back surgery in a three weeks.

That part of the timing belt industry is pretty complicated.  There are several 8mm and 14mm tooth profiles by various manufacturers some of which will interchange and some will not.  For our purposes, we can break it down into the HTD (round tooth that has the shape of a "U" and a couple of "gear tooth" looking profiles.  I am pretty sure you have the "U" shaped tooth.  That tooth profile was common in drag racing while the gear shaped profiles were limited (several years ago) to the Gates PolyChain belt.  I suspect I will end up compiling some drawings and downloads into a document I will post here.

BTW, I am starting to read you old inline four thread.  Looks like fun reading.

Jim