# Sizing a fan belt



## User Friendly (Nov 25, 2021)

Hi there 
I was looking for guidance on a replacement fan belt for my Iseki 150

















It's quite slack and the alternator is at max adjustment, which may be the reason the battery has failed to charge ona couple of occasions 

The manual says 939 (36.97) HM type, but none of the local guys seem to know what that means, and as you may know, I be a n00b

If someone could teach me to interpret what the numbers on the pictured belt mean, and how to select the best size, I'd really appreciate it

Thanks


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## Bob Driver (Nov 1, 2017)

Plug your belt #'s into the link below to get x-references. If those belt #'s don't come up, use the "length" box and plug in 37"
Belt X-reference link

To determine if 939MM - 36.97" (37") is actually the correct belt length you need, use "Method # 3" in the belt calculator link below to calculate the actual length needed. Measure your pulley "center distance" (see Method #3 in the calculator link) with the alternator set a mid-travel on the alternator adjustment mechanism
Belt Length Calculator


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## Groo (Jan 17, 2020)

If I search for an XPZ 0950, that shows up as a 950mm belt, so a bit too long.


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## Bob Driver (Nov 1, 2017)

Usually 7/16" (11MM) wouldn't be that much of an issue, but the belt may be stretched a bit, and the pulley grooves could be worn also.....


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## Groo (Jan 17, 2020)

Bob Driver said:


> Usually 7/16" (11MM) wouldn't be that much of an issue, but the belt may be stretched a bit, and the pulley grooves could be worn also.....


Looks like a HM belt is a fair bit larger than a XPZ belt in cross section. 50mm wide vs. 10mm. That will make much more difference than the 11mm of length difference.
The HM belt looks to be a variable speed belt, like used on a snowmobile, golf cart, and now ATVs and UTVs

The HM cross section looks the be used with combines, so I suspect that isn't what you are looking for.

I do see reference to Kubotas using belts numbered like HM37, which is their HM section x 37"
That is probably what you really want. AIRCAP HM37 Replacement Belt - Off Road Belts LLC


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## bmaverick (Feb 20, 2014)

User Friendly said:


> Hi there
> I was looking for guidance on a replacement fan belt for my Iseki 150
> View attachment 76983
> 
> ...


939mm length from the manual. You are holding a 950mm in the pix. That's a mere 11mm more in the pix and would explain why the alternator is at it's max bracket positioning.  

11mm = 0.433 inch. (11 / 25.4) aka 7/16ths 

939mm / 25.4 = 36.96 inches. 

Like Groo mentioned, it's more than length. Those pulley groove sizes will also dictate the final width. If you can't find a belt with the proper width, a close width and some tweaking in length is required. 

At the bottom of this link is a video that will help tuning in to a belt or belts that would work. 





V-Belt Global Supply, LLC. | V-Belt Online Catalog


Shop VBeltSupply.com for power drive belts! We are the largest online distributor of v-belts, including industrial, Kevlar, timing, cogged, and more.




www.vbeltsupply.com


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## User Friendly (Nov 25, 2021)

I guess I'll tie some string around the mechanism and measures it


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## Groo (Jan 17, 2020)

User Friendly said:


> I guess I'll tie some string around the mechanism and measures it


a V belt is never suposed to bottom out in the groves put the string at the top of the grooves.


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## User Friendly (Nov 25, 2021)

Groo said:


> a V belt is never suposed to bottom out in the groves put the string at the top of the grooves.


Top tip, thanks


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## Bob Driver (Nov 1, 2017)

Groo said:


> If I search for an XPZ 0950, that shows up as a 950mm belt, so a bit too long.


Yep.... the 0950 is a dead give away to 950MM. Also noticed one of belts is a cog belt.


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## Bob Driver (Nov 1, 2017)

User Friendly said:


> Top tip, thanks



A string gives you the outside dimension of the belt. Some belt part #'s are listed using the outside dimension, some belt part #'s are listed using the inside dimension. Be sure you know the belt # you order is outside dimension if you use just a plain old string....


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## User Friendly (Nov 25, 2021)

Bob Driver said:


> A string gives you the outside dimension of the belt. Some belt part #'s are listed using the outside dimension, some belt part #'s are listed using the inside dimension. Be sure you know the belt # you order is outside dimension if you use just a plain old string....


Considering the amount of adjustment in the alternator position, surely the belt size is not that critical?


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## Bob Driver (Nov 1, 2017)

User Friendly said:


> Considering the amount of adjustment in the alternator position, surely the belt size is not that critical?


That's the point I was making in the 4th post of this thread.......


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## User Friendly (Nov 25, 2021)

Bob Driver said:


> That's the point I was making in the 4th post of this thread.......


What would you say my margin of error is?


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## User Friendly (Nov 25, 2021)

So I did the string thing 

The relatively large adjustment only translates to a 15mm in belt size, so the 939mm from the manual is right 

Just need to find one now!


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## Groo (Jan 17, 2020)

what is the width of the groove at the top of the pulleys.


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## User Friendly (Nov 25, 2021)

Groo said:


> what is the width of the groove at the top of the pulleys.


10mm


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## Groo (Jan 17, 2020)

I think the kubota hm belts were 15mm, so not that either. Might as well stick with another XPZ950. Lots of them for sale on-line.


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## User Friendly (Nov 25, 2021)

Groo said:


> I think the kubota hm belts were 15mm, so not that either. Might as well stick with another XPZ950. Lots of them for sale on-line.


The 950 is to big, unfortunately 
I'm going to go to the Irish Iseki dealership see if they have a 939


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## Groo (Jan 17, 2020)

Too long or too worn? 
There is an XPZ937 as a standard size.


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## User Friendly (Nov 25, 2021)

Groo said:


> Too long or too worn?
> There is an XPZ937 as a standard size.


Good question 

On 6 months done maybe 20 or 30 hrs 

Doesn't look worn or damaged 

Can you recommend a seller 

It's been surprisingly difficult finding what I want 

I found a 940, but when it arrived it said 950 (36.5") and looked _longer _than the old one


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## bmaverick (Feb 20, 2014)

User Friendly said:


> 10mm


Close is A35 or A36. Length is A35 = 37-inches on outside and A36 = 38 inches outside. 

1/2 inch = 12.7mm 










Gates and others make a 3V Wedge Belt. This on sits at a really nice size. 3/8 = 9.5mm It's super close to the width you need. These are used in automotive and are very durable. 
3V Belt Type X 3/8 Inch Top Width X 37.5 Inch Outside Diameter | Wedge Belt (vbeltsupply.com) 









A tad longer
3V Belt Type X 3/8 Inch Top Width X 38 Inch Outside Diameter | Wedge Belt (vbeltsupply.com) 

A tad under sized
3V Belt Type X 3/8 Inch Top Width X 35 Inch Outside Diameter | Wedge Belt (vbeltsupply.com)


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## bmaverick (Feb 20, 2014)

Groo said:


> Too long or too worn?
> There is an XPZ937 as a standard size.


Yes, that a Gates p/n too.

Gates XPZ937 Metric V-Belts - $5.29 (vbeltsupply.com) 

Knowing that 1mm = about the width of a pencil lead before the point, 939mm vs. 937mm is just two pencil widths in difference. Almost nothing to write home about. hahahaha Seriously, for the price above, I would take the stab and order it and give it a try. Gates is a durable brand, and in the racing circles, it's a primary go to belt brand.


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## Bob Driver (Nov 1, 2017)

Man, this has got to be a record, 24 post/6 days about simple v-belt part #. Just pick a lane as far as the outside length you want and slap a FHP belt on, it's not the space shuttle....... It's a fan belt
10mm = 3/8" (3L FHP belt x *outside dimension*)

3L355 -- 3/8 x 35.5" (outside)
3L360 --- 3/8 x 36" (outside)
3L365 --- 3/8 x 36.5" (outside)
3L370 --- 3/8 x 37" (outside)
(See the # pattern?)

Gates, Dayco, Goodyear all use these universal #'s for FHP belts and make these sizes of belts. Your local belt guy may not carry it in inventory, but they can damn sure order it..... Belt will cost $8 tops and you'll have your machine back running before St. Patrick's Day.


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## Groo (Jan 17, 2020)

Bob Driver said:


> Man, this has got to be a record, 24 post/6 days about simple v-belt part #. Just pick a lane as far as the outside length you want and slap a FHP belt on, it's not the space shuttle....... It's a fan belt
> 10mm = 3/8" (3L FHP belt x *outside dimension*)
> 
> 3L355 -- 3/8 x 35.5" (outside)
> ...


FHP stands for Fractional Horse Power, as in intended to transmit less than 1 horsepower. Just no. Dad's sawmill came with a FHP belt for the hydraulic Pump. I was constantly changing them until I realized what FHP stood for. An equivalent lawn belt lasted at least 5 times as long.


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## Bob Driver (Nov 1, 2017)

Groo said:


> FHP stands for Fractional Horse Power, as in intended to transmit less than 1 horsepower. Just no. Dad's sawmill came with a FHP belt for the hydraulic Pump. I was constantly changing them until I realized what FHP stood for. An equivalent lawn belt lasted at least 5 times as long.


That's it Bud..... Just keep the breeze blowing. I wonder the difference in torque required to drive a hydraulic pump on a sawmill and a cooling fan on an AG tractor? Add a "K" on the end of the belt # and get it in Kevlar. Buy two and keep one as a back up, they're only $8.... Geez talk about over thinking a fan belt. I'll just sit back and enjoy the continuing OCD debate now..... 26 post and counting over a simple fan belt, this is fun to follow


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## Groo (Jan 17, 2020)

Bob Driver said:


> That's it Bud..... Just keep the breeze blowing. I wonder the difference in torque required to drive a hydraulic pump on a sawmill and a cooling fan on an AG tractor? Add a "K" on the end of the belt # and get it in Kevlar. Buy two and keep one as a back up, they're only $8.... Geez talk about over thinking a fan belt. I'll just sit back and enjoy the continuing OCD debate now..... 26 post and counting over a simple fan belt, this is fun to follow


it is a worthy discussion. It may be less than $20, but sometimes they are a real pain to change, and a failure can really strand you in a bad way.

As to the power requirement, the XPZ looks significantly stronger than a FHP, and the XPZ looks plenty worn.

ps. I would be surprised if the belt on my crawler is has been changed in my lifetime.


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## bmaverick (Feb 20, 2014)

Oh the sufferings of having the RIGHT belt and RIGHT length on equipment that constantly fails. I've been there with a JD261 finish mower. Frustrating to no end when the belt kept breaking and there were no Kevlar equals to the part number. BUT, after sleuthing around I found a Bxx match and it came in Kevlar. Seldom from that point on did the mower eat a belt! 

Thus, I can really understand WHY this thread is exhaustively long with posts.  

Lots of options here. I'll pick the same one Groo selected too as the first one to go after. Have it at your place in under 5-days. Less than $10 with shipping! I get all my belts from Vbeltsupply. 

*GATES XPZ937
Gates XPZ937 Metric V-Belts - $5.29 (vbeltsupply.com) *

V-Belt Global Supply, LLC. is an Internet based full service company based in Sioux Falls, SD. We began operations in Feb. 2009. Our core business is partnering with purchasing and maintenance departments, engineers, as well as with supply companies to provide belting solutions and education for your projects and your customers. Our partnerships include: End Users, OEM's, Manufacturers, Aggregates, Municipalities, Recyclers, Oil Services Companies, Agriculture Retailers, Lawn & Garden, HVAC, Exporters, and many other industries. With over 8,000 business clients, including Monsanto, University of Texas, Department of Homeland Security, Motion Industries, Grainger, General Mills, Alcoa, Caterpillar, and British Petroleum; our belt teams can find solutions for any company, big or small.


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## Bob Driver (Nov 1, 2017)

It's still just a fan belt......😁


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## User Friendly (Nov 25, 2021)

Apologies for noobing you out Bob Driver 

I'm a delicate flower 

I'm going to get this 

*XPZ 937 mm Lw = 9,5 x 950 mm La = AVX 10 x 950 mm La*

but all the numbers and letters are spooking me 

The eBay page is in German also which is not helping


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## Bob Driver (Nov 1, 2017)

User Friendly said:


> Apologies for noobing you out Bob Driver
> 
> I'm a delicate flower
> 
> ...


OK..... Only took 30 post and 15 days to figure out a $5 fan belt. Sorry you got buried in a "BS Blizzard", hope it works out for you.


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