How to determine proper fan belt size for a bus?

[belfert]

Any ideas how to determine the proper fan belt size for a bus?  I bought new belts since I had everything torn apart.

My Dina parts manual shows 394124665 as the part number.  MCI insists this is not a valid part number.  MCI said to add a dash before the last number and that is a valid number 39412466-5.  The problem is 39412466-5 is shown as the A/C compressor belt for a Dina.  I ordered it since I thought maybe both the compressor and fan belts are the same.

The old and new fan belts appear to be identical in size.  The problem is I cannot get the new fan belts on no matter what even with the idler completey removed.  I ended up unbolting the fan support to get the belts on.  I cannot get the fan support bolted back in without using something like a hydraulic jack to force the bolt holes to line up.  I'm afraid the belt would be so tight as the break the fan clutch or the belt itself.  I even called Bryce to see if he might know how the fan belt should go on since he has worked on Dinas.

The old belts were a size B97 and the new belts only have a MCI part number on them.  The old belts seemed pretty tight so I don't know if they are the correct size either.

What would be the best way to determine to proper size?  I will probably just put the old belts on for now and deal with MCI on Monday.

[Ncbob]

Brian, welcome to the world of bus dilemma! Certainly belts are a very important part of keeping these treasures of ours on the road but, c'mon...let's face it.  You didn't really think that you were going to be able to go to NAPA or the corner auto parts store and buy direct replacements for items like this did you? I know you're more intelligent than that.

And, please don't misunderstand me, I'm in no way trying to demean you and/or your choice of buses. It's just a prominent fact of life that we're going to have problems in logistics with these animals.  Even the outfits like BK's and others tear their respective hair pieces off over replacement parts.

A few years ago a friend of mine from IL, who happened to be in the turf equipment business, was approached by a Japanese Mfr who made quality belts. They made a deal with him to stock everything they made and they'd refer any inquiries on belts to him.  Remember...he was in lawn mowers, etc. He built a secondary business selling belts and matched sets of belts to owners of Rock Crushers, Off Road trucks and whatever you could possibly imagine that would use fan belts.

Therein might lie the tip. You live in a Metropolitan area.  Find the largest distributor of belts and take your problems to him.  You might have to do some homework with a set of calipers before going though.
Measure the width and depth of your pulleys and get familiar with the sizes associated with the pulleys. Then it's just a matter of getting the proper length.  Hope that helps.

Bob

[belfert]

Another note: If I didn't have bad luck I wouldn't have any luck at all.  Besides my fan belt issues, I managed to crack my surge tank where a copper fitting attaches to the aluminum tank.  I was able to get it brazed this afternoon.

I'm going to go out and finish filling the coolant and start the bus as soon as I get off hold with the only truck parts place open Saturday evening.  (22 minutes on hold so far.  I could have driven there already.)  I figure running the engine for a bit with no fan belt won't hurt it a bit.  The fan doesn't come one until 180 or 190 anyhow.

[belfert]

I knew Napa and so on wouldn't have the large belts so that is why I ordered the belts from MCI, but they don't seem to be the right size as they don't fit.  I called Bryce to see if he had any tips for getting the belts back on for a Dina, but he didn't know anything I didn't already try.

I know the belt is a standard B section belt, but I just need to know how to measure properly for a new belt as I've never done this before.  Do I measure to the ousides of the pullies?  I did flip my Yellow Pages open and I see there are five belt places in town.  I just need the measurements and I will go to one of them Monday.

The old belt was a B97 and I might just get a B98 or B99 size as my tensioner has lots of unused capacity.

[Ncbob]

I see your dilemma, Brian. At least you know that it's a 97" B Groove.  That puts you head and shoulders ahead of some.  Again, though, I'd try and find the biggest distributor of Industrial Belts in your area. Now, there are some minor differences between Industrial and Automotive belts...but they could explain and interpolate the difference for your needs.

Bob

[rv_safetyman]

Brian, Gates makes B97, B98, and B99.  A NAPA dealer can order them for you.  You can also go to an industrial distributor such as Motion Industries and get the belt.

"B" section belts are included in a category which is termed "Classical" belts by the industry standard group (Rubber Manufactures Association).  I  served many years on the committee and also served as the US Delegate to ISO for belt standards. 

They can NOT be easily defined by measuring the pulleys or the belts (long story why). 

Your options are to try the B98 or go to an industrial distributor and have them look at pulley combinations with diameters close to yours and look at the center distance for the sizes of belts.  Even that can get you in trouble.  Best bet is to see if you can talk a NAPA store into letting you try the belt for fit with the agreement that you can exchange it.  Be sure not to run it or they will not take it back. 

If your idler is located inside the belt, it may look like you have a lot of movement, but that configuration of idler takes up very little belt.  If the B98 takes up very much of the idler movement, be careful, as wear and stretch will quickly use up the rest of the movement.

We are on the road, but you can call me at 303-478-thirty five 01.

Jim

[mikelutestanski]

hello;      TO give your belt supplier the proper info measure the distance between the pulley centers first..THen measure the OD of the pulleys. Try to get a reasonable measurement for the bottom of the grooves. Record the width of the groove also   Record  on paper or with a small sketch  how the old belt fits into the pulleys. You may want to record the description of the pulleys (ie single groove ,solid center, no holes , no hub etc,etc)     Armed with this info and your old belt  go to your nearest industrial supply house or bearing house and ask for a belt. The guys that do the sizing for industrial  motor pulleys do this all the time.     Now you mentioned a B97 belt. THe older buses with the two stroke Detroits use a C groove belt with the gearbox having a tapered center pulley.  Tapered center pulleys went away many years ago ALL pulleys now are stuck on straight shafts  (A little trivia nothing to do with your problem).  One more item the belt guy will have a set of plastic belt gages which measure the belt and grooves of the pulleys. If you can get a set you can exactly define the groove and with the width, center distance the exact belt can be found..  Keep in mind that belts of this size may not come in inch increments like the smaller belts. You may have to improvise with your fitting technique..   Lots of luck  and FWIW I had to find a new pulley to match the MCI fanbox to to nonexistant Cummins pulley .. ...    Mike   sounds like Jim has better advice and more experience with your setup ....I forgot about the tensioner .  that would change the equation . you should sketch the whole arrangement and take it with you...

[belfert]

Mine is a Series 60 so the belt groove might be different than an 2 stroke.  The belt that was on there is a Dayco BK97.  Dayco no longer has this belt model and doesn't even acknowledge ever making this particular belt model.  I even called Dayco customer service to no avail.  I finally found on the Internet an older Dayco catalog in PDF.  It showed the BK series and the profile is the same as a B groove.  The K stood for Kevlar.

McMaster-Carr, Fastenal, and others all have classical B groove belts, but the belts I have now and the ones from MCI seem to be heavy duty belts.

Bob, I have no idea how to figure out who the biggest belt distributor in town is.  I found out already that some of the belt places in the Yellow Pages only sell conveyer belts.

[rv_safetyman]

Dayco made the kevlar belts for a while to differentiate themselves from others.  The problem with Kevlar is that it is almost impossible to get a matched set of belts because of the very high tensile modulus.  Kevlar is used extensively in the Ag market and does well there, but most of the drives using kevlar are single belt drives.

Any B97/B98 will do a good job, as long as it is a brand name (Gates/Dayco/Goodyear).  Your area will have a Motion Industries.  Also, as I mentioned, NAPA can get them overnight and they will likely be Gates.  Just a bit of trivia, but NAPA and Motion are the same company.

Unfortunately, Mike may be living in the past.  You will probably not get very good "design" service at any belt outlet.  That kind of service is a thing of the past (with very rare exception).  If you try to contact any of the Product Application groups at the belt manufacturers, you will probably be disappointed.  As is the case with most companies, everyone relies on computers and they don't know how to handle out of the ordinary applications unless they have complete engineering detail (blueprints, load/speed data, etc.).  If you can find an "Old Fart" belt engineer that still works in the industry, they can probably find a way to help you, but most of us are doing other things now   That probably sounds like sour grapes and to a degree it is.  I ran our PA group for most of 34 years, and it was sad to see the "decay" of the ability of young engineers to do "Rube Goldberg" engineering.

Now to find a way to get my blood pressure down

Jim

[Stan]

Brian: If the belt you need is in fact a "B" then the width of the pulley grove at the top should be 21/32". To determine the proper belt length for a B belt, measure around the outside circumference of the pulleys and subtract 2".  If the pulley groove does not measure correctly, then the proper belt is not a "B",

[Busted Knuckle]

Brian,
I worked on a '97 Dina yesterday and the NAPA belts it had on the fan were B 98's ! Just thought I'd let you know!   BK 

[belfert]

Brian,
I worked on a '97 Dina yesterday and the NAPA belts it had on the fan were B 98's ! Just thought I'd let you know!   BK 

Interesting.  I'll bet the '97 has a 12.7L motor instead of the 11.1L.  I know the parts book shows a different fan belt for the 11.1L versus the 12.7L.

I wish I would have read this before I ordered another set of B97 belts for spares.  Jim Shepard said I might run out of tensioner if I went to B98.

[Busted Knuckle]

Interesting.  I'll bet the '97 has a 12.7L motor instead of the 11.1L.  I know the parts book shows a different fan belt for the 11.1L versus the 12.7L.

I wish I would have read this before I ordered another set of B97 belts for spares.  Jim Shepard said I might run out of tensioner if I went to B98.

Sorry Brian, I couldn't post it any sooner as I just got the call for an emergency service call yesterday about noon! It was actually a water leak from a couple of pinholes in a hose off the Trans cooler behinde the water pump! Very easy to access from the bottom! By the way I highly reccomend you order a spare replacement for this hose before you need it! It is a molded 90* elbow that is smaller on one end than the other! Luckily the customer had a spare in a box of misc. belts & hoses they kept on the bus! Or they'd been sitting 'til Monday. Or I'd been doing some fancy fabricating, to make something else work if needed bad enough! The info I got of the new hose is; Thermopol #39342237-2 ! If I were you I'd get a spare as it could definetly be a trip stopper!  FWIW   BK 

[Stan]

Brian: If you had to use a jack to be able to bolt in the fan, with the belt on on the pulleys, then the belt is too short. Did you measure the pulleys as  I suggested in a previous post?