V-Belt Systems on our Eagle Buses

[beltguy]

Wayne Schell and I have had several phone conversations about the alternator belt drive on the Cummins engine in his 05. The bus was not charging properly and it appears that the problem was that the belt was bottoming out in the driver pulley. As we talked, it became clear that I should probably discuss all the variations of V-Belt drives that we might encounter on our buses. This based on 34 years of experience at The Gates Rubber Co

I will focus on the 05 and 10 models, but I think most of what follows pertains to most models.

Let's start out talking about what possible belt cross sections we might encounter on both a stock Eagle and one with an engine conversion. I make the distinction because our two stroke engines have gear driven accessories except for the alternator which is driven off the bearing housing at the end of the miter drive. There could be 4 different cross section categories that might occur on our buses: two automotive series standardized by SAE and two are industrial series standardized by RMA (Rubber Manufacture's Association. Both also have ISO equivalent standards.

I will start with the automotive sections. The following photos list two different series of automotive belts. At Gates we called them the "fractional" and "high capacity". You can see that the first few cross sections are described in decimals and those are the "high capacity" sections. Those are followed by the "fractional" sections.

The "fractional" automotive sizes have been around forever. If you have an old car/truck/tractor, you have seen the very wide belts that were used in the 40's and 50's. In the early 50's the car manufacturers started converting to the narrower "high capacity" (HC38 and HC50) sections. The heavy duty automotive (bus/truck/etc.) market was much slower to adopt the "high capacity" belts.

I will continue this discussion in subsequent posts.

Jim

[beltguy]

In the first post we detailed the Automotive (SAE) section belts that might be used on our buses. In this post I will describe the industrial (RMA) sections that you might see on either a stock or modified Eagle.

In the attached Dodge sheave groove table you will see two categories: Narrow and Classical. As was the case with automotive belts, the Classical belt sections ("A", "B", "C", etc.) have been around for many decades. The Narrow belts (3V, 5V, 8V) were developed in the 60s.

For the "car" industry, industrial belts were never applied to engine applications. However, when it came to the truck/bus/agricultrual/construction equipment, the manufacturers sometimes used both Automotive and Industrial belts. That really makes it hard to try to determine what replacement belt should be used. Then, some of us cobble up drives that mix automotive and industrial belts and sheaves.

The reason I have attached documents that show the belt and sheave information is to help you sort out what kind of belt/sheave drive system you are dealing with.

More to follow.

[beltguy]

Now that we have described the various series of belts that could be used on our buses, I need to emphasize that trying to apply one series of belts to a different series of sheaves can cause problems - you should not mix and match systems without careful consideration.

I will use Wayne's drive as an example. Based on our conversations, it appears that his Cummins had either 11/16 or 3/4 grooves for the alternator. We did not finish laying out all the details, but it appears that someone applied industrial 5V belts to that groove. It worked fine for many years. However the 5V belt is significantly thicker that the 11/16 or 3/4 inch automotive belt and as they wore down, they bottomed in the driver sheave groove and would not transmit the power needed by the alternator to charge the battery. Wayne had the alternator checked and it was working properly. My recommendation was that he go back to the alternator rebuilder and get a "fractional" automotive groove pulley and then get a "fractional" belt to match the grooves.

I just talked to Wayne and his belts should be in today. I will update the results of this effort after we get the final details.

Jim

[beltguy]

One last post for a while and then I will stuff a sock in it

As I mentioned earlier, most of the accessories on a two stroke are gear driven. The three major belt drives on a stock Eagle are: alternator, factory AC, and fan. It appears that the stock alternator drive (off the bearing housing driven by the miter box) is driven by three 3V industrial belts. I have attached a photo of that drive and of the Eagle parts listing from a 1991 Gates Catalog.

The fan drive comes off the same bearing housing and uses two belts to drive the fan. As you can see for my old Gates catalog, the belts for the fan are listed as 449 which is/was an automotive 11/16 belt 89 1/4 inches long. That belt has long been discontinued and most folks use a set of "B" section industrial belts and they work just fine.

I really don't recall much about the AC compressor drive. Most of us remove that hardware. For reference purposes, the belt that Gates lists for that drive are 452 which is an 11/16 by 86 5/8.

Gates has discontinued many of the old "fractional" automotive belts. I have not checked recently, but I think Dayco still has a significant list of these belts.

Jim

[beltguy]

I thought I would bring this thread to the top again, since there have been a couple of threads about the fan drive belts.

Jim