Wing Nut and belt tensioning

[dawz]

we have a 3 B-Type V-belt tensioner for engine with a spring pulling the tensioner roller. The spring is then connected to a stud/hook through the cabin and wing nut is used to pull up the spring to increase the belt tension. 2 wing nuts are used, one on top of console and one at the bottom of console.

Wing nut with spring washer and common washer:

Recently we had a case of loose wing nut and causing damage to thread stud. I have thought of many ways to make it not loose, among them are pvc washers, spring washers, curved washers, Nord locks. I'm sure nord-locks aren't suitable for this application due to belt requiring adjustment after operating for some time. The criteria is not to use spanner to fasten.

the damaged thread:

I had an idea of making a collar to prevent thread contact with metal sheet, but this requires a spanner.

background: Wing nut was used because there was a complain about the v-belt coming loose and operators in the plantation are unable to adjust the belt due to a lack of spanner. So wing nut was selected due to convenience in adjusting belt tension.

I'm sure this invites a lot of criticisms and ideas because, belt tensioning and hand turning doesn't go hand in hand. If you have a better idea, I would love to hear.

For now, belt tensioner was fastened with wing nut, spring washer and common washer with a spanner. But I don't have a convincing enough reason to the team as to why we need to use spanner to fasten the stud other than to prevent loosening/vibration damage to the stud.

 

[TugboatEng]

Think about how long the belts in cars can go without retightening or replacement.

 

[3DDave]

Serpentine belts typically have a belt-tensioning device to continuously control belt tension. I have no good guess for abrasion under the deck of agricultural equipment, but it's got to be faster/more than any typical car will see.

I saw a great instance where the harmonic balancer had a problem and the mechanic took a long time to realize it didn't have a double pulley - the outer pulley had come loose, the belt walked it backwards towards the engine, and the multi-groove belt created a new matching groove profile in the underlying rubber. The tensioner took up the removal of the outer shell. From the amount of rubber dust they thought the belt was going.

Using a bigger/longer spring and eliminating the adjustment is the best way to avoid the whole mess.

 

[TugboatEng]

This applies to your old school V belts as well. Typically one device in the loop would be eccentric mounted which allowed for tensioning of the belt, usually the alternator or poower steering pump. There were no spring loaded tensioners and belts could easily last 50k miles between adjustments.

The key takeaway here is that unless the belts are being used for torque limiting (mower running over a rock) they should last a very long time when properly tensioned. It seems that most people and engineers are unfamiliar with how much tension belts actually need. That's why the serpentine belt setup is great because it has a very stiff tensioner that eliminates people' feelings.

 

[Tmoose]

If the V-belts are loosing tension because they are slipping and wearing in service, Gates used to sell a belt (Green stripe?) for yard equipment that applied and released belt tension as a clutch.
They were/are wrapped with some wear resistant fabric. They don't bend well, so minimum sheave/pulley size is much larger than modern molded cogged/notched VX and plain V series v-belts as mentioned by the honorable T Boat E.

 

[dawz]

Regarding bigger springs, I saw this:

The handbrake lever looks convenient.

I always thought only serpentine belts can achieve that kind of tension and smooth running during operation. In many of the machines I noticed, V-belts tend to vibrate in a blazing fast oscillation.

Agree, no amount of band aid can cure a problem from a bad design.