Technical Syncros

Why are they usually made of br***?

 

Br*** is a softer metal and it will take the wear when you engage the sychro therefore saving the gear. Cheaper to replace sychro rings than gears.

 

In that particular application, I guess the synchro's br***/bronze (or whatever it is) wears better against the steel (some kind of steel) cones and the steel cones wear better against the br***/bronze. Steel synchros against steel cones might destroy each other? and be very noisy in the process?

 

Br*** is less expensive than 14 karat gold

 

Best combination of wear resistance, friction coefficient and lubrication retention. Same reason its used for bearings.

 

My guess? Probably due to the ease of machining the wear and working surfaces coupled with long life.

The inner female cone surface is carefully shaped to slip and not slip at the right times, lots of little grooves.

Probably hard to do with other metals/alloys. And if steel they would wear into the more expensive parts, main drive gear and other gears.

 

The br*** rings are cone clutches that speed up or slow down the gear selected so that you can shift with no clash. The teeth on the rings prevent the shift until the selected gear is turning the exact speed as the main shaft. I think br*** was chosen for it's wear resistance in this application. You could probably use some type of clutch material, but bonding might be difficult. I think I have seen some plate type syncronizers that do use clutch material. Chrysler used the plate type syncronizer in their early transmissions.

 

Syncro is essentially a friction clutch. If made of steel there would be a high likelihood of galling when engaging the gear. Br*** is a dissimilar metal which makes that unlikely, and presumably has the desired amount of friction to do the job.

 

Late Ford STD TRANS had friction material in the br*** cones and you would use Mercon fluid.

 

I suspect if they were made of steel, the transmission would be welded together after one p*** down the strip.

 

https://balsteelpipe.com/top-materials-for-synchronizer-manufacturing/

"Synchronizer rings are typically made of br***, steel, molybdenum, or carbon fiber, with sintered metals also finding applications. Each material offers unique properties that make it suitable for specific applications:

• Br***: Historically, special br***es like CuZn40A12 have been favored for their good combination of coefficient of friction, wear resistance, and mechanical strength, as described in this patent for a synchro ring manufacturing method. Br*** continues to be a common choice due to its excellent wear resistance and good thermal conductivity, making it suitable for moderate to high-performance applications. Uncoated br*** synchronizer rings with friction threads are a standard, cost-effective solution for p***enger cars, as highlighted by Diehl Group’s brochure on synchronizer rings.
• Steel: Steel synchronizer rings offer superior strength and resistance to deformation, making them ideal for heavy-duty applications, such as in truck transmissions. High-performance transmissions often utilize steel synchronizer rings with various heat treatments and friction layers to enhance performance.
• Molybdenum: Molybdenum is increasingly used in synchronizer rings, particularly in commercial vehicles, due to its excellent wear and friction properties, as explained in Afton Chemical’s resource on how synchronizers work.
• Carbon Fiber: Lightweight and extremely durable, carbon fiber synchronizer rings are the preferred choice in high-performance and racing vehicles where weight reduction and high strength are paramount. It’s worth noting that carbon-based friction materials were initially developed for clutches and brakes, and their application in synchronizers stems from their exceptional durability, as discussed in this SAE technical paper on carbon-based friction materials for synchronizer rings. This highlights the cross-industry application of materials and innovation.
• Copper: Copper, with its lower hardness compared to the synchronizer sleeve material, is used in synchronizer rings to prevent seizure during operation, as detailed in this patent on a synchronizer sleeve. This demonstrates the importance of material selection in preventing mechanical failures.
• Carbon Material: Carbon material is another option for synchronizer rings, offering improved shift feeling and durability compared to traditional br*** rings.

The selection of material depends on factors such as the intended application, desired performance characteristics, and cost considerations."

 

I’d always ***umed that the syncro was used to be sacrificial, and not wear the gears. Good info above

 

You can cut the teeth off the syncho-rings in a lathe and it speeds up the shifting
[we affectionately call it "synchro-smash"]

This is useless for slow smooth shifting unless you develop rev matching skills