bgm Pro Silk Liner

The beauty of the classic gearshift controllers is the very simple technology. Whether it's the engine, the electrical system or the controls. Everything is kept very simple and efficient. But even the simplest components have changed a lot in recent decades. Whereas the first Vespa models still used simple, bare steel bowden cables that had to be constantly maintained with grease and oil, modern cables are now fitted with a so-called liner. The liner is a small tube made of a very slippery material that is located in the outer casing and makes constant maintenance of the cables practically superfluous. This effect has already been explained in a blog.
The new liner of the bgm Pro Silk Liner cables offers very low resistance for the inner cable, even under high loads, and therefore extremely low operating forces. The crux of the matter with old, worn or poor cable pulls is that the more force is required to move a component via the cable pull, the greater the force required to overcome the resulting friction of the pull alone. As a small theoretical example, consider the operation of a clutch with an old cable pull. Actuating the clutch requires a pulling force of 10 kg directly at the clutch arm on the clutch cover. However, if you pull the cable at the top of the handlebars to actuate this clutch arm, the force required here is significantly greater than on the clutch arm directly.

Why?

On its way up into the handlebars, the cable has to describe a few radii, so it has to go around the curves in the frame and steering head. These radii are the points at which the inner cable rubs more strongly in the outer casing. This friction is increased by the sum of the radii on the way up to the lever. This means that at the top of the lever, 12kg instead of 10kg of pulling force is required to overcome the friction of the cable. Now we equip the clutch from our example with stronger springs. This means that a tractive force of 15 kg is required directly at the bottom of the clutch arm to actuate the clutch. However, the tractive force required at the top of the lever is now 25kg instead of 17kg. This is because the friction within the cable pull increases drastically many times over due to the higher load on the clutch arm. This is where modern materials intervene to reduce this friction at high loads. I have carried out a small test for you to find out how much force is consumed by which type of cable pull. To ensure that the test produces a meaningful result, all the cables tested are always the same length and are intended for the same application on the vehicle. In order to test the effect of the increased friction in the difference, I have greatly increased this range. This means that each cable was always laid with 2.5 windings around a round body. This creates many more radii, i.e. friction points, than is possible in a vehicle. This exaggeration only serves to make the results clearer.

Here is the "test setup".

The cable is guided and fixed around a pulley with two and a half strokes. To simulate that the train actuates a clutch, I hang an appropriate counterweight on one side of the train and a tension scale on the other side of the train to obtain the value of the required tractive force.


In this case, my counterweight is a small collection of crankshafts that together weigh 10.9 kg.


My first example is a normal, new standard cable, as found in almost every old Vespa. This cable does not have an inner liner to reduce friction, instead the cable runs directly on the steel windings of the outer casing (Bowde) and is only lubricated with grease.

This requires over 70 kg to overcome the breakaway torque of the cable and to move the small package of crankshafts evenly with only 10 kg on the other side. The second attempt is made with a performance cable from another supplier. This cable has a liner and ground inner cables to reduce friction.

In this test, the 10.9 kg crankshafts can be moved with just over 27 kg of pulling force. In the third test, I put the bgm Silkliner around the pulley with two and a half strokes.

The Silk Liner was able to beat the good result of the Performance cable once again. Thanks to the very slippery liner inside, the weighty package of crankshafts can be lifted with just 23.5 kg of pulling force. Transferred to the lever ratios on the vehicle, this further, considerable reduction in the necessary pulling force helps to ensure a high level of operating comfort and a pleasant driving experience. With the bgm Pro Silk Liner we have paid attention to many other details in addition to ensuring the lowest possible operating forces. Over the years and many thousands of scooter kilometers, we have put the experience we have gained into the composition and production of the bgm Pro Silk Liner trains and train sets. We are proud that we can now offer you the bgm Pro Silk Liners

The bgm Pro Silk liner train sets are available for the following vehicles:

• We offer the bgm Pro Silk liner train sets for the following vehicles:
• BGM6460SL Train set -BGM PRO, Silk Liner- Vespa V50, V90, PV125, ET3
• BGM6470SL Train set -BGM PRO, Silk Liner- Vespa Rally180 (VSD1T), Rally200 (VSE1T), Sprint150 (VLB1T), GT125 (VNL2T), GTR (VNL2T), TS125 (VNL3T), GL150 (VLA1T)
• BGM6412SL Train set -BGM PRO, Silk Liner- Vespa PX Lusso (1984-) - black
• BGM6410SL Pull set -BGM PRO, Silk Liner- Vespa PX Lusso (1984-

• BGM6422SL Pull set -BGM PRO, Silk Liner- Vespa PX old (-1984) - black
• BGM6420SL Train set -BGM PRO, Silk Liner- Vespa PX old (-1984)
• BGM6430SL Cable set -BGM PRO, Silk Liner- Vespa PK XL2 - without shift cable
• BGM6440SL Cable set -BGM PRO, Silk Liner- Vespa PK XL1
• BGM6450SL Cable set -BGM PRO, Silk Liner- Vespa PK S
• BGM6465SLB Pull kit -BGM PRO, Silk Liner- Piaggio Bravo

bgm PRO Silk Liner