Below is from Darrell Voss who worked with Gary Klein on development of the Mantra:
When we were building the preproduction units, the shock options were not working well for us. We just could not get the performance where we needed it. We had worked with Fox and Rock Shox engineers but nothing was coming from the interaction to support our efforts.
Internal break through:
After a bit of struggling, we stumbled on putting a joust bumper on the shaft of the rear shock and did some fine tuning of the damper. This became the first production lots. It was still not perfect, and fell short of our goals, but it was still an improvement from what was out in the market at the time. You can look back at some of the early releases of the Mantra (first year of production) with the Fox shock on it and see that there was a joust (MCU spring) bumper added to the shaft. This added in creating a nice mid and end of stroke spring compression rates.
Not sure if you took the one apart you have but in the bottom there is a damper that uses silicon oil (the oil is compressible). The design of the damper used a fluid logic valve with no moving parts. It changes the resistance based on the impact and speed to the vehicle structure. The compressibility of the fluid reduces the initial spike on larger impacts while still providing overall control.
We were seeking the best way to enclose the MCU springs and damper unit. Realizing the cosmetic looks were not as nice looking, compared to most of our work, we where continually seeking a solution to the shock unit. We were under pressure to unveil our suspension efforts to the public. What you have is one of three preproduction units. The other two are owned by myself and Gary and are the larger size (22”). Yours is a medium (20”).
In order to create
adequate spring forces, with an MCU, we built two
chambers which are stacked on top of one another. In
order to keep the structure weight down, we only added
material to the outside where the clip rings where
positioned on the inside of the chamber for the MCU. The
Rock Shox lines of suspension fork lowers have a similar
design now (15 years later) with their power bulge in
the bushing area.
Click on thumbnails below for larger images:
|Fork||Rock Shox Judy SL|
|Hubs||Shimano Deore XT|
|Crank||Shimano Deore XT Hyperdrive C|
|Rear Cogs||Shimano 8 speed cassette|
|Bottom Bracket||Shimano sealed cartridge|
|Rear Derailleur||Shimano Deore XT|
|Shifters||Shimano Rapid Fire Plus 8 speed pods|
|Handlebars||Klein Mission Control|
|Stem||Klein Mission Control|
|Brake set||Shimano Deore XT V brakes|
|Brake levers||Shimano Deore XT V|
|Saddle||SDG Bel Air|
More MOMBAT-themed resources.