Suggestions for Mechanical Linkage Improvement

[ETBISME]

I am currently working on a slow moving (15mph max) off highway vehicle that has a tandem pump directly coupled to the engine. There are two operator control levers connected to the pump via mechanical linkage. Each lever controls the speed and rotational direction of a hydraulic wheel motor.

I am trying to eliminate/reduce vibration transmitted from the pump/engine to the control levers, while limiting the amount of "dead" or “lost” motion while actuating the levers. Here are some of the suggestions or prototypes I have recommended to the customer.

1) vibration dampening rod ends
- did not effectively dampen vibration,
introduced excessive “lost” motion
2) “steer-by-wire” servo-motor actuation
- too expensive
- customer prefers simpler solution
3) push-pull cables
- eliminated vibration effectively,
high quality cable had minimal lost motion
- customer has previously had “bad” experience,
says $15 per cable is too high for production
4) dual bell crank mechanical linkage
- reduced vibration, lower cost than cables,
- complicated assembly, excessive lost motion

OK, can anyone come up with any other solutions? I prefer the push-pull cables if I can prove their merit to the customer. Any info or ideas will be appreciated!

 

[TStaples]

ETBISME,

I do not know if the current linkage setup is steel rods, or stamped parts, or what have you. If the design consists of stamped or tubular pieces, you should consider using laminated steel. A major US pickup truck manufacturer has run commercials touting "quiet steel." Same stuff. I have seen this used in an off-highway application to reduce vibration transmitted into a component mounting box with tremendous success.

Along that same thought path, golf club shaft makers have had vibration dampening steel shafts for many years. They either coat the I.D. of the tubular shaft with an elastomer, or install tightly fitted plastic inserts into the I.D.'s..





-Tony Staples

http://www.tscombustion.com

 

[Fabrico]

I too would push for cable control. The $15 concern could be valid but cable control is incredibly popular for that very application, and not particularly because of costs.

 

[IceStationZebra]

Cables have the benefit of easier control layout. You don't need direct line of sight. You might also have the potential for more subassembly off of the main line. You can get good push/pull cables for the off-road industry, you just get what you pay for.

As to your original question if possible I would look at some of the big name skid steer makers for inspiration. There have been numerous ideas tried throughout the years so the latest designs should be fairly mature.

You also didn't describe the vibration in much detail. One source would be vibration in the chassis going through the cab and control lever. I don't think this is your concern but it could be adding to the problem depending on the operator platform/cab isolation or lack there of. I assume your main problem is vibration coming through the linkage from the motors. One idea that I haven't seen before is a tuned spring/mass damper on the linkage. It would need to be a set of tuned weights and springs sliding on the linkage axis.

I also realized that one version you didn't mention was hydraulic pilot control. It is very robust and should be cheaper than drive-by-wire but probably more than cables. It is also easy for service people to deal with - easier to understand than "smoke in the wires." Depending on the size of your pumps you could probably directly control the servo cylinders in the pumps.

Another idea would be to have vibration dampened lever pivots.

And of course there is the old stand-by - large "spongy" control grips.

ISZ

 

[thundair]

I always favor bell cranks and just finished a design where a bell crank system expanded a 4 segment pie section to increase the diameter with ....no lost motion..

I often wonder but haven't tried it yet if you could dampen vibration with magnets pulling (but not in contact) in a canceling direction...

Cheers

I don't know anything but the people that do.