Thursday, May 30, 2013

SPQ 13 Daniel

Hydraulic Cycle Times

Here is a video of the Bobcat Excavator's bucket curling both ways. The machine is at operating temperature, about 150 degrees. Also the engine is at high idle.

Here are the cycle times.

Bucket Dump: 1.25 sec               (manual spec: 1.9 sec)
Bucket Curl: 2.3 sec                    (manual spec: 2.7 sec)

Next is the travel speed. Again the machine is at operating temperature and the engine is at high idle. This Bobcat has two speeds; a low gear and a high gear. This next video will show how many revolutions the track will move in one minute. There is a piece of red tape on the track to show when one full revolution is completed. Also the length of the track is 173 inches.

Revolutions in 1st gear: 11rpm

This next video is the Bobcat is in 2nd gear.

Revolutions in 2sd gear: 18.25rpm

So here I did some math to take the RPM and turn it into MPH. Hopefully I did the math right.
1st gear

11rpm x 173" = 1903 in/min
1903in/min / 12" = 158.583ft/min
158.583ft/min x 60min = 9514.98ft/hr
9514.98ft/hr / 5280' = 1.8mph

2nd gear

18.25rpm x 173" = 3157.25in/min
3157.25in/min / 12" = 263.104ft/min
263.104ft/min x 60min = 15786.24ft/hr
15786.24ft/hr / 5280' = 2.99mph

The outcome speed of the tract:

1st gear: 1.8mph              (manual spec: 1.6mph)
2nd gear: 2.99mph          (manual spec: 2.9mph)

Here is the procedures for when a new hydraulic pump is installed in a machine. This will prevent a dry start up of the hydraulic pump.

·         Loosen the case plug until all the air is purged from the pump housing.

·         You will need to crank the engine without starting it. To do so use a bypass tool that can be hooked to the starter solenoid battery terminal and S terminal.

·         Crank the engine for 15 seconds, then stop for at least 30 seconds. Again, crank the engine for 15 seconds.

·         Disconnect the bypass tool.

·         Start the excavator from the operator cab and run the engine at low idle for 1 - 2 minutes without operating the hydraulics.

·         After operating the engine at low idle, operate the hydraulic systems several times or until air is purged from the system. Avoid running over the relief valve setting at the end of cylinder stroke.

·         With the excavator parked on a level surface, check and fill the hydraulic reservoir as required. Check for hydraulic leaks.
So it was asked, "Is it was possible to complete the testing, give in the bobcat manual, with the 30gpm flow meter that was us on the winch and windlass?"
My answer would be, yes. We would be able to do it, but you will be pushing the limits of the gauge. The problem is that the pressure gauge that's hooked with the flow meter goes only up to 3500psi. In the manual, they have you set the main relief valve at 3550 + or - 75psi. So with that window of 150psi you could get away with setting the main relief valve as low as 3475psi. Again that you are getting close to the limits of the gauge.

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