Oil Pump Breaks on Dyno-Torsional Harmonics?
Oil Pump Breaks on Dyno-Torsional Harmonics?
(OP)
When dyno testing SBC sprint car motors on a Superflow X test dyno we are breaking the cam driven Dailey Engineering engine oil pump. It can happen on the first or second pull. The allen head screws break that hold the drive gear on the lobe and locks up the pump. Sprint car motors do not run a harmonic balancer. Do you think torsional vibration is causing this issue? Any ideas how to cure this issue. I have attach the link to vibration spectral data.





RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
What oil pressure does it have before it breaks.
Is the oil circulation hooked up right.
Regards
Pat
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RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
You mention the "allen head screws break that hold the drive gear on the lobe". Are you talking about screws that hold the timing gear to the two-lobed rotor in the rootes type scavenge sections? As for the pressure pump elements, I believe Dailey uses steel gears.
There's a couple things you should check. First, I would recommend putting a match drilled and press fit shear pin through each scavenge rotor and its timing gear, if there is not already one present. Screws are no good for taking shear if there is any clearance.
Second, I would make sure that you have enough open space past each main web area in the crankcase to allow air to easily flow back and forth as each pair of pistons pumps up and down. That will minimize the variations in pressure the scavenge pump sections see, and thus minimize the torque spikes on the scavenge rotor attachments.
If what you truly have is some torsional dynamic issue, then you are going about fixing the problem correctly. You are studying the data before coming to a conclusion. Unfortunately, diagnosing and correcting a torsional vibration problem usually involves lots of complex analysis followed by lots of tedious testing to validate your analysis.
If your pump is breaking due to a coupled torsional mode that is being excited by something in the cam drive, you'll have to figure out how to modify your pump's torsional dynamic characteristics to move that particular mode up or down in frequency so that it is out of range of the cam drive's exciting frequency.
If you have the time and patience, try machining one of the parts in the pump drive to make it slightly less stiff in torsion. This small reduction in torsional stiffness will lower the troublesome frequency, and may be enough to move it out of the critical range where it is coupling with the cam drive.
Shaft dynamic issues can be a nasty problem to solve. I've seen these type of problems cause endless headaches even for very bright engineers.
Good luck.
Terry
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
Also, 30g at 250 hz is a bit on the high side frequency wise to cause problems.
It could be TVs, how is the camshaft driven by the crankshaft?
Cheers
Greg Locock
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RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
http://www.daileyengineering.com/oilpumpmain.htm
I'm guessing the screws, or the joint they're supposed to clamp, carry half the torque of the scavenge pump.
Lack of preload or lack of Loctite could do that.
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
I can't find evidence that Dailey makes a pump driven by the usual skew gear distributor drive.
I thought maybe raptor was talkng about a pump driven by a belt from the camshaft front, e.g. like an LT-1's waterpump drive.
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
Maybe raptor could tell us what he means?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
Two, if theres no damper then the crank you are using must weigh a ton or so? Why no damper?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
They normally have a very light flywheel and no balancer so that they can accelerate and decelerate as quickly as possible.
Some years ago, there were scavenge pumps available that bolted to the timing cover and were driven by a coupling directly of the front of the cam. A ger drive was recommended over the stock chain drives typical of the OEM equipment in the engines of choice, being predominantly Small Block Chevys.
The OP is so unclear, I still have not decided if it is a pump driven of the front of the cam, a pump driven by the distributor drive on the cam or an eccentric like a diaphram type mechanical fuel pump. Unlike Mike, I couldn't be bothered doing a Google search to compensate for the lack of information in the OP.
Regards
Pat
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RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
I'd bet the dyno crew filled the crankcase instead of the oil tank.
I.e., not a harmonics problem.
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
How is the timing cover located.
Has the block been align bored.
Regards
Pat
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RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
One thing I did not mention is that the Dailey pumps brake where another "stronger" brand/style of oil pump does not. He has a lot of customers running the Dailey set up.
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
If it has been align bored, it is sometimes necessary to realign the dowels holes on the timing cover to keep the crabkshaft seal concentric on the crank.
Regards
Pat
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RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
We haven't seen a fracture surface.
Mike Halloran
Pembroke Pines, FL, USA
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?
RE: Oil Pump Breaks on Dyno-Torsional Harmonics?