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.
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Oil Pump Breaks on Dyno-Torsional Harmonics?
- Thread starter raptor04
- Start date
patprimmer
New member
The link is wrong.
What oil pressure does it have before it breaks.
Is the oil circulation hooked up right.
Regards
Pat
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What oil pressure does it have before it breaks.
Is the oil circulation hooked up right.
Regards
Pat
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raptor,
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
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
GregLocock
Automotive
20 to 30g is enough to break things, but I'm surprised its enough to break steel things straight away.
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
SIG
lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.
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
SIG
lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.
MikeHalloran
Mechanical
I think he's talking about screws that hold the phasing gears on the end of a two-tooth gear pump that resembles a Roots blower.
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
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
Thank you MH for the link. The pictures show the type of pump I suspect everybody thought raptor was referring to. I don't think anything about this pump could be described as "cam-driven" etc. I think raptor must be talking about a "traditional" Chev oil pump drive that comes from a gear on the rear end of the camshaft (and also drives the distributor). I don't think "torsionals" etc. would affect a pump driven by a rubber cogged belt.
MikeHalloran
Mechanical
Well, now it's a puzzle.
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
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
MikeHalloran
Mechanical
That would be a good start.
Mike Halloran
Pembroke Pines, FL, USA
Mike Halloran
Pembroke Pines, FL, USA
patprimmer
New member
A serious Sprint Car engine Does ave a very light crank with centre counterweights removed, undercut counterweights, hollow big ends and rifle drilled mains.
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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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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
MikeHalloran
Mechanical
Note that the scavenge pump has a very high capacity, and no relief valve.
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
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
- Thread starter
- #14
Thanks for everybody's input so far. I am checking with the engine dyno tester for some answers to your questions. The oil pump is mounted to the front of the timing cover, inline with the cam, driven from the cam gear. The timing set is gears NOT a belt or chain. The picture/link of the oil pump looks correct, but with 3 stages, I believe.
patprimmer
New member
Are the pump and the drive and the cam all perfectly aligned.
How is the timing cover located.
Has the block been align bored.
Regards
Pat
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How is the timing cover located.
Has the block been align bored.
Regards
Pat
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- Thread starter
- #16
patprimer, I believe the timing cover is CNC'd for the oil pump mounting, aligned the best it can from the CNC-ing. The cover is located by the timing cover locater pins. Yes the blocks are line bored.
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.
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.
patprimmer
New member
Just because it's CNC'd does not mean it has to be correct. You may need to turn up a gauge to test alignment.
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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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
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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- Thread starter
- #18
MikeHalloran
Mechanical
Sheared? Not in evidence.
We haven't seen a fracture surface.
Mike Halloran
Pembroke Pines, FL, USA
We haven't seen a fracture surface.
Mike Halloran
Pembroke Pines, FL, USA
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