Rip Van Spin Testing Machine!

[WConley]

Hi guys.  After a few years of slumber, my spin testing machine has broken cover.  Robert Pond called me a few months ago wondering if I'd be interested in spinning up one of his new SOHC heads and testing a beehive spring combo.  He's about an hour away from me in Riverside, CA.

Heck yeah!  I've been bumping into that poor thing in the back of my garage for quite some time now...  It needed a lot of attention, since the previous testing thrashes had taken their toll.  My tachometer was broken, and the oiling system was springing leaks all over.  I also built an improved mounting plate for the SOHC head.

We agreed to do the testing at his facility.  Last Saturday, I packed the machine up in the ole' Ranger and headed over.  Robert has a forklift, which made the unloading easy:



Here's Robert's head getting set up for the test.  I must say it is a VERY nice quality casting.  All of the machining is accurate and all of my parts bolted right up as they should:



Here we are nearly set up for the first run:



We first ran the machine at idle speed to make sure all systems were operating normally.  This caught a loose bolt on the cam snout pulley, which would have gotten ugly at 8,000 rpm.  Once tightened up, I shot this little clip:

Dang it- Embed not working from Photobucket.  Here's the link:

http://s905.photobucket.com/user/ottodyn/media/Robert%20Pond%20Spin%20Test/TestMachineIdling_zps747a38bf.mp4.html

Here's a picture of the spring and retainer.  Robert opted for a PAC 1555 beehive spring. 

- Seat load:  Approximately 180 lb
- Load at full lift:  Approximately 425 lb

- Approximate cam lift:  0.720 inch
- T&D Steel Adjustable SOHC Rocker



This is impressively light!  He also set the spring up extremely tight.  Basically if set the lash less than 0.020", you risk binding the spring ;-)

After the basic systems check, we ran up to progressively higher speeds.  Here's a video clip at the 8,000 rpm test goal speed.  I aplogize in advance for the video quality.  I'm a bit off my game with this thing and I think i got some oil on the lens.  Robert's big beefy cam caps also obstruct the view from my machine's standard view port.  Will have to rework that...

Here's the link again.  Sorry embed isn't working:

http://s905.photobucket.com/user/ottodyn/media/Robert%20Pond%20Spin%20Test/8000RPMSummaryVideo_zps03dae0e0.mp4.html

The beehive spring works very well at this speed.  Valve motion is well controlled and the tight setup damps coil oscillation quite nicely.  There is some spring rotation, likely due to the valve stem wiggling/ orbiting in the guide.  That's not a big deal since these speeds will only be seen for short periods.

The smoke coming from the valve stem / adjuster interface is caused by the adjuster scrubbing across the valve stem tip.  It's unavoidable with this valvetrain geometry and an elephant foot adjuster.  Robert and I are not concerned about this because, again, the engine will rarely venture into this rpm territory.  It's only above 7,000 rpm that we start seeing significant heating from this effect.

By the way, here's the result of an earlier test where I ran a head for an extended period (like five minutes continuous) at 8,000 rpm:



The test was done with the same T&D steel adjustable rocker that Robert is using.  Notice the discoloration in the picture below.  The pivot ball underneath was badly chewed up from heating and lack of oil:




On Robert's test, we didn't come close to hurting anything.  We were only at 8,000 rpm for a few seconds.


Here's one of Robert's heads in a box.  Cammer goodness!



More boxes full of cammer goodness!



I spent a great day with Robert.  He is a super nice guy and I wouldn't hesitate to do business with him!

Now I'm getting fired up to do some more testing.  Jay may have a couple of devious plans for the near future.  Stay tuned...

- Bill

[WConley]

Forgot to mention - The valves are Ferrea hollow stem lightweight versions.  Robert says that he's getting 400CFM flow with this setup.

He'll be putting an engine on the dyno soon.  The spin testing has given Robert the confidence to take the engine to its full 8,000 rpm speed potential on the dyno.


- Bill

[machoneman]

Thanks Bill and a great test for sure. Nice looking head there as well. Funny, those beehives look so tiny it almost appears they can't hold a Cammer intake...yet they do.

[KMcCullah]

That's cool Bill! When you say 8000 rpm, your actually talking about crank rpm, correct? So the machine is turning the cam at 4000 rpm?

I know squat about the SOHC arrangement, but it seems like a rocker arm with a roller on each end would cure the scrubbing/smoking issue. A buttload of different sized lash caps would be a necessary evil though.

[WConley]

Hi Kevin -

Yes you are correct.  The cam was spinning at 4,000 rpm.  I use crankshaft speed in my terminology because that's consistent with what everybody else talks about.

As far as a double roller rocker, Barry Robotnik already had a few made at T&D.  I have one and I tested it up to 11,500 crankshaft rpm.  The rocker worked great, but I had a bolt back out of my cam cap, which broke the rocker shaft :-(



Yeah the lash caps would be a necessary evil. Once set though, Adjustment would be very infrequent.

[KMcCullah]

Oh wow! Mr Barry beat me to it. But that is exactly what the one in my head looks like. Honest..... 

Strange things happen at mega rpms obviously. Bolts come loose, metalurgy gets tested. This is all very fascinating to me.

I'm picking up a extra lotto ticket tonight. Maybe I can be the first guy with a cammer in a F250 bump side mud racer. 

[Qikbbstang]

 what is (normal/acceptable)?....... Maybe you have an old video of poor spring control?..... Also stumped on why there would be oscillation with the minimal clearence you mentioned, I thought that would have a dampening effect. Truely a treat to watch!

[jayb]

Hoping to get my new cams this week, Bill.  When I get them I'll put one in the test head and send it your way.  It will be interesting to see the effects of reducing the base circle on the RPM performance...

[WConley]

BB - There's always going to be some coil resonance, especially at certain rpm that correspond to natural frequencies of the spring.  "Acceptable" is a very subjective thing.  If the valve bounces up off the seat after it lands, the engine leaks compression and loses power.  Likewise if the middle coils vibrate violently, the spring can prematurely fatigue and fail.  That one is tough to quantify.  Here's a really good video I shot showing valve bounce with a weak spring.  This is clearly "unacceptable".  The valve is not in control:

http://s905.photobucket.com/user/ottodyn/media/ValveBounce-7125RPMComp930Spring8440Cam_zps7137d133.mp4.html

Setting the spring tight does help dampen these oscillations out, but it can't eliminate them completely.  This is because the coils are only tightly together at full lift.  When the valve stops on the seat, the coils are open and want to keep moving in the close direction.  Likewise, when the valve accelerates off the seat, the coils are still open and don't all accelerate at the same rate because of inertia.  This leads to the coil oscillations you see.

Having the coils tight at full lift helps a lot, as I already mentioned.  Beehive springs help a lot too because each coil is a bit smaller than the one below it.  This causes each coil to have a different natural (resonant) frequency, which breaks up the big destructive spring surge motion that traditional springs can exhibit.  It's like the old rule of having soldiers march out of step on a bridge...

Traditional springs sometimes use tightly fitted secondary springs and / or dampers to reduce coil oscillation.   This works too, but the rubbing motion heats the springs quite a lot.  You need plenty of oil on those or they get scary hot at high revs.

- Bill

[WConley]

Jay - Sounds good on those new cams.  Let me know!

- Bill

[Qikbbstang]

in operation. Smokey ran a strobe and that "froze" the action so the naked-eye could follow it. He pointed out that seeing the valve springs/retainers spinning was an indication of valve float. I recall he then proceeded to over-rev the valvetrain and indicated control of the springs was failing more and more on up until they smoked and supposedly glowed.  Looking at Bill's valves spinning with Smokey's performance in mind, it dawned on me that Bill's video is not the sum of strobes that "froze"  the valvetrain action, as I had seen with Smokey's Spintron but rather the actual rapid occurance that was captured at high speed and slowed down. That's a big difference. Thinking how much valve rotation occured in Bill's videos brief time leeds my to believe the valve, retainer and spring is very likely turning some really significant rpm's themselves...Can anyone say?.....
  When I think that this sinning and harmonics all occurs at 8,000 rpm to an OHC motor (cam rotating 4,000) with state of the art springs, it shocks me to dream up that even a standard production hot street OHV motor that sees 6,000 (Cam turning 3,000) is not all that far off in the hell whipped up on it when you realize that the OHCs valvetrain is no where near any form of the ideals to control damping.