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flywheel to balancer weight proportion- inline 6

General engine tech -- Drag Racing to Circle Track

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Kevin Johnson
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Re: flywheel to balancer weight proportion- inline 6

Post by Kevin Johnson » Sun Aug 11, 2019 2:31 am

viewtopic.php?t=16279

Lots of information in the above thread. Good luck.

enigma57
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Re: flywheel to balancer weight proportion- inline 6

Post by enigma57 » Tue Sep 10, 2019 2:31 am

Building an inline 6 and will follow this thread with interest. Have a question......

Regarding overall flywheel weight as opposed to torsional dampner weight...... Is overall flywheel weight inclusive of clutch disc and pressure plate, as well? In my view, it would seem so.

Thanks,

Harry

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Re: flywheel to balancer weight proportion- inline 6

Post by digger » Tue Oct 08, 2019 5:07 pm

Is the consensus that the rod rotating mass is influential on the harmonics i.e it produces a similar effect to lumping the rod rotating component mass on the crank? This would theoretically increase the mass moment of inertia of the system without changing the torsional or bending stiffness thereby lowering the frequency.

what are peoples thoughts on the reciprocating mass and effect on the harmonics? since there is a variable sinusoidal relationship between translation of reciprocating motion to rotational motion, is it a variable contribution mass? i gather the absolute magnitudes are going to be relatively small compared to large items such as the flywheel and crank itself but the masses involved could total a few kg acting at upto a couple inches so the M*R^2 might not be trivial

where i'm coming from is does a lighter rod and piston provided a benefit in terms of raising the harmonic frequencies by any meaningful amount? i mean the effect is a stroke ^2 term so would compound so it would help to explain why large stroke performs poorer aside from the physical crank flexibility

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Re: flywheel to balancer weight proportion- inline 6

Post by Circlotron » Tue Oct 08, 2019 6:59 pm

enigma57 wrote:
Tue Sep 10, 2019 2:31 am
Building an inline 6 and will follow this thread with interest. Have a question......

Regarding overall flywheel weight as opposed to torsional dampner weight...... Is overall flywheel weight inclusive of clutch disc and pressure plate, as well? In my view, it would seem so.

Thanks,

Harry
I think overall weight is misleading. You could have two flywheels of the same weight (okay, mass...) and the one with the greater amount of mass near the edge would have a greater moment of inertia and therefore combine with the crank elasticity for a lower resonant frequency despite being the same weight as the other flywheel.

digger
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Re: flywheel to balancer weight proportion- inline 6

Post by digger » Tue Oct 08, 2019 8:18 pm

if you are talking the torsional deflection (twist) then its mass moment of inertia that is important, not mass.

i gather the issue may be a coupling of twist with a small amount of bending? in which case the translational mass (mass) is relevant to some extent

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Re: flywheel to balancer weight proportion- inline 6

Post by inline6 » Tue Oct 08, 2019 8:34 pm

When I was messing with large cubic inch 6 cylinder pulling engines, mind you this is all over 5" stroke stuff I was using the biggest balancer ATI had. I believe that is 8 1/4", I also ran everything as tight to the cover as I could both the balancer and flywheel. The flywheel and clutch seemed to be the easiest to achieve these guys liked hanging Crower clutches way the heck out there. Still struggled with harmonics turning a 4 main 6 cylinder pulling engine 6700rpm with a 5 1/2" arm, but really feel it would have been worse without the ATI and getting that balancer and flywheel tighter to the engine.
Scott
Tractor Puller, 1959 IH 460 with 430cid NA Alcohol Inline 6 started its life as a D282

The only replacement for displacement is RPM!

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Re: flywheel to balancer weight proportion- inline 6

Post by enigma57 » Wed Oct 09, 2019 3:43 am

Digger, Circlotron and Scott...... Many thanks for your thoughts on this. I believe I understand what you are all getting at and appreciate your thought provoking comments.

The vehicle I am swapping this 292 inline 6 engine into is my '57 Chevy sedan. Its not a race car. It will be a driver and I will occasionally tow a boat trailer behind it. As to function...... For all intents and purposes, think of it as a 3,500 lb. truck.

Being an old coot and this being both my last build (and my first inline 6 build)...... I just want to do it 'right'. Have cammed the engine to produce a broad, nearly flat powerband from 2,000 RPMs to peak and make max average power and torque up to the point where these long stroke engines begin having harmonics issues. Have no plans to exceed that RPM. Just want to build this so it will stay together and not sling the flywheel off if I wind it out a bit.

To that end, I have here, a 30 lb. (14-1/4", 168 tooth) billet steel flywheel and one of the 8" GM malleable iron torsional dampners (will need to get an exact weight, I believe these weigh around 12-1/2 lb. without drive pulley attached). If I can work out the added length with respect to space for the radiator, would like to run this dampner/balancer (or perhaps one of the ATI or Fluidampers) rather than have the engine drive-belts driven off the outer ring of the dampner as the OEM inline 6 setup does.

My transmission is a heavy duty T-85 Borg Warner 3-speed with overdrive which was original to a '65 Ford truck. From past experience, these are strong transmissions (I had one in a '55 Chevy many moons ago), but the gears are large and heavy so there is nothing to be gained by power shifting them except to unnecessarily screw up the 2nd and 3rd gear synchro rings. That being the case, I am planning on running either a heavy duty 11" or 12" diaphragm type truck clutch.

Will use lighter pistons and rods to take some weight (nearly 3 lbs. in total) off the reciprocating parts and balance the heck out of it including indexing pressure plate to flywheel. The idea being that the bad harmonics/crank twist and deflection are partially a function of both stroke length and reciprocating weight and since stroke will remain at 4.10"...... Removing 1/2 lb. reciprocating weight from each crankshaft throw should at least help.

That's the plan, anyway. I believe I understand the concepts of which you speak with regard to mass, inertia mass nearer (or farther) from center of rotation, etc. In this instance, do you think it would be more beneficial to have the added frictional area (and clamping force) of the largest dia. clutch I can fit inside the bellhousing (12")...... Or stick with an 11" clutch, as I believe the towing duty will demand more than a 10-1/2" clutch is capable of, long term...... These being single disc clutches. Next question...... If it would make a significant difference for the better as far as moving inertia mass nearer to center...... Given the intended use of the car...... Should I consider a dual disc clutch of smaller dia. than 12" or 11"?

I understand your meaning regarding the concepts discussed. Will follow with interest and do what I can to apply them to the running engine. I simply have no way of quantifying them mathematically. So cut me a huss on that and I'll do my best to comprehend your meaning as the discussion progresses. Did well in school until I discovered beer, fast girls and faster cars at age 15. Did not go to college. Have only a high school education plus some technical schools for NDT (welding inspection) whilst in military service.

Best regards,

Harry

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Re: flywheel to balancer weight proportion- inline 6

Post by Kevin Johnson » Wed Oct 09, 2019 7:27 am

Harry, if you are going to run an or the OEM damper, be sure to have the rubber renewed or buy a new one.

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Re: flywheel to balancer weight proportion- inline 6

Post by inline6 » Wed Oct 09, 2019 8:42 am

Harry,
There is a guy in Washington state I have used with success on renewing the rubber. You have to plan ahead as he takes summers off and ever other month off. But the couple I have had done have came back nice. Also your chain drive to the cam right? This is another thing that I think we struggled with transferring harmonic from the valve train to and from through the gear drive.

A billet fully counter weighted crankshaft will help alot. :D

Scott
Tractor Puller, 1959 IH 460 with 430cid NA Alcohol Inline 6 started its life as a D282

The only replacement for displacement is RPM!

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Re: flywheel to balancer weight proportion- inline 6

Post by enigma57 » Wed Oct 09, 2019 8:19 pm

Thanks, Kevin and Scott! I'll keep that in mind. If I do run the GM malleable iron torsional dampner, it is new. Been sitting in its box for about 20 years now. Was going to run it on a V-8, but that project took another direction. Would ATI be a better way to go for this inline 6 build?

The Chevy inline 6 uses cam gears, so no chain. Yes, a fully counterweighted billet crankshaft would be a dream come true. If I could afford that, I'd destroke the 292 from 4.10" to 3.875" which along with the lighter pistons and rods should help with the harmonics a bit. I did contact a fellow who would do a custom crank for a reasonable price, but there is a 10 crank minimum and all must be identical. So out of my price range and I couldn't find enough guys to go in with me and do it.

As it is, I have (2) 292 cranks here. One is the '63 forged steel crank that has 6 counterweights. The other is a '67 and later nodular iron crank that has 12 counterweights. This is the one that I plan on using. Its a heavy piece. Weighs 73 lb. May look into lightening it a bit. Stock 292 rod and piston weighs 1635 grams. Longer Molnar billet rods and Ross pistons weigh 1405 grams including rings.

Best regards,

Harry

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Re: flywheel to balancer weight proportion- inline 6

Post by chevyfreak » Thu Oct 10, 2019 7:24 am

enigma57 wrote:
Wed Oct 09, 2019 8:19 pm
If I do run the GM malleable iron torsional dampner, it is new. Been sitting in its box for about 20 years now. Was going to run it on a V-8, but that project took another direction. Would ATI be a better way to go for this inline 6 build?

Harry
Hi harry.
If you do end up using the v8 balancer you can get past the v-belt groves by taking the sbc swp crank pulley and machine the id open to fit over the hub on backside of v8 damper. The v8 damper stands out more away from the timing cover on the inline. Enough to fit a 2row pulley. Just some spacers needed between the pulley and backside of damper hub so it tightens properly.

Did it on my 153. The original hub were toast. And with the tendency of shaking on the 153, i took a chevy v6 damper and fit pulleys behind it.

Chevyfreak.
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Re: flywheel to balancer weight proportion- inline 6

Post by Juho_ » Thu Oct 10, 2019 10:12 am

Wouldn't the heavier crank be better, if thinking about harmonics ?
73lbs crank is quite near the crank I have in my Volvo B6304 engine.

Journals are 50/65mm and weight 28kg (~62lbs), capacity being 2922cc.
No problems revving more than 8000rpm, flywheel and damper bolts hold-on well, no issues.

Tho, I have quite lightweight pistons and connecting rods (920g per cylinder combined weight if I remember correctly).
Flywheel is on the heavy side (with clutch disc and pressure plate about 14-15kg), but damper is quite large diameter (from a newer six cylinder variant, older engine has smaller but thicker and slightly heavier).

I asked some time ago about heavier crank and harmoics, and how the harmonics affect the engine and it's durability.
But I've recently heard about problems occuring when lightening crank on a six cylinder engine (BMW M30 race engine, at finnish BMW forum).
Then again no problems crank breaking, without lightening it.

I might know better next year, if I manage to re-build the engine better, and be able to rev it even more.
There was no point even trying higher rpm's because power started dropping after 7000rpm, but kept power till 8000rpm (8100rpm limiter) quite well so it was faster when revving further than e.g 7500rpm.

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Re: flywheel to balancer weight proportion- inline 6

Post by Chris_Hamilton » Thu Oct 10, 2019 11:21 am

Another question I didn't see addressed here. Would a fluid type damper be more effective? About the same? Worse? I've followed this post as I am in the planning stages of building 2 Nissan L6's. Far from an expert on engines, but I remember reading somewhere that traditional dampers needed to be matched to the harmonic range otherwise they were useless. And any alteration in reciprocating weight would change the range made it seem to me that unless you tested and verified at what range you were experiencing the unwanted harmonics putting a traditional damper on it was pretty much hit or more likely miss. Same article said a fluid filled damper was able to be effective over the entire rpm range. Sounds almost too good to be true. What am I missing? Thanks everyone.

Love this forum btw I can spend hours reading here. Learned a lot and realized how little I know. :D


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Re: flywheel to balancer weight proportion- inline 6

Post by enigma57 » Fri Oct 11, 2019 4:21 am

Thanks, Kevin, Chris, Juho and chevyfreak! Much to consider.

I believe that I will either use the OEM 8" malleable iron dampner I have here or pick up an ATI dampner. After reading more about the Fluidamper and changes that occur to the silicone fluid over time due to internal friction and heat, I believe I will stay away from that type dampner on this particular engine. Thinking back to my discussion with Mr. Molnar some time ago when I was considering a custom crank..... I asked him about dampners to run with the custom crank and he recommended ATI. Did not elaborate, but I had the distinct impression that he would not recommend a fluid type dampner for what we were discussing.

Chevyfreak, that is a novel way to work out the drive belt placement and I will give it some thought. The issue being overall length of engine versus room for radiator in my '57 Chevy sedan. The Chevy inline 4 is the same in that area as is the 194, 230 and 250 inline 6. Also the same as the 292 inline 6 except for the 292 block having a taller deck. What I must consider is...... Will the end result shorten overall engine length sufficiently to warrant doing it this way. And (perhaps more importantly with the tall deck / long stroke 292)...... Will spacing the heavy 8" dampner forward on the nose of the crank snout weaken the crank snout over time and will doing so result in less than full engagement of the key that fits in keyway on crank snout.

Right now, the plan is to have the timing gear that fits onto the crank snout countersunk 0.25" on the front side so the uncut V-8 dampner will go back as it should. The other way being to take 0.25" off the rear of the dampner sleeve that fits onto the crank snout. I am thinking it would be better to countersink the crank gear so that the heavier dampner will have full engagement with the key and keep the weight as far back as possible. Then bolt a small block Chevy V-8 (short water pump type) double groove pulley onto the dampner hub. To align the drive belts, I can machine a spacer that takes up the needed distance between block and water pump and redrill the alternator bracket to allow it to mount the same distance forward as well. Would need to make provisions to accommodate other accessories if I install A/C or power steering at some point. No plans to do so at present, though. And in any case, will need to bring engine to TDC on #1 cylinder and install a new timing pointer (spot weld to timing cover).

I will give your idea some thought, however. If it will shorten the engine enough to help fit it in my chassis and will not place undo strain on the crank snout, I may give it a go.

Best regards and many thanks to all,

Harry

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