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#14042 - 07/14/17 05:47 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Originally Posted By: dcb

The end of one



I had occasion to inspect the shards of the impressive explosion pictured above, and although I was able to determine the exact cause of the failure, I'm not going to comment specifically about it. I do have a few thoughts that I am going to share. They are in the form of a quick note of pertinence to all who are vintage and historic racing ageing iron, from ANY manufacturer:

A) You can, of course, utilize stock parts in your "performance" or "racing" engine. You will want to be careful about the stresses to which you will subject the "stock" parts. Those parts won't like it very much, and they will like it less the higher the "Critical g Loads" are.

Some conservative guidelines:
1) High performance OEM parts ~3,800 g's
2) Modified OEM parts ~3,500 g's
3) Street stock parts ~3,200 g's
4) Engines KNOWN for weak parts ~2,800 g's

If you have decided to go the stock parts route, take the time to evaluate how highly "loaded" the parts will be at your anticipated "level of performance". If you are unable to judge this for yourself, consult someone qualified to review your choices . . . . . . .

2) You WILL need to track, or at least approximate, the number of cycles to which you are subjecting the parts. Tolerable cycle life will vary, based on the "load" applied. Review the section about cycle life Vs load on my Racing Engines thread on this board. Useful part life is NOT infinite, even with the best quality parts. And it is even more "finite" using the stock bits . . . . .

d) You also need to be careful about "improvements" made on some components, when there are no other "upgrades" to other systems or components. There needs to be a "balance", spread along the load carrying capability of ALL components.

z) AND, it is also important to point out that my buddy Newton wins this argument, (F = m*a), EVERY TIME. Forces increase at the rate of the SQUARE of the speed increase. Ie: F @ 8,000 rpm = (F @ 4,000 rpm) x 4

Again, if you are unable to judge this for yourself, consult with someone qualified.

And as a final, and more practical note, engines producing less rpm & stress, are going to make LESS bhp per liter than engines producing more rpm & stress. That's just the way it is . . . . . .

Cheers
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14050 - 07/18/17 07:05 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: fordboy628]
dcb Offline
Champion

Registered: 01/24/11
Posts: 983
Originally Posted By: fordboy628
[quote=dcb]
The end of one



I can't look at this without remembering that after I pulled off the track, I tried to restart.... smirk

Dave

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#14051 - 07/18/17 11:23 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
JFW Offline


Registered: 01/16/11
Posts: 2095
Loc: Florida
Originally Posted By: dcb
[quote=fordboy628][quote=dcb]
The end of one



Never saw one "blowed" that bad.

I'll bite, what went first?

Obviously the center main bridge is torn out and the side of the block is blown away.

The rods look intact. Look like modified stock rods, BTW.

No billet 4-bolt center main cap.

Stock cap screws rather than ARP studs.

Can't tell what the crank is but it doesn't look like anything special.

This looks to me like a 7000 rpm motor at best.

Did the block just give out...the newest of these are 40 years old and who knows where they have been during that time. Many of us were recycling old blocks 20 years ago that had been racing motors before we got them. I doubt if there are any low time street motor cores to be found these days.

How many high stressed cycles are in these old piece of crap castings?

I think it is crazy to keep developing the breathing and ever increasing RPM/HP numbers and packing it all into these blocks that have aged out.

What do they say about insanity?

Glad my last A-series motor is 15 years in my rear view.

BTW, Dave Taber built some of the best ones we ever used but they were perhaps 135 HP/7800 motors. All built with Carillo rods and special cranks, BTW. Never had one of those blow. Just freshen with new bearings every third race weekend and you were good to go.

Just my thoughts from the peanut gallery.
_________________________
Jack Woehrle

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#14052 - 07/19/17 01:56 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: JFW]
dcb Offline
Champion

Registered: 01/24/11
Posts: 983
Jack,

There may be some disagreement as to what went first so I'm going to leave it at that. We all have come to this point in time with different experiences and superstitions.

This motor was my old vintage motor with an SCCA legal head... one that I ported and was probably not the best flowing head out there. I just wanted to get through a couple of race weekends before I ran the Tabor motor, and I made it... barely.

In a previous life, I ran motors just like this one very successfully. If memory serves me, I ran the entire 80's with one block, crank, rods and head. The combination was very reliable and at the time very competitive. I think that Gary Johnson ran it for a little while longer with success. So this massive failure baffles me a bit. What's not seen is the fact that all the bearings looked very good, and none of the fasteners failed.

Since I got back into racing - vintage racing - I've had two block failures in the center main web. the first was a thin flange block so I kinda expected it to fail. The second was not and really confused me. In both cases I noticed the oil pressure fluctuate and I pretty much knew what it was all about so I pitted with still running motors. Upon disassembly both had cracked cranks which I attributed to all the flexing they must have done with the center main web moving around. In all cases there was no real signs of detonation in the traditional manner - the rod bearings looked great and the piston crowns were normal. As I think about it. the pistons in this blown motor were the ones I started vintage racing with in 2007!

I've always been a low budget racer so billet stuff was always only a dream, but now the Tabor motor has all of that and more, so we'll see what happens at Road America in a couple of weeks.

Dave Brown

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#14053 - 07/19/17 06:05 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
The explosion of Dave's 1275 originated with a crankshaft fatigue failure. Of this there is no doubt. The origin point was in the connecting web (arm) between the #4 rod journal, and the #3 main journal. This is evident from the very prominent, fatigue marks ("beach lines").

Further, when the crank became a "2 piecer" the mechanical interference between the still rotating (at very high rpm's) crank parts, caused an instantaneous overload failure of the "case" (block) since the case was unable to contain the amount of energy being dissipated. ALL of the failed block parts give every indication of "instantaneous failure" under inspection.

A 4 bolt center steel main cap with say, ARP studs, MAY have reduced the "carnage" somewhat, but I have some serious doubts as to whether the destruction would have been much less. But certainly, a 4 bolt steel center main cap is a wise "investment" in any "high output" BMC engine.

My previous comments regarding cycle life, as well as the concerns both Jack and Dave raised, should be heeded by racers attempting to "squeeze more life" out of used racing components. Eventually, you will pay a price, one way or another.

Jack, there are some "new to racing" BMC parts out there. I, for example, have a complete thick flange, tufftrided crank, heavy duty con-rod, 1275 short block assembly sitting with my "stack of bits". I'm sure there are others out there, hoarded by lovers of vintage British iron . . . . . The trick is getting guys to part with them . . . . .

And additionally Jack, the "high flow, high rpm" engines you speak of are probably rooted in the "bar stool racing" of those who DO NOT dyno test, and therefore confuse the production of "noise" with the production of brake horsepower. If you watch the Saurino in car video of his SCCA Championship race, he is shifting at 7800 most of the time, occasionally to 8000. Now I'm not saying that there are NO BMC engines being wrung out to 9500 rpm. I just question whether they make any usable power there. The complete inlet tracts just DO NOT flow enough air to make peak power at 9500 rpm in a 1310 (1275 + .040" bore), when in LEGAL F/Production specification.

Just my opinion on the high rpm thing . . . . .
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14054 - 07/19/17 07:38 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
hoffman900 Offline
Champion

Registered: 02/03/11
Posts: 530
Loc: New Jersey
The NASCAR boys cycle out top of the line parts like Callies / Winberg cranks and Carrillo / Pankl / Lentz / Oliver connecting rods, but still good enough for 90% of the applications out there. OEM parts are no exception...

A friend of mine when racing at the top of the Nat'l Prod car scene in the '60s. For his car, 3 races on a set of connecting rods, 5-6 races on a crank. Mag them and cracks were showing. And this was when the cars were new! And people think racing today is expensive... Can you imagine buying a car off the showroom floor then having to replace the rods every 3 races and the crank every 5-6 races? The factory boys and those with factory connections could get them at cost or for free - imagine being a privateer. $$$

Most bottom end failures start with detonation. People will attribute it to oil or material failure, but detonation will kill rod bearings very quickly (and everything else will go downhill from there). IMO, most rod failures are incorrectly diagnosed and likely has more to do with the tune.

Most people still seem to think of dates starting with 2000. It's 2017. The 60s were 50+ years ago. This stuff is old and getting older.


Edited by hoffman900 (07/19/17 07:40 PM)

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#14055 - 07/20/17 02:34 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
rick haynes Offline
Amateur racer

Registered: 09/15/13
Posts: 169
fordboy

The highHP/highRPM motor vs the highertorque/lowerRPM motor debate is some thing Dave Brown and I have talked about for years. And what has made it interesting is
that we build the two different motors, have raced against each other and have seen the advantages of each type on the track , so it is not just a conflict of theories. I favor the highRPM/higherHP motors [7500-9000] with big lift/narrow cams,
Dave likes the lower lift wide cams that make better low end torque motors, I will guess 5500 to 8000 rpm. Granted not all the variables in chassis and gearing have been accounted for but they are known and have been mostly adjusted for to suit the best characteristics of each motor type. Dave runs a BMC C/R gear box giving give him a 3 speed on the track and generally a higher diff gear [ 3.9 vs my 4.2] I race a 4 speed dog box and because of the narrower power band I row my way around the track with my shifter. The results for me have been surprising and also disappointing at times too.
There are places on different tracks where , when both cars are at the sweet spot
of their very different combinations that the cars acceleration rate appears near dead even. and also much to my frustration times when Daves car is faster. I have noticed that while being behind Dave 2 time and both times we were going uphill on the track. On paper my car has more HP and a higher peak torque number too but at times it does not show it self in moving the car down the track. Why is this? My guess is there are the odd speeds and RPMs that Daves combo just works better at putting more power to the rear wheels , be it HP or torque, at just the right time.
So which is better? The two things that are always true is you have to be in front to win, and passing is done on the long straights with evenly matched cars.
And top speed, with the proper gearing, requires HP. So that is why I chose the way I do. I am sure it comes from all the years of racing at Road Atlanta, where top speed in the dip was required to win.

rick haynes



Edited by rick haynes (07/20/17 02:36 PM)

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#14056 - 07/21/17 05:58 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Rick,

My racing engine experience is wide, with portions spent providing engines to both the "club" racer, and to "professional" teams. What is consistent overall is:

Power available wins out, every time.

No BS about torque, or traction effort, or other such distractions. Acceleration is dependent on the amount of power available, once all the drag components are subtracted for a particular engine rpm/road speed. When bhp available = total drag, that is your top speed, pretty much regardless of gearing. There might be a small differential in engine rpm (say 300/400 rpm) with very fine (say 1 tooth) gear ratio "splits", but the top speed typically remains the same.

It is also important to note that top speed is roughly a function of the bhp cubed!! (BHP³) Since it is unlikely that any sort of class legal engine modification(s) can achieve those types of power increases, significant importance should become focused on reducing the drag components.

Professional teams have the "luxury" of being able to build engines to differing specifications, engineered to provide specific bhp curves, tailored to the requirements of certain types of race tracks. Amateur racers typically do not enjoy this "luxury". And, as you astutely pointed out, this difference in engine performance, coupled with differences in gearing (and therefore acceleration), are what you and Dave are experiencing on the race track.

If you, (or anybody else), wants to dig deeper into the gearing puzzle, here is a link:

Selecting gear ratios

Cheers
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14057 - 07/21/17 06:09 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Originally Posted By: dcb
Originally Posted By: fordboy628
[quote=dcb]
The end of one



I can't look at this without remembering that after I pulled off the track, I tried to restart.... smirk

Dave


Well: Hope springs eternal.

I have always found racers to be the biggest optimists on the planet . . . . . .

Cheers
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14059 - 07/21/17 06:12 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
rick haynes Offline
Amateur racer

Registered: 09/15/13
Posts: 169
fordboy

"When bhp available = total drag, that is your top speed, pretty much regardless of gearing. There might be a small differential in engine rpm (say 300/400 rpm) with very fine (say 1 tooth) gear ratio "splits", but the top speed typically remains the same."

Read this a few times and not sure I get your meaning other than the obvious. Given that total drag of the car in question is a unknown for all but pro teams, arriving at a cars top speed has to be done more practically. That is, it in necessary to match the final drive with the particular characteristics of the longest straight on the track. The 7% difference in a 3.9 and a 4.22 changes where the total drag meets my max HP on my power curve, I have a higher trap speed a Midohio with a 4.22 over a 3.9.
in other words my available HP to the rear wheels at 8800 rpm multiplied by a 4.2 diff. over comes more drag than 8200 rpm running through a 3.9 final drive. so I would disagree with you final statement.
Lower acceleration with the higher 3.9 is a small factor[ but only very slightly] as all the gears would be spaced a little farther a part so as to have the same over all 1st gear ratio.

rick haynes

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#14060 - 07/22/17 09:59 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: rick haynes]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Originally Posted By: rick haynes
fordboy

"When bhp available = total drag, that is your top speed, pretty much regardless of gearing. There might be a small differential in engine rpm (say 300/400 rpm) with very fine (say 1 tooth) gear ratio "splits", but the top speed typically remains the same."

Read this a few times and not sure I get your meaning other than the obvious. Given that total drag of the car in question is a unknown for all but pro teams, arriving at a cars top speed has to be done more practically. That is, it in necessary to match the final drive with the particular characteristics of the longest straight on the track. The 7% difference in a 3.9 and a 4.22 changes where the total drag meets my max HP on my power curve, I have a higher trap speed a Midohio with a 4.22 over a 3.9.
in other words my available HP to the rear wheels at 8800 rpm multiplied by a 4.2 diff. over comes more drag than 8200 rpm running through a 3.9 final drive. so I would disagree with you final statement.
Lower acceleration with the higher 3.9 is a small factor[ but only very slightly] as all the gears would be spaced a little farther a part so as to have the same over all 1st gear ratio.

rick haynes


Rick,

Your example uses single point rpm samples. It is apparent from your performance, that your engine has a higher average bhp available in the overall range of rpm you are utilizing (the higher rpm one) Vs the lower rpm sample. And, as you point out, the 4.22 diff gives you a 7+% acceleration bonus. Also important, is your track record of keeping your engines INTACT at elevated rpm's . . . . .

My example was about situations where the gearing is already almost optimum. The point being that once you are close, small changes (1% or 2%)don't accomplish much. 7% though, is a BIG change. What I'm trying to accomplish is to get racers to think about broad(er) concepts like: average bhp over the usable rpm range, Vs peak bhp at a certain rpm. The contents of the book, Vs one page, so to speak.

I think we are both in agreement and on the same page here. We are just using differing examples. And, BTW, I would ALWAYS endorse a change that reduces lap times at a road race venue, since getting to the flag first is the point. USUALLY, lap times will fall when top speed increases. Production cars typically need to go the top speed route to reduce lap times, since rules prohibit the kind of aero mods that greatly increase corning speed. Not that aero is unimportant, SCCA just doesn't give you too much leeway. I think we probably agree on that as well.

As far my thoughts on engine rpm range theory goes, I'm with Sir Harry Ricardo:

He who can modify his engine to maintain higher rpm's, will benefit thereby.

Just as true today as was in 1922 . . . . .

Cheers
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14061 - 07/22/17 11:22 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 766
Loc: Greenville, SC
Snapping stock cranks in a 1275 is a story any long time 1275 racer will have to share, if they do it long enough, but I have seen at least one Moldex that did the same thing, but the racer in question was trying to shift at 9500. As Mark says everything has it's limit. We have not seen as many stock type cranks snap in the SCCA limited prep HP engines, the biggest difference other than HP when compared to SCCA full prep motor is they turn a good 1000 less rpms. Hard to predict a crank failure, I seen guys turn stock modded cranks 8000+ rpms for years of racing and then again, I seen them break in a handful of events. No doubt a billet crank buys more insurance. I try when building a serious high rpm race engine to use the early 1275 blocks which are solid under the center main, and after seeing Dave's cracked center main webbing, it just reinforces that decision. Another crank choice for the budget minded racer is getting your hands on the early EN40B crank, but it is so damn hard, it is way more difficult to lighten, and I mostly shy away these days from wedging EN40 B cranks, due to the fact it makes longer on a manual mill to do (smaller cuts) and it takes harder, and more expensive end mills to do it, and more of them, so you can easily use up $200-300 in end mills doing it.

I will put this out there as well, the last Moldex billet 1275 crank I got (2015), was less than one ounce lighter than stock, the one before that was 3 pounds lighter than stock. Moldex uses manual only machinery, and they don't seem to be overly concerned about weight from one unit to the next, not a warm and fuzzy feeling when forking out the cash for a billet crank, so they would be low on my list as for a supplier of a billet crank. In short the Moldex of today is not the Moldex of yesteryear. The crank I got from BWR was a piece of art, but the lead time to get it was well over a year.


Edited by Hap Waldrop (07/22/17 11:29 AM)
_________________________
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#14062 - 07/23/17 11:28 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
hoffman900 Offline
Champion

Registered: 02/03/11
Posts: 530
Loc: New Jersey
The Moldex cranks still have a lot of material on them and can be paired down a bit. They're old fashioned designs as far as the counterweight goes. I think Ro-Dy does most of the work for them now anyway.

Marine Crankshaft (which is where BWR sources theirs) is as good and modern of a design as you're going to get for something oddball. Bryant and Winberg won't touch anything that isn't a high end purpose built V8 race engine.

Hap, I believe these are your photos:

Moldex:

Marine Crankshaft:


Here is one for a blank check FP 1500cc Super 7:
https://www.instagram.com/p/BO3cO5qA0Sef...chnik&hl=en


Edited by hoffman900 (07/23/17 03:40 PM)

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#14064 - 07/23/17 12:51 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: hoffman900]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Here is some "downtime" reading regarding crankshafts:

4 cylinder crankshaft thoughts

Cheers


Edited by fordboy628 (07/23/17 12:53 PM)
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

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#14065 - 07/23/17 03:43 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
hoffman900 Offline
Champion

Registered: 02/03/11
Posts: 530
Loc: New Jersey
Food for thought from Chris Uratchko. He builds a lot of high end 400+ci small blocks making in the 1000-1200bhp range.

Quote:
In my experience 1000 hp on a 38-42 pound crank is not a desirable situation. I have used 39-42 pound cranks in the past on that type of power level with 3.75-3.900 stroke SBC/SBF but I have changed my methods over the years and no longer desire cranks that light. Once you add center counter weights, and some mass to the crank in the right places they will end up in the 50+ pound range for a SB, give or take and that's where I like to be for any good hp and rpm SB.

I have stated many times and I'll keep saying it. One of my best/fastest SB's has a 58 pound Bryant in it. It's a big stroke tank but loves RPM, and my bearings love it too

Quote:
Folks used to focus on super light cranks, rods, pins, in the past... long time ago when 650 hp was a big number for a SB. Then the myths carried on into the late 90's when builders were set in their ways about component weight and while engines were making more and more hp. Next thing you know there are 1000+ hp SB's in the sportsman world with large strokes spinning 8500+ and the myth's kept on.... thin wall pins, light weight cranks and high piston speeds. Them days are over and nobody should be ordering light weight parts for these kind of engines.

There's no hp or acceleration in light weight parts when the stuff won't hold it's shape. Light weight rotating in the engine does not equal faster acceleration... urban legend in my experience

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#14066 - 07/23/17 05:54 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: hoffman900]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Originally Posted By: hoffman900
Food for thought from Chris Uratchko. He builds a lot of high end 400+ci small blocks making in the 1000-1200bhp range.

Quote:
In my experience 1000 hp on a 38-42 pound crank is not a desirable situation. I have used 39-42 pound cranks in the past on that type of power level with 3.75-3.900 stroke SBC/SBF but I have changed my methods over the years and no longer desire cranks that light. Once you add center counter weights, and some mass to the crank in the right places they will end up in the 50+ pound range for a SB, give or take and that's where I like to be for any good hp and rpm SB.

I have stated many times and I'll keep saying it. One of my best/fastest SB's has a 58 pound Bryant in it. It's a big stroke tank but loves RPM, and my bearings love it too

Quote:
Folks used to focus on super light cranks, rods, pins, in the past... long time ago when 650 hp was a big number for a SB. Then the myths carried on into the late 90's when builders were set in their ways about component weight and while engines were making more and more hp. Next thing you know there are 1000+ hp SB's in the sportsman world with large strokes spinning 8500+ and the myth's kept on.... thin wall pins, light weight cranks and high piston speeds. Them days are over and nobody should be ordering light weight parts for these kind of engines.

There's no hp or acceleration in light weight parts when the stuff won't hold it's shape. Light weight rotating in the engine does not equal faster acceleration... urban legend in my experience


I consult on a LOT of differing race engine applications, and guess what? The same rules of physics apply in ALL cases. Some very quick comments:

IMHO, reciprocating weight is more important to the ability to accelerate the engine quickly.

If rotating crankshaft MASS was a primary acceleration consideration, why to F1 and NASCAR engines use cranks with extra counterweights??? In F1, made of tungsten!!! Where the mass is located is far more important, as you will see later.

There's no hp or acceleration in light weight parts when the stuff won't hold it's shape.
Always true, AND, there is also no longevity in parts that will not hold their shape . .

Light weight rotating in the engine does not equal faster acceleration...
It depends Kemo Sabe. On how much lighter and where the center of mass is located. I know this is hard to believe, but it IS possible to have a lighter part with a higher moment of inertia.

For more thoughts and calculations on MOI, I direct you to my buddy Steve Fox's company: PowerTrain Technology. This link will take you to his pdf catalog. Read his notes about MOI starting on page 6.

PowerTrain Technology Catalog, on Moment of Inertia

BTW, Steve manufactures state of the art clutch and driveline components. You should be using his products . . . . .

Cheers


Edited by fordboy628 (07/23/17 05:55 PM)
_________________________
Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

Someone who thinks logically is a nice contrast to the real world . . . .

Top
#14067 - 07/23/17 06:03 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: hoffman900]
fordboy628 Offline
Professional

Registered: 06/30/14
Posts: 307
Loc: NE Illinois
Originally Posted By: hoffman900
The Moldex cranks still have a lot of material on them and can be paired down a bit. They're old fashioned designs as far as the counterweight goes. I think Ro-Dy does most of the work for them now anyway.

Marine Crankshaft (which is where BWR sources theirs) is as good and modern of a design as you're going to get for something oddball. Bryant and Winberg won't touch anything that isn't a high end purpose built V8 race engine.

Hap, I believe these are your photos:

Moldex:

Marine Crankshaft:


Here is one for a blank check FP 1500cc Super 7:
https://www.instagram.com/p/BO3cO5qA0Sef...chnik&hl=en


Gee, a couple of questions:

Which one do you think is stiffer or more robust?

And, be careful, trick question,

Which one needs a harmonic damper?

Cheers,
F/B
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Fordboy628

Without "data", you are just another guy with a theory or an opinion . . . .

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#14069 - 07/24/17 09:48 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
hoffman900 Offline
Champion

Registered: 02/03/11
Posts: 530
Loc: New Jersey
1) Ford 1500 > A series with dummy mains > A series (std). (stiffer to least)
2) All of them!

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#14070 - 07/24/17 09:51 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
hoffman900 Offline
Champion

Registered: 02/03/11
Posts: 530
Loc: New Jersey
Here is a good quote dug up from the internet:
Quote:
We used to do work for Comptune in Ohio here their specailty was litttle SCCA MG 4 cyl engines. FAST little MG's at that!!!!

Anyway, the dyno operator told us that at certain RPM's the 180* crank would "shake things up" a bit...well one day my boss stopped out at their shop while they were dynoing a customer engine and he said "that thing just about jumped of the stand"! I think the "bad" RPM was either 4500 or 6500 I cannot remember now, it was somewhere in there though. Good thing for them they were high RPM engines.

Now these little guys were on the ragged edge to say the least but the operator would not load them until they got past the shake. So in a nut shell I think the firing order/180* crank will cause some additional wear and tear.

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#14071 - 07/24/17 04:09 PM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
rick haynes Offline
Amateur racer

Registered: 09/15/13
Posts: 169
My observations and personal experiences with 1275 cranks are;

The EN40B cranks in high HP motors break more often than the 16
numbered cranks. I know they are harder and the EN40B steel is the better
material and all the billet race cranks in England are made from it. But
I have seen many of them broken and most break through the # 4 rod
journal. I have concluded it must have something to do with the EN cranks
having the rods cross drilled and it must be causing a stress point.

I have never used a damper on a 1275 and except for the following exception, have never had a problem with #16 or billet cranks. The reason is I have read too much conflicting
information on the subject and I dont believe the claims from the peoples selling them any way about all the HP that can be recovered. I think it is just more mass to spin.

I think lightened and wedged cranks may work better but they also crack
quickly. But as stated I don't use dampers ether.

rick haynes

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#14073 - 07/25/17 12:28 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: rick haynes]
dcb Offline
Champion

Registered: 01/24/11
Posts: 983
I agree with Rick about the EN40B cranks. They are the only ones I've had that failed magna flux. Of course I'm the guy with the gruesome picture that started most of this commentary.

My memory is a little shaky and perhaps unreliable, but I can't remember a bottom end failure from the seventies and eighties, but have had three major failures in the last 9 years. Now before you assume the compression ratios have increased from the eighties, I think we were above 14:1 once race gas was permitted.

Whatever, I don't see any future in putting together any more stock bottom end motors. I used to think they could be relied on, but the evidence has turned me against them.

I've pretty much revised everything on the car for next weekends Road America SCCA race. After a much more careful look at the suspension I realized I had really screwed it up. Mostly the issue was severe bump steer caused by forgetting that the MGB shocks have longer suspension arms than the stock shocks I used on the vintage car and on my old SCCA car. I've now got the bump steer down to around .020" throughout the usable range of travel. The other issue had to do with some ride height confusion which now seems to be resolved.

I've replaced the mystery on/off MSD ignition system with the Electromotive system which seems to want to stay ON. And of course there is the newly refurbished Tabor motor. And behind it is the completely gone through and freshened JSR gearbox.

Hope it all works. I've discovered that when you perform as badly as I have the last two outings, few people come over to talk and you get a little lonely.

Dave Brown


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#14097 - 08/15/17 09:15 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
dcb Offline
Champion

Registered: 01/24/11
Posts: 983
I feel obliged to offer some final comments on my SCCA Majors effort.... didn't work out so well. I went to the last race at Road America with some hope of getting a little closer to respectable and didn't come close.

I can't put the blame on any one thing except that I couldn't even walk away from an HP Honda Civic! On the brighter side, the bump steer issues were gone and amazingly I could even land on the exit bumpers and feel little or no wickedness. I think I've gotten the brake bias within range of being right as well. But that's it for positives.

The first qualifying session was my best. The temps and pressure were very good and stable - more on that later. The only problem I felt was that I had somehow screwed up with the HANS device and as the session proceeded it kept pulling my head further back. I finally came in when I could no longer easily look down at the gauges.... something about getting the harness buckles in the wrong place.

Started the race later that day and all of a sudden the temps were high - 250 on the oil - and after a few laps decided to park. I wasn't competitive anyway. That evening I had pretty much decided on packing it in, but in the morning my wife coaxed me into running the Sunday race. I went out for the Sunday qualifying and notice that the gauges were all good again... too good... they weren't even moving after a lap or two... they weren't moving at all. These are pretty high-end electronic gauges, I bought them as a gift to myself, and now they aren't doing anything. More electronic gremlins.

Anyway, I came in figuring that without any idea what the engine temps and pressure are It would be foolish to continue. And when I parked the car (I should point out that one area that improved is for the first time this year I was able to drive my car back to my paddock after every session!) smoke was coming from under the hood - shit! I toasted the engine. NO I hadn't, instead the Chinese made rubber grommets that hold the valve cover in place had turned to liquid and oil was pouring off the valve cover.

Well, I figured I should start the race and that way qualify for the Runoffs, so I did and after a couple laps came in 'cause the gauges stopped working yet again.

So I'm qualified for the Runoffs - big deal! I think the dumbest and most humiliating thing I could do is spend the -at least - $5000 to be a very distant back marker, so I've decided to give it a miss.

And that's my SCCA Majors attempt for 2017. Will there be a 2018 attempt? Yea, I think I can get this car to be competitive on the shorter tracks and I really do enjoy the fact that everyone out there on the track is doing their best to go all out - that's racing and I enjoy that part very much.

Dave Brown


Edited by dcb (08/15/17 09:17 AM)

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#14098 - 08/16/17 08:14 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 766
Loc: Greenville, SC
I never seen many with our cars have any luck with electric gauges. When Fred McConnell first built the MGB I have now, and he was driving it, he put an electric oil temp gauge in. Anyway we went to a SCCA race at Barber with the car, the electric oil temp gauge would go to over 200 degree sitting in the paddock with the car running for 2-3 minutes, I knew it was fubar, as I could lay my hand on the oil cooler and it wasn't even warm, plus most of us know good and well you can't even get a oil temp reading until with less than one lap on track. I told him to ignore the gauge, it went to 240 just driving to the grid, again the oil cooler wasn't even warm, we just ignored the damn thing, and for the next race he installed a mechanical oil temp gauge and then all was good. Another case of LED all electric sensor gauges Will Speed put in his HP Midget same thing fubar readings and the LED quit working all too soon, again he put in Autometer mech. guages and all was right with the world. Witnessing all that with these two guys never encouraged me to ever mess with what we already knew worked, which were the mechanical gauges.
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#14099 - 08/16/17 09:05 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
dcb Offline
Champion

Registered: 01/24/11
Posts: 983
Hap,

You know, I knew better when I bought them, but I had convinced myself that electronic gauges have gotten better and more reliable... at twice the price, they should be.

Just another in a long list of mistakes I've made getting this car on the track. Hopefully by next year it will be race ready and reliable.

DB

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#14100 - 08/17/17 08:23 AM Re: Dave Brown's comments on the SCCA Blackhawk Majors [Re: dcb]
Hap Waldrop Offline
Champion

Registered: 02/03/11
Posts: 766
Loc: Greenville, SC
Dave we all learn this the hard way, luckily for me, I learned it on someone's else dime. When I did the custom dash for the MGB, I was able to find every gauge I needed, either new in the box, or near new on Ebay for prices well under my wholesale pricing. I got the biggest ones they made for my old eyes, LOL smile The only guages I kept from when Fred had the car was the 5" tach which I made it to fit into the dash, and the Westech EGT dual needle gauge.

The gauges Will Speed had, the LED display gauges were sold by Pegasus Racing, they were pure junk. When I rebuilt that car, one of the first things I did was make a new dash for it with new gauges, again got killer deals off Ebay on Autometer mech gauge, which is all I sue these days. old SW gauges are good as well, if the C tubes are good on the temp gauges, all thought the new SW stuff doesn't seem to be good and VDO stuff is just cheaply made.


Edited by Hap Waldrop (08/17/17 08:30 AM)
_________________________
Hap Waldrop
Acme Speed Shop 864-370-3000
www.acmespeedshop.com
MG/Triumph Performance Street/Race Engines
The Vintage Production Car Festival
https://www.facebook.com/vintageproductioncarfestival

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