How to select Hewland Gearing?

[Daryl DeArman]

Finally a simple answer to a simple question.

The OP simply asked about gearing, not a many post debate on HP and where to shift.

Actually, he asked many questions in the OP. Including, specifically: Am I understanding this right that absent a big drop off in torque curve, it is almost always better to go up to redline than to shift up?

Tony Kester used to travel around giving a driver's seminar and he said to gear a tad tall. It makes you drive the corners harder cause it sounds like you are going too slow. YMMV

I like that theory. I also like the one where you gear a bit lower than everybody else to get a better start, recover from mistakes/balked by traffic quicker. Then a bit taller on top so that you can utilize the tow off of cars in faster classes. Damn! Need more gears!!!!!

[Daryl DeArman]

Daryl...

In my first post in this thread, I said:

"The correct way to select shift points is to maximize the area beneath the power curve."

So you're not correcting me when you say that. I already understand it.

What I was correcting is your response to me stating that the shape of the curve and gear ratios are factors, to which you replied:

No. It absolutely would not. This is mathematics, and it is undeniable

Then you go on to respond to to borkracing's comment which begins with :HP being a number derived from Torque and RPM's with this gem:

Sorry, but that is completely and utterly wrong.

[BorkRacing]

Apexspeed is an incredible resource.
It is, however, on the internet. No level of expertise or knowledge is required to post ..... usually just an opinion.
Being successful in racing, is totally about the people you choose to guide you, and what guidance you choose to embrace. Now ...... that is undeniable!

And many people would rather do it their own way, than be successful.

Enjoy your project!

Listen to this guy. He helps build winning racers.

[BorkRacing]

Sorry, but that is completely and utterly wrong.

A simple thought example.

Imagine an engine with a very low torque peak at (say) 2000rpm, but where that torque only falls very slightly to the (say) 10,000rpm redline, say from 100ft-lbs to 90ft-lbs.

Now, if you can choose between being at 10,000rpm with 5:1 reduction compared to 2000rpm at 1:1 relative reduction (for the same output shaft speed:

Which will give you more output torque? The math is easy.

5:1 speed reduction means 5 * 90 = 450ft-lb torque at the output shaft.

1:1 means you get 100ft-lbs at the output shaft.

Still think HP beyond peak torque is just for bragging rights?

The power figure combines both the torque you're getting AND the amount of reduction you can apply to that torque before it gets to the wheels.

The power curve rules.

Apples to oranges. Lets compare same to same
Are we talking engine torque or torque delivered by the gearbox?
5:1 at 2000 RPM has more torque than at 10,000 RPM, as you showed gears are torque multipliers.
HP can be calculated at any gear ratio, but needs to be 1:1 when comparing car to car because of course a car in 1st gear will have more available torque than when it is in top gear.

Enjoy your arguments gentlemen. I am out of here.

Robby

[alangbaker]

Apples to oranges. Lets compare same to same
Are we talking engine torque or torque delivered by the gearbox?
5:1 at 2000 RPM has more torque than at 10,000 RPM, as you showed gears are torque multipliers.
HP can be calculated at any gear ratio, but needs to be 1:1 when comparing car to car because of course a car in 1st gear will have more available torque than when it is in top gear.

I was comparing same to same. Of course I'm talking engine torque.

At any given road speed, you will get different engine RPMs in different gears. I gave you a theoretical way of describing a situation.

You can't use 5:1 @ 2000 if you were just using 5:1 at 10,000. You have to use 1:1 if the road speed is constant.

So if you have 100ft-lb at 2000rpm at the engine, then at whatever road speed you can use a 1:1 ratio for, you MUST use a 5:1 ratio at 10,000rpm. Ergo, you get 5 times whatever torque you have at 10,000rpm delivered at the wheels. For any engine torque more than 20ft-lb, that means you'll get more torque at the wheels.

Examining the power curve just combines those two quantities into one. Since HP = torque (in ft-lb) * RPM / 5252, 100ft-lb @ 2000 rpm is...

38HP.

Do you want to take a wild stab at what 20ft-lb at 10,000 rpm would be?

[BorkRacing]

I was comparing same to same. Of course I'm talking engine torque.

At any given road speed, you will get different engine RPMs in different gears. I gave you a theoretical way of describing a situation.

Do you want to take a wild stab at what 20ft-lb at 10,000 rpm would be?

No

You are talking gearbox torque and claiming it is engine torque.
Yes, torque at the output shaft changes, at the flywheel it does not.

I am happy you have discovered math, enjoy yourself.

Once again, I am done. Find someone else to argue with. Good day

[alangbaker]

No

You are talking gearbox torque and claiming it is engine torque.

No. I'm really not. I'm talking about engine torque at one end of the system, and what the gearbox does to multiply that torque.

Yes, torque at the output shaft changes, at the flywheel it does not.

It changes at different RPMs, Robert.

Do I have to make it concrete from end to end?

I am happy you have discovered math, enjoy yourself.

Once again, I am done. Find someone else to argue with. Good day

No one forced you to come back and argue with this. Don't get all huffy.

[Jbird57]

Any suggestions for 9:31 MK8/9 GB Formula Ford? Thx

I put the chart in a spreadsheet and calculated the speed at redline (assuming 7k, 22" tires, 10/31 R&P) and then the spread of mph between redlines for the gears. It further shows how little consistency there is in that as well, and how track specific it really is.

Track	1st Gear Speed at 7k redline	2nd	3rd	4th	Gap b/w 1st and 2nd @ Redline	2nd and 3rd	3rd and 4th
Atlanta Motor Speedway	19/31 91	22/30 108	24/28 127	23/24 141	17	19	14
Blackhawk Farms Raceway	18/32 83	20/31 95	22/29 112	21/25 124	12	17	12
Brainard International Raceway	18/34 78	20/30 99	23/28 121	23/24 141	21	22	20
Carolina Motorsports Park	17/29 86	17/25 100	22/29 112	24/27 131	14	12	19
Charlotte	19/31 Same as Atlanta	22/30	24/28	23/24	17	19	14
Corpus Christi (2.8 mi. Course C)	19/33 85	20/31 95	21/27 115	24/26 136	10	20	21
Daytona International Speedway	20/30 99	22/30 108	24/28 127	23/24 141	9	19	14
Des Moines	17/34 74	19/33 85	21/30 103	23/29 117	11	18	14
Firebird International Raceway	19/33 85	21/31 103	22/29 112	24/27 131	18	9	19
Gateway International Raceway	18/32 83	20/30 98	22/28 116	24/26 136	15	18	20
Gingerman Raceway	17/33 76	19/31 91	21/30 103	22/28 116	15	12	13
Grattan Raceway	17/34 74	19/32 88	22/30 108	24/26 136	14	20	28
Hallett Motor Racing Circuit	16/35 68	18/33 80	20/30 99	23/28 121	12	19	22
Heartland Park Topeka	17/34 74	20/31 95	22/29 112	21/24 129	21	17	17
Indianapolis Raceway Park (Oval)	19/31 91	21/31 103	24/28 127	23/27 126	12	24	-1
Indianapolis Raceway Park (Road Course)	18/32 83	20/30 98	23/29 117	25/27 137	15	19	20
Lakeland	18/32 83	20/30 98	22/29 112	23/29 117	15	14	5
Lime Rock	20/30 99	21/29 107	23/29 117	24/26 136	8	10	19
Memphis Motorsports Park	17/33 76	20/33 90	22/29 112	24/26 136	14	22	24
Mid Ohio	18/33 81	20/31 95	21/29 107	21/24 129	14	12	22
Moroso	17/33 76	19/31 91	24/28 127	24/26 136	15	36	9
Mosport	18/34 78	20/30 98	22/28 116	24/27 131	20	18	15
Nelson Ledges	18/33 81	20/30 98	23/29 117	24/26 136	17	19	19
New Hampshire International Speedway	17/33 76	20/31 95	23/29 112	24/26 136	19	17	24
Phoenix (Road Course)	16/34 70	19/31 91	21/29 107	21/24 129	21	16	22
Portland International Raceway	19/31 91	21/29 107	24/28 127	24/26 136	16	20	9
Road America	18/32 83	20/30 98	23/28 121	23/24 141	15	23	20
Road Atlanta	19/32 88	21/31 103	23/28 121	23/24 141	15	18	20
Roebling Road	19/32 88	21/30 103.5	23/28 121	24/27 131	15.5	17.5	10
Sears Point	17/34 74	20/31 95	22/29 112	24/27 131	21	17	19
Sebring (Long Course)	18/34 78	20/30 98	24/28 127	24/26 136	20	29	9
Sebring (Short Course)	17/33 76	19/31 91	22/29 112	24/27 131	15	21	19
Shanonville	16/34 69	19/31 91	21/29 107	23/28 121	22	16	14
St. Petersburg	17/33 76	19/31 91	22/29 112	24/27 131	15	21	19
St. Jovite	17/35 72	19/31 91	22/30 108	24/27 131	19	17	23
Summit Point	19/33 85	20/30 98	23/29 112	24/26 136	13	14	24
Texas World Speedway (1.8 "school" config)	19/32 88	22/30 108	23/28 121	23/24 141	20	13	20
Texas World Speedway (2.9 config.)	18/33 81	20/30 98	23/29 112	24/26 136	17	14	24
Trois Rivers	17/33 76	19/32 88	21/30 103	23/28 121	12	15	18
Virginia International Raceway	18/33 81	20/30 98	22/29 112	24/26 136	17	14	24
Waterford Hills	17/34 74	19/31 91	21/31 100	22/29 112	17	9	12
Watkins Glen (Long Course)	20/30 99	21/30 103	23/28 121	24/26 136	4	18	15
Watkins Glen (Short Course)	20/32 92	21/30 103	23/28 121	24/26 136	11	18	15
Willow Springs	19/32 88	21/30 103	22/28 116	24/26 136	15	13	20

[Rick Iverson]

The proper answer to this question:

Ask knowledgeable experienced racers that are successful (and faster than you) with similar cars what ratios they use.
Use those ratios until you find a better advisor or identify a problem that can be solved by some of this engineering mumble-jumble .... or just plain common sense.

Greg, tact

[TimH]

Any suggestions for 9:31 MK8/9 GB Formula Ford? Thx

Thank you Scott Young.

[problemchild]

Greg, tact

I believe that my message is completely accurate and that an expanded version should be posted on every shop wall.

"Do what successful people do. Learn and evolve!"

[Rick Iverson]

I believe that my message is completely accurate and that an expanded version should be posted on every shop wall.

"Do what successful people do. Learn and evolve!"

Greg:

I concur completely, your message was spot on. “Lean on them, and most likely, fellow racers will share”.

In the early 70’s, there was a rag we all subscribed to in Autoweek. And a fellow racer, whom has formidable racing credentials, submitted an article on gear selection. He used a pseudo math solution that was not available at that time. So actually friend, math counts. May not be 100% accurate, but gives one a starting point.

Lastly, I spent a little time in the military, and learned quite quickly about …… conversation, both written and spoken. There is a source, a message and a receiver. And the most effective way to, persuade or mentor, is to be amicable.