Community Shop Talk

Torque Troubles...

Online Engine Conversations from SmokStak and the Stationary Engine List

SmokStak

The following thread comes from a recent topic on SmokStak. (www.enginads.com smokstak.cgi). SmokStak is an online bulletin board discussion group where old-iron collectors converge in cyberspace to discuss all things related to stationary engines. Various individuals from around the world started, commented and concluded the following remarks.

I'm curious to see if anyone knows the foot-pounds of torque an old engine puts out compared to modern-day engines. What would a 225 HP Fairbanks-Morse Y put out compared to a modern-day 225 HP V8 or any two engines of the same horsepower? Has anyone ever hooked up an old engine to a dynamometer? - Tanner

Power equals torque times the rpm. For engines with the same horsepower at the same rpm, torque must equal the same. Advertised horsepower means nothing unless you specify the rpm. - Brent

I'm guessing, but I think the torque equals the same amount as any other engine of the same horsepower. Then again, those heavy flywheels will carry a lot of torque once they get spinning.

The thing to remember is the old engine produced horsepower at a low rpm. If they could stay together at 2,000 rpm, they would produce a lot more horsepower. - Vernon

I don't see how that can be possible. Look at the rpm a modern-day 6 HP engine has to run to equal the same horsepower as my 6 HP 1925 Fairbanks-Morse. If you turn the rpm down to match my FM, I don't think you're going to get the same torque.

I always thought torque was generated by an old engine's massive flywheels, and torque in modern engines is generated by high rpm. I don't see how the two can be compared by saying equal horsepower and rpm must equal the same torque. - David

The 'flywheel effect' is inertia. Newton stated that an object in motion tends to stay in motion unless acted on by an outside force (in this case friction). Inertia is the energy the flywheels impart to the system after being acted on by the torque and acceleration of the crankshaft.

I'll use my 13 HP Allis-Chalmers B as a V8 engine comparison. Put a modern 16 HP Briggs, Honda, Kohler, etc., in place of the AC, and let's see if it'll pull a 14-inch single-bottom -or better yet - a 12-inch two-bottom plow. Given the same ground speed of my B versus a Sears garden tractor, if my engine rpm is the same and gear reduction the same I'll have the same ground speed (gear reduction accounts for tire size difference).

If my gear reductions are the same, my torque multiplication to the ground is the same. Does the Sears have enough ground torque to plow like the Allis-Chalmers B? I don't think so. Old gas engines are torque monsters. They produce relatively low horsepower but a lot of torque. - John

This problem was as simple as plugging the numbers into the formula: HP = k x torque x rpm.

To get equal horsepower from an engine that's running at half the rpm, the torque must be double. To get equal horsepower from an engine that is running at 250 rpm, its torque must be 10 times that as an engine running at 2,500 rpm. - Orrin

Two engines of equal horsepower at equal rpm produce the same torque. As somebody else said, HP = k x torque x rpm. If you input a constant horsepower, rpm and constant k, then you have no way for the equation to come out other than with equal torque. - C. J.

I disagree with the theory that huge flywheels 'give' these old engines torque. The flywheel  only stores and releases the power from the combustion in the cylinder. This is easily proven by observing how long the flywheels have 'torque' if the engine is not firing. I think we know the answer to that one! - Larry

We can't forget there are different ways to measure horsepower. Modern small engines are rated at the maximum horsepower at a rated speed. Old tractor engines were rated at belt or PTO horsepower, which accounts for transmission frictional losses, etc. In a way, comparing a 13 HP antique tractor to a 13 HP Honda engine is like comparing apples to oranges. The ratings are considered in two totally different ways. I would personally take the tractor. - C. J.

If you put those huge flywheels on the same engine, it would not be off and running with a few pops of the exhaust. Rather, it would probably take 15 to 20 power impulses to get the engine up to speed. Where did all that energy go? Into the flywheels - a  very efficient place to store energy for short intervals. The only things you've accomplished are lengthening both the start-up and shutdown times, nothing more.

There's only so much power in each gasoline explosion and nothing can change that. It'll pull you through a tough spot, but the energy used at that time will have to be replaced. - Craig

I believe you can call all horsepower/torque ratios relative. Consider this: We have a 1915 Economy engine with a Webster magneto. The factory-rated horsepower is 12. Let's say we decide those flywheels are too darn light, so we hire a foundry to cast identical-diameter flywheels but with a face width of 7 inches. Go ahead and crank it up now that we've added several hundred pounds to the flywheel and run it at the same factory-rated speed of 300 rpm.

This engine isn't creating any more energy now than it was before, but I promise the measurable torque and force/resistance required to stop those flywheels, which would make any oil field engine collector envious, would be far more than a stock 12 HP Economy engine.

The critical difference between these two engines is the amount of stored kinetic energy. I'm no mathematician, but I believe when comparing an old hit-and-miss engine to a modern engine of equal horsepower that the stored energy of the flywheels is a determining factor that proves our old engines have far greater torque than their modern counterparts.

How do you measure this stored kinetic energy? I don't know, but it factors into any comparison between the two very different torque ratios. - Keith

SmokStak (www.enginads.com/ smokstak.cgi) is an engine conversation bulletin board with over 50,000 messages on file and is part of the Old Engine series of Web sites that started in 1995 as 'Harry's Old Engine.' Harry Matthews is a retired electronic engineer and gas engine collector from Oswego, N.Y., now residing in Sarasota, Fla.

... and Valve Guides

Stationary Engine List

By Helen French

The following thread comes from a recent topic on the Stationary Engine Mailing List (www.atis.net). SEL is an online bulletin board discussion group where old-iron collectors converge in cyberspace to discuss all things related to stationary engines. Various individuals from around the world started, commented and concluded the following remarks.

December tends to be a quiet month for major engine restoration projects. During the down time, however, the Stationary Engine Mailing List is preoccupied with two events: our annual online charity auction and the annual worldwide crank-up on New Year's Eve. The auction is loosely connected with engines and generally raises about \$2,500 for various charities, depending on the rivalry between the engine and tractor lists hosted by ATIS, the Antique Tractor Internet Service.

The crank-up is held in memory of past engine friends. The first new year report usually comes from Sydney, Australia, where enthusiasts run their engines before the fireworks over Sydney Harbor Bridge have ended.

In deference to our neighbors, we don't run our engines at midnight. Instead, we have an all-day party on New Year's Day, dragging out and running a selection of old engines. I'm delighted to report this year's New Year's engines included a flawless performance from Tillie, the Tillinghast half-breed oil field engine. Finally, we get the news from collectors coast to coast in America about how their engines have run on New Year's Eve, as well.

A quick glance at my collection of previous articles shows that the subject of valve guides has been sorely neglected, so I'll take the opportunity this month to fix that.

At what point should one install valve guides? My 5 HP Galloway saw rig is coming apart nicely. It has big, massive valves  not pitted and in pretty good shape - but there's a lot of radial play in the OEM guides. I'd say the Galloway has 7/16-inch stems, both worn about the same amount. I can only imagine the size of the massive valves in the 'Sweet 16.' Whew!

The Galloway valves are huge. Not so much the valve diameter, but they've got to be 1/2-inch thick! That coupled with the 7/16-inch valve stems is pretty impressive - and it's a two-piece valve. The stem is peened onto the valve. I don't care too much for valve guides, so maybe knurling is the way to go?

I don't think much of knurling. It greatly reduces the contact area and will probably wear very poorly. Why not just bore out the head and press new guides in, then do whatever is needed to the valves? Do it right and do it once.

Knurling valve guides consists of running a roller-equipped device through the guides - it creates a 'spiral groove' and displaces material, effectively reducing the guide hole's size.

I worked with a complete set of 'knurlers,' pilots and all. It took a heavy-duty drill to run through an automotive head.

This works in cars because the knurling was well-lubricated with the automotive system, but I'm not sure how it would fare with old engines like we have. The knurling held oil and actually improved efficiency. It reduces oil consumption past the valve guides if done properly.

I'd ream it out and put in new guides. I used to do that a lot, as well, and never had a lick of trouble. Those that did, well, it's typically due to a poorly done job.

If the guides are unevenly worn - or egg-shaped - knurling isn't the best answer, you'd be better to fit it with new guides. Another advantage of going with replacement guides is you put the thing back to proper specifications and can use standard or stock parts.

If you're striving for perfection, keep in mind that your valve stems are going to be worn as well as your guides. Going to extreme measures to make the guides perfect is a waste unless you repair the valves.

There's no reason hesitating to bush the guides. You could probably buy a couple reamers and the guides and do it yourself for cheaper than it would cost to hire a machinist. I've done some pretty close work using a reamer in a drill press. I always turned the drill press over by hand because the motor drives it too fast.

I have done this plenty of times, and it was always the hot ticket. Removable stems are the key, otherwise you have to make a complete new valve, which is still possible. I've gotten away without having to put guides in anything so far, but they get rustier every year!

Valves of the size needed for that 5 HP Galloway can be  purchased very inexpensively. Others (for a 1-1/2 HP Hercules, for example) can be obtained for nothing from most machine shops. Just ask them for a used valve from a 1987 Toyota. It simply needs an inch or so cut off the stem and the valve face lapped in!

It's worth looking at cast iron or phosphor bronze guides to do it right, bearing in mind that any leakage past the inlet guide and stem will affect carburetion.

It's also worth getting an engine shop to do that bit, as drilling into an oval hole could mean all sorts of alignment problems later.

I just had to make new valve spring 'towers' on a 3 HP M head. They were broken off, and the valve holes were oval like eggs. I made new valve guides and spring 'towers' in one. Boring, milling and tapping the threads, I did it in one try per stem hole. I aligned the whole setup with the help of a center hole I made in the valve head, that way I was always in the middle of the 'groove.'

In the future, I will bore the final stem hole and use a long reamer for the exact measurement. Finally, I'll mill off the top with the wrench slot. I thought this was the only way to save this head.

As usual, the List came up with several ways to achieve the same result, depending on the initial damage, level of machinist skill, and tools and material available. With warmer weather just around the corner, it's time to get the winter projects completed and ready for a new show season!

Engine enthusiast Helen French lives in Leicester, England. Contact her via e-mail at: Helen@insulate.co.uk You can join the Stationary Engine List on the Internet at: www.atis.net

'If my gear reductions are the same, my torque multiplication to the ground is the same. Does the Sears have enough ground torque to plow like the Allis-Chalmers B? I don't think so. Old gas engines are torque monsters. They produce relatively low horsepower but a lot of torque.' John

'Valves of the size needed for that 5 HP Galloway can be purchased very inexpensively. Others (for a 1-1/2 HP Hercules, for example) can be obtained for nothing from most machine shops. Just ask them for a used valve from a 1987 Toyota. It simply needs an inch or so cut off the stem and the valve face lapped in!'