I see people recommending that cars like this should be limited to somewhere near 45 mph on the road. They often say this limit is to avoid damaging the babbitted big ends of the connecting rods. I doubt that is correct.
Chevrolets, which had three main bearings (before the 1937 models, and babbitted rods before 1953, or close, Powerglide cars) are well within my memory. I had a friend who drove Chevrolets, in particular a 1950 standard transmission model, at 80 indicated mph routinely. I had a 1949 Chevrolet which I usually drove about 70 mph. I ruined a rod, but did not throw it, after driving it wide open (indicated 90 mph on the level, more downhill and less uphill) for about 12 miles. I repowered it with a 1955 six cylinder engine, and had to more trouble before I finally sold it.
Chevrolets before the 1937 models were sometimes called "rod throwing Chevrolets," not without reason. Hudsons in the 1930s were setting speed and endurance records. They didn't do it by limiting road speed to 45 mph.
I have read stories in White Triangle News ; one in particular described the writer outrunning a Rocket Oldsmobile with a stepdown car powered by a Hudson Eight. The Short History of the Railton Car says that Hudson Motor Car Company assured them (in 1932 or 33 that the oiling system of the Terraplane 8 (read "Hudson") was "good to 5000 rpm." Railton continued to use Hudson 8 cylinder engines to the very end in 1939, when they sold out to Hudson Motor Car Company. Their advertising claimed excellent top gear performance and top speeds around 100+ mph. There is record of these speeds.
In my own case, I drove a 1934 Terraplane from South Florida to East Central Texas in June of 2013. I'm still paying for not having adjusting my own behavior to be suitable for Florida in June. I just thought I was drinking enough water. I didn't want to push the car, which I had only heard run for maybe 20 miles around town. I first limited it to 40-45 mph, then 45-50, and finally 50-60 mph. I touched 60 mph a few times. I have no doubt the engine would have done well at speeds around 70 mph, but I never tried it.
I had no trouble at all with the rotating assembly of the engine, and no particular oil consumption, either burning or leaking. Water pump. yes. Charging system, yes. I ran from the Florida panhandle to my destination in Texas on battery. Drive in daylight, get a motel before dark: charge battery at night. I bought a man-sized battery charger in Louisiana.
I am convinced that the partisans of 45 mph are merely repeating what they have heard, and the real acceptable road speed is greater than 45 mph.
I ask that persons who know come out from the shadows and tell the rest of us what they know about this. Anecdotes welcome.
Speed and endurance data too. I'm just waiting to hear some of what you can tell.
There are documented incidents of Hudsons in the late 20's/early 30's out running the law after bank robberies, hauling illegal liquor and other such nefarious activities. Granted the cops usually didn't have much more than Model A Fords - but some had other makes that were pretty fast. In the step-down era more than one Hudson six, and sometimes eights, were reworked by shade tree mechanics and used for hauling moonshine. I can testify to that personally. I was running a load of shine out of Mississippi headed for Memphis running a 40 Dodge coupe with a 1953 hemi and carrying about 50 gallons. Down around Lula, MS, on old 61 a Hudson went by me like I was standing still - I was doing about 80 or so at the time. Met up with him on Beale Street later - yeah, he was running shine and had outrun a federal agent.
Hudsonly,
Alex B
Coincidentally, I'm editing a Hudson promo movie (for a presentation I'll give this weekend), one sequence of which shows both a 1937 Hudson and 1937 Terraplane (both "splashers") being driven for 24 hours straight, full throttle, on the Bonneville Salt Flats. The Terraplane achieved an average speed of over 86 mph, including stops. The Hudson even more. I'm sure the rods must have had a bit of wear on them after this ordeal, of course. But still, it's obvious these engines were made to run at more than 45 mph!
I guess success is what you decide it to be. For a racing car, having the engine make it through the race is success. For me, I want my engine to still be alive and well after I am gone.
Years ago, I began to feel that engine speed was important for long engine life. Finally, when consulting a mechanical engineer's handbook, I found the figure 2500 feet per minute specified as the fastest metal-to -metal contact, well lubricated, that could be sustained for continuous operation.
By this time, I'd had the experience of driving three cars a lot at 60m to 65 miles per hour, and having the oil consumption of each go from better than 500 miles per quart to about 100 miles per quart. I then made calculations concerning piston speed, using the 2500 figure. When the average piston speed is 2500, the peak speed is around 3500. Too much! When the average piston speed is 1800, the peak piston speed is about 2500 feet per minute. I therefore used 1800 for my calculations.
My 2002 Honda Accord and my Pacemaker 232 engine have about the same stroke, 3.875 inches. The Accord engine reaches this piston speed at 2800 revolutions per minute, at about 75 miles per hour. The Pacemaker engine, with a 4.10 axle and overdrive, reaches 2800 rpm at about 77 miles per hour. Comparable to the Accord.
Without overdrive engaged (in 3rd gear), the Pacemaker engine reaches 2800 rpm at 54 miles per hour.
My 1935 Hudson 8 has a stroke of 4.5 inches, so it reaches 1800 feet per minute piston speed at a somewhat slower engine speed, 2400 rpm. It has a 4.10 axle, and reaches this engine speed at 49 miles per hour.
A 1947 Super 6 that I drove many miles had a stroke of 5.0 inches, so it reached 1800 feet per minute piston speed at an even slower engine speed of 2200 rpm. It also had a 4.10 axle, and reached this engine speed at 44 miles per hour.
I habitually drove the Super 6 at 50 miles per hour. As it approached 33,000 miles with me at the wheel, its oil consumption was beginning to be noticeable, although not as bad as with the three cars I mentioned at the start.
Together with Dan McNichol, I have driven the Pacemaker engine about 50,000 miles. Almost all of this has been highway miles. It still goes between oil changes (every 100 to 1200 miles) without needing oil added, and the oil pressure remains high.
Most modern cars, with automatic transmissions, provide rather low engine speeds when driving on a level Interstate highway, as indicated by the tachometer. I feel that the old cars should be driven accordingly, if the goal is to avoid running the engine somewhat above its designed criteria, and thus keeping its condition as good as possible.
Because many people want to be able to reach rather distant HET meets, putting in overdrive for the 1941 and newer Hudsons, and a different axle ratio as an alternative, as well as for the pre-overdrive cars, are nice options.
Per
Oh -O, I just saw a typo . Oil changes every 1000 to 1200 miles, (not every 100 to 1200 miles!).
Per
[b]For a racing car, having the engine make it through the race is success. For me, I want my engine to still be alive and well after I am gone.[/b] -- Per Christiansen. Not a bad thing to want.
My son is a drag racer; coincidentally, he had both his hips replaced 2 or 3 days ago. Doing fine, but it does hurt big time. He told me that when you go to the track, you go there to race. You don't say something like "We better put it back on the trailer; we might hurt it if we run." It's also true that a successful small plane landing is one you can walk away from.
Many thanks to all who shared their experience. In the middle 1950's, I worked one summer at a gas station with mechanic on duty or call 24/7. We saw lots of cars come in at night, mostly, with engines making bad noises. One Chevrolet, one Ford, one Studebaker (1937 model), uncounted Dodges and Plymouths. No Hudsons,
The Railton company used Hudson (or Terraplane) Eights from 1933 until they sold out to Hudson Motorcar Company in 1939. Railton history says that HMCC told them the Duo-Flow oiling system was "good to 5,000 rpm." The Railton was sold on claims of performance. I have read that the 1948 Hudson Super Six engines as originally conceived had the Duo-Flow system until tests proved it not up to the job.
There can be little to argue with for the calculations based on piston speed. So 45-50 mph must be at least reasonable, or perhaps a conservative estimate.. I remember reading in WTN that Pete Booz drove a 1933 Terraplane in a cross-continent caravan at about 45 mph. The car was said to have "100,000 miles" on the engine. Now that's endurance.
I just want to drive faster than 45 mph, so I will. Hope engine stays all together. Check oil frequently. Keep the memories coming.
The bottom line is, that pre-war Hudsons are low-revving engines with lots of low-end torque. They also have long strokes which (I am told) puts extra stress on the bearings. (Note that modern high speed engines have relatively short strokes; there is probably a good reason for that.)
So it would stand to reason that that either an overdrive or more advantageous rear end gearing -- or both -- would be the way to go. For example, I shoehorned an overdrive into my '37 AND kept the standard 4.11 rearend gears (even though Hudson originally used the 4.59 rearend with overdrive). The low end torque of my 3x5 engine manages pretty well, except on rather steep grades. But you can't have longevity with the original gearing in these cars because it was devised in the days when 50 mph was considered hair-raising dangerously fast!
I'm not quite smart enough to calculate piston speed, but I can see that, regardless of rotational speed, the piston passes through two dead stop locations, one near top dead center and one near bottom dead center. The locations in crankshaft degrees before or after dead center will depend on the offset left or right of main bearing centerline of the cylinder bore centers. So the length of the connecting rods is part of the real world.
Average piston speed in units of length per minute is obviously a kind of mean between the two zeros (near top and bottom dead centers), and the maximum about halfway between them I recall seeing books having the numbers needed to calculate the speeds associated with linkages.
I don't know now whether the piston-wrist pin-connecting rod-crankshaft assembly is a three-bar linkage or a four-bar linkage. But then I changed college major from Mechanical Engineering to Civil because of the Feds dangling a summer job, which never materialized, in front of me.
Other things being equal, it appears to me that a long-stroke engine will have higher (average and maximum) piston speed than a short-stroke engine, for the same rotational speed. That's why chain saws survive rotational speeds that car engines can barely imagine, and why the original Chevrolet small block engines would turn so fast.
[b]Per, would you share the method of calculating piston speed with the rest of us, particularly me? Thanks[/b].
I'd still like to hear from someone who drove a post-war Hudson with a splasher engine on the highway or in racing. How fast, my friend who holds some obscure knowledge? Thanks to you.
Robert, try this -
Piston Speed (ft/min.)
a = RPM
b = Stroke of Engine (ft)
Formula: 2 x a x b
Or do it the easy way -
http://www.csgnetwork.com/pistonspeedcalc.html
Hudsonly,
Alex B
Robert,
Alex provided the formula to relate stroke, piston speed and rpm. For example, consider an engine with a 6 inch stroke.
2 X 6 inches = 12 inches, which is 1 foot. Each revolution of this engine has a piston travel of 1 foot. Therefore 1800 feet per minute of piston travel takes place at 1800 revolutions per minute. For another engine with a stroke of only 3 inches, the engine would make two revolutions to have a piston travel of 1 foot. For this engine 1800 feet per minute of piston travel takes place at twice the revs, or 3600 revolutions per minute.
To make it easy to calculate car speed at 1800 feet per minute piston speed, I use the following formula.
32 X tire diameter (inches)
________________________ = car speed
stroke (inches) X axle ratio
For my '35 Hudson this is
32 X 28
__________ = 49 miles per hour
4.5 X 4.10
If the car has overdrive, the formula is
32 X tire diameter (inches)
_________________________________________ = car speed
stroke (inches) X axle ratio X overdrive ratio
For the Pacemaker I mentioned,
32 X 26.75
___________________ = 77 miles per hour
3.875 X 4.10 X 0.7
In this formula, the number 32 is based on my deciding to use a cruising piston speed of 1800 feet per minute. If I used 36 instead, the formula would indicate that the '35 Hudson 8 could cruise at 55 miles per hour instead of 49. That would be with a piston speed of about 2000 feet per minute. I can say that with the '35, which I used to drive on trips at 55 to 60 miles per hour, the bearings were still in excellent condition when I had to replace the pistons because their grooves had gotten very wide, resulting in oil burning.
Per
The splasher 8 was up to 1952.
Back in those days the engine oil was most of the problems. I used to drive my 36 Terraplane from Waterbury, CT to New Bedford, MA. 103 miles and at times hit 75 MPH, no overdrive, and when I sold the car it had 60 thousand miles on it and motor was never touched. Those cars were made to drive fast, but the secret was let it warm up before taking off. Walt
Thanks guys! I have a '37 six that is hung up I don't like to say frozen, that I was going to replace with something new for longer trips. Now I am going back to soaking that old engine some more and bring it back to life.
That's the ticket! The unloved engine gets a little sticky. You can bring it back to life.
[b]Rant on :[/b] It seems to me that if one is apprehensive of damage (caused by overload; how could it be anything else) to babbitted big ends of connecting rods, mean piston speed as an indicator of suitable road speed is rather a bit removed from the problem.
What about the load on the big end bearings? Doesn't it depend on speed and mean effective cylinder pressure? Isn't that closer to the believed problem of overload on the big ends?
If an engine's oil consumption jumps way up with greater than usual speed, that is more likely the result of worn out ring grooves in the pistons after long miles. Been there, done that. Old diluted oil helps.
I don't remember how fast my grandfather drove his 1936 Terraplane on the highway, but I am sure he kept up with traffic. [b]Rant off[/b]
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