Wildguzzi.com
General Category => General Discussion => Topic started by: Rough Edge racing on January 29, 2020, 08:35:42 AM
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Just what you need to set you apart from the other Harleys...
https://www.ebay.com/itm/1939-Harley-Davidson-OHV-Experimental-Prototype/283750722336?hash=item4210dc6b20:g:8VcAAOSwOI5dOGCQ (https://www.ebay.com/itm/1939-Harley-Davidson-OHV-Experimental-Prototype/283750722336?hash=item4210dc6b20:g:8VcAAOSwOI5dOGCQ)
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This looks really cool, and quite a piece of history.
I'm a little confused, though, since it is described as a "knucklehead prototype", and the fairly extensive write-up on it seems to claim it's Harley's fisrt OHV attempt, on the 45 base to save money from developing a whole new OHV engine. But it is listed as a 1939 motorcycle, and described consistently with that, yet the knucklehead big twin came out in 1937, and the write-up of the history of this bike, and how it relates to H-D development, doesn't mention that anywhere.
PhilB
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The provided write-up is confusing if you're not into these engines.
Short version is the new large displacement overhead valve (Knucklehead, released in 1936) engine had a completely revised crankcase with a single camshaft while the concurrently offered flathead (UL large displacement or WL smaller 45 cu displacement) bottom end utilized four individual cam shafts. This bike uses the 4 camshaft timing chest with two pairs of parallel pushrods vs all four pushrods converging from a single camshaft. The four individual camshaft allow much greater and more economical tuning capacity. Coupled with better pushrod geometry, this lower end configuration was the preferred platform for the majority of HD racing.
Ultimately, the four camshaft timing chest survived when the engine & transmission were unitized for the K series (still flathead) and then became OHV with the Sportster in 1957. All the factory WR, KR and XR race-spec bikes are four cam timing chests. The OHV single cam big twin (1936-1999/2000 knucklehead,panhead, shovelhead, Evo) is a different machine.
With the four cam lower end and full aluminum top end, this is a very cool machine. HD didn't offer an aluminum top end on anything until the release of the revised alloy XR750 in 1972, which again utilizes a four cam timing chest.
Edit- probably should add that the lower end of the original 1936 OHV Knucklehead with single camshaft had many similarities to various earlier models, but none of these incorporated all the new features of the Knuckelhead.
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The provided write-up is confusing if you're not into these engines.
Short version is the new large displacement overhead valve (Knucklehead, released in 1936) engine had a completely revised crankcase with a single camshaft while the concurrently offered flathead (UL large displacement or WL smaller 45 cu displacement) bottom end utilized four individual cam shafts. This bike uses the 4 camshaft timing chest with two pairs of parallel pushrods vs all four pushrods converging from a single camshaft. The four individual camshaft allow much greater and more economical tuning capacity. Coupled with better pushrod geometry, this lower end configuration was the preferred platform for the majority of HD racing.
Ultimately, the four camshaft timing chest survived when the engine & transmission were unitized for the K series (still flathead) and then became OHV with the Sportster in 1957. All the factory WR, KR and XR race-spec bikes are four cam timing chests. The OHV single cam big twin (1936-1999/2000 knucklehead,panhead, shovelhead, Evo) is a different machine.
With the four cam lower end and full aluminum top end, this is a very cool machine. HD didn't offer an aluminum top end on anything until the release of the revised alloy XR750 in 1972, which again utilizes a four cam timing chest.
Edit- probably should add that the lower end of the original 1936 OHV Knucklehead with single camshaft had many similarities to various earlier models, but none of these incorporated all the new features of the Knuckelhead.
Thanks for schooling me Cliffrod. I had no idea the old HD racing iron had 4 cams.
Very interesting.
Rick.
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The provided write-up is confusing if you're not into these engines. ...
Thank you.
PhilB
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Sounds like Prototype Manure spreading going on here
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There are a few guys adapting iron Sportster heads to the old 45 side valve engine.. Sorta what Harley did in the 1950's . I believe it's called a "Magunum 45"... I think the 45 side valve engine came out around 1937 ...
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This specific bike, or at least the write up, may be bs as Mike suggests. I don't know. Reading what the journalist-proofreader/spellchecker-editor process does to a valid technically/historical article often leaves a lot to be desired. That doesn't even include what happens when the lines between fact & fiction get blurry. There's so much garbage written about HD in general that many books and articles are worthless.
To me, if it's a real HD prototype effort, it makes complete sense as a predecessor of the eventual OHV Sportster engines. Having that mentioned in the write-up would clarify a lot, even if such a claim was only obvious in hindsight long after the original effort. The Big Twin Knucklehead OHV of 1936 was a good move for HD, so having their smaller model similarly updated to OHV seems practical to pursue. If this bike is real, that's basically what they did.
Faking both aluminum heads and aluminum cylinders would be more than a casual effort. Aside from the alloy XR in 1972, other aluminum top end parts for Sportsters or Big Twins didn't enter production until the Evolution series around 1985. If there are aluminum parts under that black paint, those parts on that bike look very different than any of the later pieces.
If factual, timing of the effort seems relevant. Within a year or two of 1939, everything civilian became less important than addressing WWII. The 45 ci (750cc) vs 30.50 (500cc) details in the article sounds curiously reminiscent of the story of HD's WL/WA vs Indian's 30.50 & the US Army war contracts. So many HD fables get tangled into factual accounts. This might be happening again here.
Post war, the completely new unitized K-series flathead engine was on the road by 1952 which would mean it had to be in R&D soon after the war ended. This would be the rational direction towards modern technology compared to using the old tech W pre-unit bottom end configuration. The WL flathead 45 stayed in production for the Servicar into the early 70's, but that's another topic.
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There were and are a lot of talented people capable of casting cylinders and heads from aluminium , unless some documentation exists to prove what this thing is some factory prototype , I am also skeptical .
Dusty
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Here is a picture of one I took at a recent 100 year reunion of the WSPD motor officer reunited. I think it was supposed to be in 1936- 1938 timeline.
(https://i.ibb.co/2dc7888/13529-A9-D-73-CB-476-F-BC42-45-A4-C4-EB1-E3-D.jpg) (https://ibb.co/2dc7888)
porsche cayenne 0 60 mph (https://statewideinventory.org/porsche-0-60-times)
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There were and are a lot of talented people capable of casting cylinders and heads from aluminium .
Dusty
Doing the accurate 3D work isn't the issue. Paying for it is normally the hard part.
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The Harley 45 engine came out in 1929 I think, it finally got a pressure oil system in 1937. DonG
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Doing the accurate 3D work isn't the issue. Paying for it is normally the hard part.
Meh , have you ever heard of Burt Munro ?
Dusty
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Meh , have you ever heard of Burt Munro ?
Dusty
All you need is a shed and a lemon tree...
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The aution ended..... But check out the casting symbol on this circa 1970 Routt 750 cylinder for a 650 Triumph....I have a Routt cylinder
(https://triumphbonneville120.co.uk/resources/scan0005.jpg.opt888x597o0%2C0s888x597.jpg)
Now look closely at the casting symbol on the experimental Harley head...They look the same? cast at the same foundry? And when?
(https://i.ebayimg.com/images/g/95IAAOSwcENdOGDE/s-l500.jpg)
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Meh , have you ever heard of Burt Munro ?
Dusty
Several years ago I was asked to make a wax model of his World Fastest Indian to cast for a local AMCA Chapter's annual Legend of the Year trophy, I said that's bogus to the memory of Burt Munro. So I carved the streamliner model from a Ford Truck axle, just like Burt reportedly carved his connecting rods from a Ford truck axle after 50 OEM rods failed. The scale and proportions of this one matched the movie machine more closely than the actual bike to better fit on the trophy, which also features a bronze art casting of Burt's original carved-from-a-truck-axle rods. Posted pics here about it in 2018 https://wildguzzi.com/forum/index.php?topic=96282.330 (https://wildguzzi.com/forum/index.php?topic=96282.330) but here they are again
(https://i.ibb.co/zfGdsK1/DSC-0396-lr1.jpg) (https://ibb.co/zfGdsK1)
(https://i.ibb.co/NTbLLDd/DSC-0397-lr1.jpg) (https://ibb.co/NTbLLDd)
(https://i.ibb.co/Nxp7xzD/DSC-0400-lr1.jpg) (https://ibb.co/Nxp7xzD)
(https://i.ibb.co/7pdXDNC/DSC-0402lr1.jpg) (https://ibb.co/7pdXDNC)
There's a huge difference between simple backyard gravity casting aluminum pistons to then machine into usable condition vs pressure casting all those fins & thin cross sections to ensure a complete investment and limit porosity. It obviously can be done because it was done by someone. Who or when that was, I have no idea. But somebody paid.
Now it's back down to the studio to carve another bunch of daffodils in granite, like this one I shipped yesterday. First I'll step past my ugly-on-purpose (to match a missing original for a restoration project) 30" long bronze peach leaf that's here in the office, waiting to be installed-
(https://i.ibb.co/gg2t0tL/Daffodils-DSC-2931-crop1.jpg) (https://ibb.co/gg2t0tL)
(https://i.ibb.co/j8vJTQw/IMG-7158.jpg) (https://ibb.co/j8vJTQw)
Eventually, I'll find spare time around studio work to do more on my V700 Corsa Record ...