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Blog

The Kurtis 500G roadster vs. The Watson roadster

Posted on September 20, 2009 at 9:18 PM

When I think of an Indy roadster, the image that comes to my mind is the Kurtis 500G and the Watson roadster.    These cars were the most produced cars of the roadster era with Kurtis building 16 of the 500G and G2 models in 1956 and 1957 and Watson building 23 of his roadsters between 1956 and 1963. Both cars were designed and built by the top pro builders and mechanics of the day.

  These cars had almost identical layouts with the driver offset to the right and the vertically mounted OFFENHAUSER engine offset to the left and large rear mounted fuel tanks . They used the same standard Halibrand driveline, running gear and suspension components, brakes, steering gear, four bar cross torsion suspension, all mounted on a steel tubular space frame. They had almost identical length, width, wheelbase and track dimensions and beautifully graceful bodywork.


BUT, there was a difference in design philosophy between these two cars that, ultimately, led to great success for one and mediocrity for the other.


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 The Frank Kurtis KK500G roadster

  Frank Kurtis had built approx. 30 roadsters between 1952 and 1955. For 1956, he brought out the low and sleek 500G model.

  It featured stout structural design and construction with beautiful "all business" aluminum bodywork.    Variations of the 500G included, three of the sixteen being built as "left side driver / right side engine" cars.  The 500G raced, at Indy, from 1956 to 1962, scoring one pole position and no wins. It was not much more successful anywhere else.

 Top teams using the Kurtis 500G were Bowes Seal Fast, Sumar and Bardahl.




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 The A.J. Watson roadster

  A.J. Watson won Indy in 1955, as chief mechanic on the John Zink Kurtis 500D. He had bought that car as a kit and assembled it with his own ideas.

  For '56, A.J. took his experience with the 500D and built his own Indy roadster. Based on the 500D style space frame, A.J. built a lightweight chassis, eliminating some of, what he considered, needless bracketry & structure and he simplified & lightened the steering system. He also used a lot of magnesium for body panels and bulkheads. A.J. finished his new car off with stylish, Larry Shinoda designed, bodywork.

  A.J. continued to build and develope this same car until 1963. He was one of the first to use light weight fiberglass tails and noses.

  The only noticeable change in these cars was, following the 1958 season, when they came up with the famous "shark nose".

  In addition to the 23 roadsters that Watson built, there were, probably, another 6 or 8 Watson clones built by other builders of the day, including Ewing and Trevis. In fact , the 1961 winning car was a Trevis built Watson clone.

  The Watson roadsters raced at Indy from 1956 through1966, scoring six poles and seven wins. They also had great success at other events on the champ car trail.

  Top teams using Watson roadsters included Leader Cards, John Zink, Sheraton-Thompson, Dean Van Lines and Agajanian.




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   Both the Watson and the Kurtis 500G were defeated at indy in '57 and '58 by the clever Salih-Belond "laydown" roadster.

  For 1958, Kurtis abandoned the 500G and his next two cars used "laydown" engines. Also several of the original 500G cars were converted to "laydown" engine configuration.

  Watson didn't fall for the "laydown" engine fad. He stayed true to the upright engine layout and was rewarded with five "500" wins from '59 through '64, plus the 1961 "500" win by a Trevis built Watson clone.

 Watson never built a "laydown" car and none of his roadsters were ever modified to use a "laydown" engine.


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Comparing the spectacular success of the Watson roadsters and the relative failure of the Kurtis 500G roadsters comes down to a few simple things..


weight & complexity- The Kurtis 500G was a very stout car with too heavy brackets, too heavy braces and too heavy parts. A.J. reduced everything, he could, down to its simplest possible form and used the lightest possible materials. This resulted in a weight advantage of around 250 lbs. This made for better acceleration, better braking, less tire wear and less driver wear.

  A 250 lb weight difference was just too much for the 500G to overcome.


suspension geometry- Site member, Steve Miller, pointed out, in his "comment", that Watson had a "track bar" setup that created superior left rear tire "bite".  Another guy pointed out to me that the radius rod angles on the 500G caused a rear roll steer condition.  A driver, who drove both cars, said that the 500G was a "handful" and very tiring to drive, compared to the Watson.

   Either by design or by happenstance, the Watson had better suspension geometry.

    


horsepower & setup- While both, Frank Kurtis and A.J. Watson, were great designer/builders, A.J. was also a chief mechanic and engine builder. His "in the pits", hands on experience with setups, as well as his ability as an engine builder and innovator, were major factors in the success of his cars.

  Bottom line is "power to weight" ratio......  Advantage to Watson.


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  My personal favorite????

 I like the Kurtis 500G... particularly, the Bardahl "left hander".





mac miller in INDY

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7 Comments

Reply Ed Tebbenhoff
1:01 PM on September 24, 2009 
Dear Mac,
I really enjoy you blog, your contributions to Trackforum and your wonderful cars. I go to Milwaukee every year. We've never talked but I've been for four years now (always wearing a floppy hat and a Mate's White Front tee shirt). Two questions: why do you prefer the 500G? Is this a based on beautiful lines? On craftsmanship? As you've indicated, it can't be based on a great record of success. But I too, really like these particular cars; they have an edgy look, like they mean business in a way that a Watson doesn't. 62 or 63 Novi's have the same look of pure aggression. Maybe its just Kurtis. Watson's are certainly gorgeous cars but they are more polished and less brutal looking, at least to me. So here is a curiosity: how about Jim McElreath's Schultz Fueling Equipment car in 1962, a 500G with Watson body work. Do you know anything about how and why that happened?
Reply Ed Tebbenhoff
1:06 PM on September 24, 2009 
I was just thinking that maybe I misspoke in my previous post. I don't have pictures in front of me but wasn't the Schultz car really a Kurtis chassis, tail and cockpit/engine cover with a Watson nose piece?.
Reply Steve Miler
11:22 PM on September 25, 2009 
Mac,
Your comparisons of the Watson and Kurtis chassis is right on, however, there is another mitigating factor. Kurtis used a compression panhard rod in the front and a jacobs on the right rear, usually a good way of loading the right side tires. Watson used a tension panhard mounted low in the front and a jacobs link on the left rear. The jacobs link will tend to load the side it's connected to, so the Watsons got a much better bite off the left rear. Currently I am restoring a Kuzma that was built in 1958 for Agajanian that Ruttman drove and it is as light or lighter than the Watsons, but it has the Kurtis method of lateral links and it handled like crap. Two years later Aggie had enough and traded it in for Calhoun. Watson changed the linkage, stuck in a borrowed engine and put it in the show with Bill Homier driving. Aggie spent a fortune and made tons of changes to the car and never made a race at Indy with it. However, the roadster builder with the best understanding of handling I believe had to be Lesovsky. I restored the Johnny Thompson car from 1959 and 60 a couple of years ago and I was just amazed the more I got into it how geometrically correct it was.
Steve Miller
Reply ★ Owner
7:53 AM on September 26, 2009 
Hi Ed,
First, Welcome and thanks for joining the website!
I love all of the roadsters but, like you, I just like the "no nonsense" look of the 500G. The dark colors of the navy blue Sumar and the black Bardahl had a very sinister look. I hate race cars that look like they are smiling.
As I said, The Watson body work was designed by Ford company stylist, Larry Shinoda, and I know that "stylists" have a tendency to get too "stylish".
HA!
Of course, the Watson "shark nose" was one of the most popular and identifiable shapes ever to appear at the Speedway.
The Schultz Fueling car was a Kurtis with a Watson style nose. the rest of the body was Kurtis. The only info I have is that the car was wrecked in 1960 and returned in '61, rebuilt, with the "Watson" nose.... apparently , owner, Ollie Prather preferred the "Watson" nose.
I have seen you at Milwaukee with the "White Front" tee shirt.. I have had a few beers at the White Front. The place is now a "gentleman's club". HA!

Thanks for your comments! questions answers and comments are always welcome.
Reply mac miller
9:20 AM on September 26, 2009 
Steve Miler says...
Mac,
Your comparisons of the Watson and Kurtis chassis is right on, however, there is another mitigating factor. Kurtis used a compression panhard rod in the front and a jacobs on the right rear, usually a good way of loading the right side tires. Watson used a tension panhard mounted low in the front and a jacobs link on the left rear. The jacobs link will tend to load the side it's connected to, so the Watsons got a much better bite off the left rear. Currently I am restoring a Kuzma that was built in 1958 for Agajanian that Ruttman drove and it is as light or lighter than the Watsons, but it has the Kurtis method of lateral links and it handled like crap. Two years later Aggie had enough and traded it in for Calhoun. Watson changed the linkage, stuck in a borrowed engine and put it in the show with Bill Homier driving. Aggie spent a fortune and made tons of changes to the car and never made a race at Indy with it. However, the roadster builder with the best understanding of handling I believe had to be Lesovsky. I restored the Johnny Thompson car from 1959 and 60 a couple of years ago and I was just amazed the more I got into it how geometrically correct it was.
Steve Miller


Hi Steve,
Great comments! and a great addition to this blog subject. Isn't it interesting how these guys used basically the same pieces but arranged them differently with much different results????
Another visual difference was the low mounted front torsion bars on the Kurtis compared to the high mounted bars on the Watson.
Wouldn't be interesting to subject these cars to the same design and testing used today with CAD, CFD, the seven post rig and wind tunnel??? On the "calhoun", I built, I made many minor changes to the geometry according to the animation, I ran on my computer.
Thanks again for your insight and comments.......... Keep them coming.
mac miller
Reply ★ Owner
7:19 AM on October 2, 2009 
mac miller says...
The Schultz Fueling car was a Kurtis with a Watson style nose. the rest of the body was Kurtis. The only info I have is that the car was wrecked in 1960 and returned in '61, rebuilt, with the "Watson" nose....


Ed,
I have had a closer look at this Schultz car and there was more changes for 1961 than just the nose. When the car was rebuilt, the torsion bars were moved from below the front axle center to above the front axle center, like the Watson.
Maybe this suspension modification is the main reason that they went to the Watson nose.....???????
mac miller in INDY
Reply Sam d
12:24 PM on January 13, 2019 
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