42 replies to this topic

[Steve Okeefe]

Philippe,

 

Would you agree that race-winning cars win at least in part because they are, amongst their competitors, best optimized for the track conditions existing on race day?

 

The point being that track conditions drive the design and tuning of race-winning cars to a greater degree than most people (outside of top-level builders and drivers) realize. Mike Morrissey and the Russkit crew discovered this in a big way at The Groove raceway in Royal Oak, Michigan in 1965.

[tjallen]

If you take a look at Fred Rannalli's US Patent Application 3195472, filed June 5, 1964, he claims to be the inventor of the drop arm.

 

The Google Patents scan and OCR of this patent ( https://patents.goog...atent/US3195472 ) are very poor, so I have uploaded a pdf of the patent, available from the US Patent Office, including diagrams, and you can read it yourself.

 

http://gywh.com/slot...nali-patent.pdf

 

Of additional interest is the complex engineering explanation Rannalli gives for the function of the drop arm. His explanation is complete with physics principles and scientific equations. I'm a philosopher, not an engineer! But the engineers may enjoy it.

 

I will summarize some of the patent application here.

 

First, his claim of the invention:

 

Claims (1)

1. IN A SLOT CAR RACER OF THE TYPE DESIGNED TO BE GUIDED ALONG A TRACK BY A LONGITUDINAL SLOT FORMED IN THE ROADBED THEREOF AND HAVING AN ELECTRIC MOTOR ENERGIZED BY A SOURCE OF POWER ASSOCIATED WITH THE ROADBED, THE IMPROVEMENT IN THE SLOT GUIDE SUSPENSION MEANS COMPRISING, A SLOT GUIDE ARM HAVING A SLOT GUIDE DEPENDING FROM ONE END, MEANS CONNECTING THE OTHER END OF SAID ARM TO THE FRAME OF THE CAR SO THAT THE MOVEMENT OF SAID ARM IS SUBSTANTIALLY RESTRICTED TO A VERTICAL PLANE AND SAID SLOT GUIDE IS DISPOSED TOWARD THE FRONT OF THE CAR, AND MEANS URGING SAID SLOT GUIDE AND ARM DOWNWARDLY TOWARD THE TRACK WHEREBY THE SLOT GUIDE RIDES INTERIOR OF THE SLOT IN THE ROADBED AS THE CAR MOVES THEREOVER.

 

The claim is restated and the drop arm is re-described several times:

 

"The present invention constitutes a breakthrough in slot guide suspension systems....."

 

"The present invention utilizes a slot guide arm pivotally mounted towards the rear of the frame of a slot car so that the front of the car and the arm can move in vertical directions relatively independently of each other. The forward end of the arm is also weighted so that the slot guide carried thereon remains in the slot as the racer moves over the track."

 

He also admits there are already examples being tested:

"Tests of racers utilizing the principle of this invention have shown...."

 

Several paragraphs later, he begins to explain how the drop arm works:

"While it is not certain just why the present invention realizes such a substantial improvement in slot car racer performance and, even though the reason for the superior performance is really immaterial, the following tentative explanation is offered:"

 

The explanation seems to make sense, he goes on for several paragraphs, but then the explanation goes way over my head! You engineers may enjoy this part:

 

 

 

Summary: this patent claiming invention of the drop arm, should be considered and weighed along with lots of other evidence. Yes, I have seen photos of drop arms long before this patent application date of June 1964. So, what are we to make of this?

[don.siegel]

Interesting Jim - just looks like Fred R was the first to think about filing for a patent - wonder if it was ever granted, given all the previous instances of use! 

 

Here's the earliest reference I could find, in fact by three guys claiming to have invented the drop arm, for road cars: from Car Craft, February 1962... 

 

Don 

 

 

[

/URL]

 

and a bonus, just because it was on the same page... from Model Car Science, August 1963, still well ahead of Mr. Rannalli. 

 

[URL=http://s56.photobucket.com/user/dgersh/media/Print/DroparmguidesMCS863.jpg.html]

[Ecurie Martini]

Disclaimer: I am not a patent attorney - but I have a number of patents filed and awarded. I have also been called upon as an expert witness in cases both supporting and attacking issued patents.  

 

My take? The Ranalli patent, if issued, would have been easily attacked on the basis of prior art.
 
EM

[tjallen]

Rannalli's patent application was granted on July 20, 1965 (just over a year after filing).
 
Also named is James B. Gambrell, a Texas patent attorney and intellectual property lawyer, who passed away in 2010. (Linkedin profile of Gambrell HERE ). Gambrell was a partner with Fowler, Knobbe & Gambrell (patents and copyrights experts) from 1963 to 1966. Fred Rannalli assigned the patent to Gambrell. One would expect that Gambrell licensed the rights to others, and challenged those who violated the patent, though I have no further information on any licenses or challenges.

[Steve Okeefe]

Wow...

 

Just wow...

 

Perhaps Fred Rannalli was hoping he had a tiger by the tail.  In reality what he had by the tail was a sizable white elephant.

 

[TSR]

The drop arm was invented by Voytek Dolinski in 1962 and first applied on a drag racing car.
 
Because of "previous art," Rannalli could only obtain a "design" patent, not a "basic" patent. In other words his patent would never have stood scrutiny if contested. But no one contested it...
 
In fact, why bother? Was Rannalli going to spend good money to defend a concept already used by thousands by the time he patented it?

[Steve Okeefe]

The first sentence in the "Mixing Rod Special" article attached to post 28 mentions a Voytek Dolinski as one of the developers of the "Swinging Arm" pickup system (thank you, Don Siegel).

 

Could this be Voytek Dolinski... the (obscure) actor?

 

Credits:

The Village (movie) - 1953

Goodyear Playhouse (TV series) - 1954

Armstrong Circle Theatre (TV series) - 1956

Playhouse 90 (TV series) - 1959

The Blue Angel (movie) - 1959

 

No photos, no bios, and he disappears after 1959.

 

Same guy? There are after all, just so many people with that name...

[TSR]

Well, why not? Would be fun stuff if the same guy! Many stars and business people were active in the slot car world then...

[don.siegel]

You know, I think I was in contact with Voytek a few years ago... will have to go back through all my emails! 

 

Don 

[zipper]

Btw, speaking of actors did remind of Dan Blocker, "Hoss of Bonanza", a slot car enthusiast https://books.google... racing&f=false ...and Dan Glimne, Swedish slot racer did copy some of those Popular Science pics into his book "How to race Miniracing" - I wonder if he got the rights to publish the pics....

[Steve Okeefe]

You know, I think I was in contact with Voytek a few years ago... will have to go back through all my emails! 

 

Don 

 

Please do!  It would be another piece of the puzzle fitted into place.  Voytek Dolinski - whoda thunk? 

[A. J. Hoyt]

When I was very young (prior to becoming an engineer), I had always thought the Drop Arm was to permit a "conformance" to the braid/slot while the chassis proper was allowed to buck, roll and heave to the track surface so it makes sense that they may have tended to "delay" the guide coming out of the slot, preventing a catastrophic "launch" and crash.

 

Isn't that what most components (like hinged Bat Pans) do (did) on "good handling" slot cars? They tend to delay the disengagement of the guide flag due to roll (Bat Pans rise in corners) or track surface humps (everywhere) by providing the Drop Arm and Bat Pans a "place to go" until the corner is over or he hump is passed (until it can't) to prevent a de-slot and then settle back down afterwards. Didn't "good handling" just mean that the car was tolerant (forgiving) instilling a confidence to the racer to just concentrate on going faster?

 

Now an engineer, I can't describe it any better than that. I think that it was a mass - pendulum frequency thing that could be tuned to match the track conditions on that day and it still seems to be that way for today's tracks that, generally, do not have the humps anymore and are, generally, smooth enough that the chassis does not need to permit the same magnitude of movement anymore.

 

It would be near impossible to include all of the subtleties of inputs the track provides to the car to simulate this in a virtual world (my engineering specialty) and only a bit less impossible to include the subtleties of reactions the chassis components back to the track. And this changes a bit for each lane, ambient conditions of track tackiness, temperature, sometimes even humidity - we have all seen that these have a not insignificant effect.

 

If my engineering instincts are correct about the frequency dependency, when you make an improvement in speed, it changes the frequency of track inputs - a never ending tail-chasing exercise. The fastest guys have to anticipate track conditions for all the rubber that was laid down since they qualified! I could not have more respect for the people that always seem to get the set-up right for their race. 

 

I've said this before in many previous posts - every time I try to apply my engineering knowledge to slot cars and think I know something that is always true, someone else comes along and whips my tail with just the opposite thinking.

 

I LOVE this hobby!

 

Keep it in the slot,

 

AJ

[Larry Horner]

Ok, I'm really late to this party but I wanted to add one additional bit of praise for the venerable (and way kool indeed) drop arm! Years ago I was inspired by this awesome build by Rick Thigpen: http://slotblog.net/...-iso-grifo-4wd/. In fact I was so inspired that since then, I've built several 4wd cars a few of which handle amazing well for non aero cars. What I personally love is that you have to drive them differently. More specifically they are able to brake much deeper as the front tires are allowing motor braking to occur which is only enhanced by the frontward weight shift during braking. What you DON'T want to do is let them drift out too far while turning as 4 wheels of tire bite can cause a car to snap back into alignment so quickly you deslot ... sort of the slot car equivalent of a motorcycling "high side". But I digress ... the point is that for driven front tires to be truly useful, you want them to have as much traction as possible hence a drop arm design is simply a given.

[TSR]

And Larry, if you had a truly fast car, your chassis with a drop arm would be a great flyer by 2/3rd of an American "Blue King" straightaway, would hit the top of the banking's retaining wall and cause havoc to the seven other cars on the track while tumbing down to rest at the bottom of the banking.
When cars were slow, drop arms MAY have helped, especially with the "mountains" built in the tracks. When lap times on a "King" dropped to below 4 seconds, drop arms became a liability.
I was the first who did away with them in pro racing, and am grateful that most quickly copied that, because there were a lot less cadavers at the bottom of the banking and our cars survived far longer than they did during the drop-arm era. Ask Tony P, I am sure he agrees with this...

[tonyp]

The iso and diamond chassis both eliminated the drop arm with the motor now directly connected to the guide. Better performance as the motors got faster and the glue got thicker.

The drop arm cars by this time were running with the drop arm sprung so tight it no longer moved, so eliminating it was the next logical step.


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[TSR]

Tony, exactly, and it was "one small step for man..."  

[Gene/ZR1]

It was cool thing and the beginning of chassis science of shake, rattle and roll.

AMT had the first side weights to shifted back and forth, who cared and most were never installed. 
Honesty I don’t think anyone back then really thought it had a purpose except for a wheel stand, they just bought a cool looking car and buzzed around the track and fell off on the corners.

g.