I could give a long dissertation on taking a stock Aurora Thunderjet crown gear (one where the teeth are on a perpendicular plane to the axle) and make it true, and .300" diameter, and have the friction points be also perpendicular to the axle. It takes some work. You have to go through 2-10 crown gears to find one that will qualify as workable. Or, you can get one from
Gogo Racing Products and just drop it in the car.
We took a lot of time checking these gears, from all angles, and could not find any discrepancies. At most we found .0005 differential in the teeth, which is so negligible as to not be worth reporting. Let me just say that very few machines can surpass that tolerance level. The workmanship is premium.
So, why do I want to pay $6.50 for a gear? In a word, "ease". If you are a top level competitor, you will pony up for these. Even the casual racer who wants a quick fix way to improve their car will opt in. There is still some shimming to do. Gogo recomends 3-.015" shims for the "no boss" version, and a .015" shim for the gears with the typical boss. Take your pick. Some schools of thought say the more slip surfaces, the better.
One other important aspect, if you're really looking to build a top notch car is that the gears have small enough holes to be able to secure a non-fluted drill blank as an axle. Best size seems to be .635. We did not have any trouble with gears cracking from the installation.
In His Own Words
GoGo Racing Products was created out of the need to have precision replacement parts along with resin bodies for the ThunderJet chassis. I have always made silicone coated sponge tires for my own HO slot cars (magnet cars) dating back to the early 90’s. By the time the magnet car segment of the hobby died out in my area I was already involved with T-Jets again. Well needless to say I took that same knowledge in making tires and applied it to T-Jets. I started selling them nationwide and it evolved from making my own silicone coated sponge tires for my magnet cars to widespread use in T-Jet racing. As everyone already knows silicone coated sponge tires are the tires of choice for Fray/QCQ/VHORS type cars.
Late last year in addition to my SGT tires, I started production of the SuperFast 15 tooth crown gear. Many racers were very happy to finally have a crown gear that would spin true and not wobble. Even Mr. So-Cal himself Rick Jocham used this gear in winning the Individual title at this year’s Fray. In the meantime I started researching other parts that could be made to a higher standard. The new UltraFast 15 tooth crown evolved from that research.
In the coming months GoGo Racing Products we will be introducing several new parts for T-Jets. The first of these new parts is the UltraFast 15 tooth T-Jet crown gear. The can be ordered with or without an inner boss for less shimming. The crown gears without the boss require approximately 0.45 thousandths in spacers for an excellent mesh with the 9 tooth pinion. The gears with the inner boss require approximately 0.15 thousandths in spacers for a perfect mesh. These are very high precision gears that are made out of Delrin. They are machined to .300 of an inch in diameter. This is the minimum allowed according to current Fray/QCQ regulations. They can be installed using an axle ranging in size from .061” to .065” “if rules permit”.
Installing the UltraFast crown gear requires the use of some type of press. I suggest using a press that was made for pressing on wheels. In my case I took an old press that was made for pressing on magnet car wheels. Start by placing the gear in the chassis and any spacer/shim washers on the tooth side of the gear. Find a smaller axle that will move freely through the gear like a .059" (a Tyco 440 Rear Axle) works great. Insert the pilot axle through the gear and add the spacers or shim washers as needed. I recommend set up with .001" to .002" of play in your mesh as to try and eliminate any chances of bind or drag when a car enters a corner. Once you have determined that you have the correct mesh with the pinion you will need to press in the race axle you are going use in your car. Always recheck your installation upon final assembly as just when you think things are exactly where you want it something can shift and make the set up to loose or to tight! These gears can be ordered from my website at www.gohoracing.com . The cost per gear is $6.50 plus shipping and handling.
Sincerely,
Steve Godinez aka "GoGo"
