167 replies to this topic

[Alan Draht]

Final result:  Five pairs of K&B dragster tires and wheels trued to 1-3/8" diameter.

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[Alan Draht]

I have acquired the correct lengths of vintage 1/8" x 5-40 threaded axles to install K&B dragster wheels and tires on my Husting and Maldonado replica fuel dragsters.

 

The K&B's will fit fine on the Husting dragster because the straight rail magnesium frame assembly is narrow at the back of the car compared with the Maldonado car which is a true magwinder frame with a wide rear end that tapers down to 3/4" at the front.

 

The K&B dragster wheels will not fit on the Maldonado dragster because the Weldun spur gear's set screw hub positioned tight against the K&B wheel's 5-40 cinch nut and hub, in combination with the car's wide rear end, pushes rear track width beyond the 3.25" dimension allowed by Rod & Custom magazine's class rules in 1966.

 

As revealed fairly recently by Manuel Maldonado himself on YouTube videos, he devised some radical ways to reduce rotating weight and maintain a legal rear track width, such as eliminating the Weldun spur gear's set screw hub. 

[Phloidboy1]

Did you get to run some time trials?

[Alan Draht]

I did test both this car and my Husting dragster replica on Chicagoland Raceway's drag strip on two separate occasions.  IIRC, these two test sessions occurred in May and June, 2021.  These tests took place on weekdays when the track was closed, so there were no other racers around, no distractions.  Mike Swiss was very accommodating.  He was instrumental in helping to stage these runs, adjusting voltage, interpreting test result data, etc.

 

The Maldonado dragster's best elapsed time was about 1.24 seconds.  To the best of my recollection, the Husting dragster's best time was 1.16 or 1.17 seconds.

 

The Maldonado dragster was heavier and thus slower than the Husting dragster.  On its best run at 22 volts the Husting dragster stopped just short of hitting the end wall.  Both cars used 6 volt Ram 850 armatures.  Based on observations of these initial test runs, running replica Top Fuel Eliminator dragsters at the same voltages used in 1965 -- 30 volts, 36 volts -- looks like a sure way to wreck them at Chicagoland Raceway, and probably other raceways as well.

 

Both cars used "hairy" braid, same as the originals.  This braid burned up in a few runs and had to be replaced.  Even with replacement, both cars were only good for a handful of test runs, and then they ran slower with each successive run, so I ended testing for the day.

 

Following those two test sessions, I completely disassembled both dragsters. and rebuilt them with 3 volt Ram arms. I revised the Weldun 64-pitch gear ratios from 3:1 to 2.83:1 on both cars.  I reduced the nose weights of both cars, switching from low-temp lead alloy (Bismuth) nose weights to tungsten weights which are less bulky and much easier to calibrate.  I ditched the 1965 period-correct "hairy" braid and vintage guides, replacing them with modern guides and standard braid.  I installed guide flag "up stops" on both cars to keep guides and braid firmly planted in the slot for improved electrical contact, reduced arcing.

 

All of this work took time to complete and when the rebuilt cars were ready for a new round of testing, it was July or August, 2021.

 

By that time, Chicagoland was in the throes of importing/ distributing new IRRA-approved CR-102 Retro motors.  Understandably, Mike had no time to spare supervising and/ or assisting with my testing program on Chicagoland's drag strip.

 

So, I put the rebuilt cars away.

 

Do I think these lighter, more powerful (3 volt Ram arms!), higher-geared, more efficient replica dragsters are capable of setting faster elapsed times?  Yes, I do.

[Tom Katsanis]

Great e.ts for 6 v arm hope you get a chance to give them a run soon

If you do Alan please let us know what your running on 16v so we can compare it to what we are getting thanks.

[Phloidboy1]

Changing the gear ratios, did that affect the gear guard?

[Alan Draht]

A single machined gear guard protects both the pinion and the spur gears of a magwinder.  It must be designed to accommodate the Weldun 64 pitch gear sets incorporated into the magwinders Gene Husting and Manuel Maldonado built in the 1960's.

 

The largest diameter aluminum 64 pitch spur gear Weldun made was 71 teeth.  The formula for determining the fixed center distance between two meshing 64 pitch gears yields a total tooth count (spur and pinion gear tooth counts combined) of 92 teeth.

 

The Weldun gearing sets Husting and Maldonado used in building and racing their magwinders were identical.  The gear sets all totaled to 92 teeth.  The formula allows the builder to change gear ratios using fixed pinion and spur gear centers as long as the tooth count totals to 92.  So, 71t spur + 21t pinion = 92.  70t spur + 22t pinion = 92.  69t spur + 23t pinion = 92... and so on...

 

Magwinder Weldun 64 pitch gear sets and ratios ranged from 71t spur + 21t pinion to 66t spur + 26t pinion.  The corresponding gear ratios ranged from 3.38 : 1 to 2.54 : 1.

 

The gear guard's size and shape is determined by the gear set size/ ratio range and the largest gear pitch diameters at each end of the range.  For magwinders, the largest Weldun 64 pitch spur gear is 71 teeth and the largest 64 pitch pinion is 26 teeth.

 

The gear guard is machined to just barely clear the the largest diameter spur and pinion gears used in a magwinder's available gear sets.

 

The section of the gear guard which surrounds the large diameter spur gear must be machined thin enough in profile to allow sufficient clearance above the track surface.  Rod & Custom magazine's magwinder drag racing rules in 1966 limited rear wheel/ tire size to 1.375 inch maximum diameter.  This rear wheel/ tire maximum size constraint of 1.375 inch diameter limits the size of the Weldun 64 pitch spur gear to 71 teeth.  Clearance tolerances using a 71t or a 70t spur gear are very tight.

 

Machining a magnesium gear guard to be perfectly concentric with the gears when mounted to the magwinder's frame and provide adequate clearance around both the gears and above the track surface is a tricky process.

 

This response provides more detail than most people want to read about, but necessary for builders of replica Husting and Maldonado magwinders.

[Phloidboy1]

Yes, thanks for the extra detail & I totally can relate. Constructing the gear guard to the largest gear combination would allow easy adjustment for various gear ratio changes. Sometimes I think the gear guard is harder to create than the frame rails, lol

[Alan Draht]

Gene Husting's 4-part series of 1965 - 1966 Rod & Custom magazine articles detailing construction of his famous 1 second ET fuel class magwinder dragster do not describe or illustrate how he machined his gear guard, other than to say that it was fabricated from 0.10 inch thick magnesium sheet.

 

The only way I could figure out how to machine the gear guard accurately and error-free is by using a rotary table with 1/16 inch end mills to cut out the guard's interior openings concentric with the spur and pinion gear shaft centers.  While Husting used 0.10 thick magnesium sheet in the mid-1960's, I cut my gear guards out of 0.13 inch thick magnesium sheet 55 years later.

[Alan Draht]

When it came to fabricating the side rails, Husting used 1/16 inch thick magnesium sheet.  He took two pieces sized 1.125 inches wide by 9.50 inches long and bolted them together at the four corners with 2-56 brass screws and nuts to ensure that both frame rails are identical when they are drilled and cut out.

 

Husting used a drill and a "wire hacksaw blade" (which cuts in both directions) to cut out the interior openings of the side rails, filed the saw marks smooth, and then cut out the frame in its entirety.

[Alan Draht]

Although I followed Husting's frame fabrication directions exactly, I was never confident with his method of using a hacksaw to cut out the interior openings or the frame's exterior shape.  Instead, I milled the frame's openings and exterior outline using 0.125 inch end mills, then used a file to smooth and finalize the shapes.

 

Milling the frame maximizes control over the fabrication process, but it is time-consuming and tedious.

[Alan Draht]

I have the materials, component parts and motors to build a few more magwinders replicating other class-winning dragsters from the Rod & Custom dragster contest era.

 

My only real hang up with building another vintage magwinder replica is frame fabrication.

 

Can you tell me how you fabricate your magnesium frame dragsters?

 

Do you use a hacksaw to cut out the frame's interior openings and exterior outline shape?

 

Have you ever used a table-top jigsaw or scroll saw to fabricate your magwinder frames?  If so, can you recommend a machine that will cut through 0.125 inch thick magnesium sheet (2 x 0.063 inch thick sheets bolted together) ??

[Phloidboy1]

Yes, I have used a tabletop scroll saw, very slow, I drill out as much material as possible, then use a jewelers saw or the scroll saw for interior slots, i use a full-size. hack saw & jewelers saw for exterior perimeter contour, also have found a small meat market hack saw very useful

[Phloidboy1]

[Phloidboy1]

MOLDY III Project continues, added brass weight upfront, drop pick-up down pressure spring, & prototype body cover iffy scratches dents, wrinkles, temporary driver.

[Martin]

WOW, truly amazing build.     well done,

 

P.S. not sure about the driver, maybe that test run scared him to death ?

[Dave Crevie]

Right! Turned out beautiful. 

 

I used to put troll dolls or dinosaurs in my cars for drivers. The crazy hair of the troll dolls drew a lot of protests. Drivers were afraid it would get tangled up in their gears. My answer? Stay ahead of me!

[Phloidboy1]