Completed our first Cubmobile, had a blast!

General cubmobile related topics.
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Teeeman
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Completed our first Cubmobile, had a blast!

Post by Teeeman » Mon Apr 25, 2005 3:46 pm

We completed our first Cubmobile in 3 weeks from the time we knew the race existed... and raced to 1st Saturday!

We did some things different than the base design.
We used steering linkage to move the seat back as far as possible, and also to provide a 2:1 steering ratio (this both de-sensitized the steering and made the steering require half the effort).
The result: Our car was stable and controllable, the rest of the cars went out of control about 50% of the time (many ran into the crowd or other cars).

We also used some Pinewood style techniques on the car... we raised the right front wheel and offset the seat to the left to keep it airborne.

Can anyone on here host pics?

I think for safety's sake anyone building a new car should consider some type of simple linkage steering to give the rider more control. Steering was the number one problem at our race... and for cars under control the other car running into them was very, very common.

Terry


"I dunno..." - Uncle Eddie, Christmas Vacation

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sporty
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Re: Completed our first Cubmobile, had a blast!

Post by sporty » Mon Apr 25, 2005 11:08 pm

CONGRATS !! To you and Your son.

Ya I couldnt figure how to posts pictures, so I did a website.

If I may ask, What kinds of Wheels did you use ? Was it mostly a downhill event ? or a ramp and then mostly flat ?

Sporty



Teeeman
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Re: Completed our first Cubmobile, had a blast!

Post by Teeeman » Wed Apr 27, 2005 2:29 pm

Pics would be worth a 1000words, but here goes...

We had a run in a parking lot, it was a slight downward grade the entire length of the track (about 100feet).
The starting ramp was about 5 feet high at the rear, and about 20-30 degrees (I am guessing).

The starting system was Army soldier volunteers who held the cars and released them by hand when the announcer gave "go" over the PA... and the timers likewise were volunteers at the finish line with stopwatches.

We had a bit of a short stopping distance from the finish line to the barriers (large pallets of yard timbers with bails of hay in front of them). Many a Cubmobile ran into the hay full-speed.

The minimal safety improvement for next year would be to line the course exterior with bails of hay... we had numerous cars careen into the crowd. Some kind of wider start ramp with bailed hay used as a median would be a big plus too... we had countless spinouts and "hooked together" events between cars.

Some of the cars that didn't lose control still couldn't coast to the finish line, even with the reasonable (2-5 deg guesstimated) downhill grade.

Pre-race inspection was non-existent. Nobody checked overall dims of cars, nor wheel diameters... in particularly, nobody inspected the seatbelts and brakes. Many a cub went flying off their car in the wrecks Saturday (safety belts didn't work)... and many a cub went nearly full speed into the barriers at the end of the track (I said pre-race it seemed to me the barriers should be back about 50-60 more feet!... they were about 30 feet past the finish line).

Our car didn't lose control a single time, and stopped 10feet short of the barriers every single time.

We used a piece of tire (someone conveniently had a blow-out at the entrance to our neighborhood about 2 weeks before the race :) ) and the "standard" brake design... nothing fancy... worked beautifully.

We also practiced a lot with our car... I think that would make a WORLD of difference for most cubs.


Wheels: We used the Commtech 861-1.5 (3/8" ID bearings) for ours.
The 3/8" axle (steel rod from Lowe's) worked well for my son and his weight without adding bricks in our weight box. With the bricks, around the neighborhood, still fine... but we slightly bent the left rear wheel axle(our car was offset seating, left rear was most heavily loaded) enough to establish a negative camber on the wheel but not enough to bind anything up.
I removed the bricks and my son made 5 more runs without issue.

The shock load at the bottom of the ramp is what damaged our car... we had (with Cub on car) 92lbs of force at the left rear wheel (measured with a simple bathroom scale).
We had 115lbs at one point... but since the wheels are rated for 100lbs... I dropped the weight back some by removing some of the brick load.

I wanted to ride too, but the wheel/axle combo was too weak.

I have already priced a 10" and 11" wheel from Commtech for next year... these offer a choice of 1/2" or 5/8" ID bearings and a 150lb load rating.

The total cost just to switch will be over $110. Wheels go from $5 each for the 861 (8") model to $15 apiece for the 11" wheels... due to lower demand for the larger wheels.
The steel rod also goes from $7 for 3/8inch rod (36inch length) at Lowes to mail-ordered (McMaster Carr) $19apiece for 5/8" rod.
That and the clamps (metal instead of plastic) jump to $3 apiece (need a minimum of 8 ).

But, the car will be able to handle me then... without bricks... and my son with a full load of bricks :)


Terry


"I dunno..." - Uncle Eddie, Christmas Vacation

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sporty
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Re: Completed our first Cubmobile, had a blast!

Post by sporty » Wed Apr 27, 2005 2:42 pm

Thank You, for so info. ALot of detail.

The race track that the local pack has -

length around 120 feet, ramp angle i woulf guess over 30%.

The ramp is like 20 feet long, they are mostly level at top, mabe a 5 or 10% down angle, then to a 30% angle. (aprox)

The ramp, has a lever action release of the cars. In the middle for both vehicles.

A light tree at the end of the run, buy laser.

Hay bails in between the tracks and on the outer edge of the track. Hay bails also 15/20 feet after the tree light. The year before they used 2x8 down the middle, the kids would drive over that and bump into the other driver sometimes.

No flip overs, mostly they run into the hay bail and stop.

All cars finished the track except the ones that crashed into the hay.

Last years car, dry weight 47 pounds, my sons weight 38 pounds = 85 pounds.

the new red one, 26 pounds, add him in = 64 pounds,

now we did use brick for the test runs to compare the two vehicles, ended up with a weight differance still of around 3 / 4 pounds,

We can not add weight to out cars, I did this as testing purpose only.

Once again, thanks 4 the info.

Would love to see some pics of your sons cubmobile, Perhaps a free website can help with that.

sporty



Tim
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Re: Completed our first Cubmobile, had a blast!

Post by Tim » Wed Jul 13, 2005 12:25 pm

Teeeman wrote: (snippage)
The total cost just to switch will be over $110. Wheels go from $5 each for the 861 (8") model to $15 apiece for the 11" wheels... due to lower demand for the larger wheels.
The steel rod also goes from $7 for 3/8inch rod (36inch length) at Lowes to mail-ordered (McMaster Carr) $19apiece for 5/8" rod.
That and the clamps (metal instead of plastic) jump to $3 apiece (need a minimum of 8 ).

But, the car will be able to handle me then... without bricks... and my son with a full load of bricks :)


Terry
As long as you're ordering by mail, you might want to take a look at Aicraft Spruce and Specialty. They have 5/8 inch 4130 rod for $2.05/ft That would be about six or eight dollars per axle instead of nineteen.. Twenty bucks is twenty bucks.
Bear in mind, that's normalized steel -- you might want to temper it to make it stiffer after you drill it.
http://www.aircraftspruce.com/catalog/m ... 130rod.php

Also, if you know the outside dimensions of the bearings, you might go to
http://www.bocabearings.com/Default.aspx
and see what you can find. You might find a bearing that would let you upgrade the axles on the eight inch wheels.


Tim

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