Building a cubmobile & tips and hints.

Discussions related to building cubmobiles.
clemsontigerfanatic
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Re: building a cubmobile & tips and hints.

Post by clemsontigerfanatic » Thu Apr 21, 2005 4:13 pm

We had 4 boys use our car $3 a piece. $12 a car. Which is still high since
a nice trophy can be bought for $12 and there were only 3 tiny trophies given out. There was zero other costs since every one volunteers.
I guess your paying the DJ $300. Are you getting your monies worth?

Our boys went down the hill one/two times each. I think thats a little steep.How many times did each boy get to race at yours Sporty?

Yes the hardware is more than the lumber especially if you domn't use treated lumber. I've seen where some Districts say you cant use treated lumber.



clemsontigerfanatic
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Re: building a cubmobile & tips and hints.

Post by clemsontigerfanatic » Thu Apr 21, 2005 4:19 pm

Sporty
How do you feel about the Comtech wheels? Do you think there faster
than the ones you had before?



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sporty
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Re: building a cubmobile & tips and hints.

Post by sporty » Thu Apr 21, 2005 5:38 pm

Hmm,

I have not did my time trial tests yet, I was hoping for this weekend.

I'll let you know as soon as i get some times in. I am worried about the lack of spin time. That plays into affect 3/4 way down the track.

Will let ya know as soon as i test and compare.

sporty



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Re: building a cubmobile & tips and hints.

Post by kayjon » Thu Apr 21, 2005 6:31 pm

Our cubmobile derby was not a competition, however two would go down at the time. The boys got as taste of competing with out being timed. The event started at 10:00 and went until 3:00. There were 25 cars in total so the boys could go down the hill as many times as they wished. My best guess is that our car went down the hill 25 times. Early in the day the boys may have had to wait for 4-5 cars to go before them, but towards the end of the day as soon as they got to the top of the hill they could go again.
As far as wheel speed our wheels were used just as they came out of the box. I think the wheels could have been made faster if the factory lube hade been washed out and replaced with a lighter lube. The comtech wheels were on 2 cubmobiles at the event. Ours were the the 8" and the other fast car had the 10".
This was a fun day. It was like watching a full size Pinewood derby with drivers.



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Stan Pope
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Re: building a cubmobile & tips and hints.

Post by Stan Pope » Fri Apr 22, 2005 1:03 am

clemsontigerfanatic wrote:We had 1 car in our District that had a steering wheel with cables. Thats
as close to leverage that I've seen.
I'd think that if you configured levers or a joystick, you could get 2 to 1 or 3 to 1 mechanical advantage, and the large movements that youngsters tend to make would produce smaller movements in the steering. Also, they would be able to hold the car's line more easily against bumps in the road that would try to make the car turn.


Stan
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clemsontigerfanatic
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Re: building a cubmobile & tips and hints.

Post by clemsontigerfanatic » Fri Apr 22, 2005 3:07 pm

I agree.

The tendency is to over steer by pulling to hard on the ropes
instead of gently push with the feet. Maybe one hand for the brake lever
and one hand for the driving lever.



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sporty
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Re: building a cubmobile & tips and hints.

Post by sporty » Fri Apr 22, 2005 9:51 pm

I looked at my rules, I cant do that,

But i did play around with corel draw, FYI, im not the best at it. However i may have came up with a design that might work.

Im gonna add it to my pictures on my web site,

sporty
[/img]



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sporty
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Re: building a cubmobile & tips and hints.

Post by sporty » Sat Apr 23, 2005 2:46 pm

Okay, i had to change corel draw to jpeg, used a marker, don't look to good, but it's a idea anyhow.


CUBMOBILE TIME RUN/TEST COMPLETE -

(95 feet used)

RED MOBILE BLUE MOBILE

(R) 30.37 SECONDS (B) 24.78 SECONDS



CHANGED DISTANCE TO 89 FEET-

Red cubmobile could not go 95 feet, blue could, but shortened anyhow.

(R) 26.53 SECONDS (B) 24.75 SECONDS


ADDED 1 BRICK FOR WEIGHT ON RED CUBMOBILE NONE ON BLUE ONE

(R) 28.24 SECONDS (B) 23.85 (LIGHTER SON on this one race, blue one only)

ADDED 2 BRICKS FOR WEIGHT 2 RED ONE, NONE ON BLUE

(R) 27.09 (B) 25.44


Fastest time Red - 26.53 Fastest time Blue - 24.75 (not gonna include lighter son time)

Slowest time Red - 30.37 Slowest Blue - 25.44


Thougt weight was the issue, it helped some but did not make up enough time.

More test runs to be done, was in the 40"s today, didnt want to kids to catch a cold.

Comments - The comtech wheels need some work, either different bearings or taken off and i'll use the ones from the blue cubmobile.

reminder, 10 inch comtech - red, 12 inch- blains farm n fleet, blue.

reminder 2 - in the race last year, I saw no differance from 10 inch to 12 inch when properly lubed.

Thoughts - comtech wheels easier to use/steer, for speed they are slow.

Sporty




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Re: building a cubmobile & tips and hints.

Post by sporty » Sat Apr 23, 2005 3:07 pm

Okay I wanted to add some reply to some earlier questions-

This years race entry is $8.00 per race, $10.00 at day of race.

Trophys for, 1,2,3. Patches for all racers. (TROPHY WAS APROX 10 INCH TALL LAST YEAR) trophy's were paid for buy local area donaters.

Best desgn, trophy.

1 test run per car. double elimination race. for example my son did not loose a race until for the 1st place. He over steered and hit the hay bail. this would then put him in for a tie for 1st. But he raced the same person again and lost by like 3 inches. Ending up with second.

When he crashed into the hay bail he was in the lead, you run on different side of the ramp each race, one ramp is slower than the other. I think if the dj, announcer had not announced that the race was for 1st place, he might have one, cua he got all nervous when that was announced.

fastest car moves on to each level

pre race inspection, no working on cars during the race.

I think my son went down 6 or eight times. Id have to watch the tape again.

sporty



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Re: building a cubmobile & tips and hints.

Post by sporty » Sat Apr 23, 2005 6:11 pm

wanted to add weight info

red stock - 26 pounds

blue stock 47 pounds

1 brick - 8.5 pounds

2 bricks = 17 pounds

brick were close to center of vehicle.

added this 4 previous mention of time trial runs.

weight diff was 4 pounds, still almost 1 1/2 second time differance.

i re- did a stop watch spin time,

red car - comtech wheels, 18 seconds.

blue car - 2 minutes 30 seconds.

I have not done anything to the wheels on the blue car since last year.

sporty



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Re: building a cubmobile & tips and hints.

Post by sporty » Sat Apr 23, 2005 11:29 pm

Okay yet some more info on the wheels.

I added 3 photos to explain what i'm about to talk about.

http://home.insightbb.com/~ryan.johnson ... ip-25.html


I took the 10 inch wheel off, I lubed with wd-40, was trying to loosen up. even tho its sealed, No luck still a spin time of 20 seconds.

However I came across a discovery. Now when I mounted mine, I had a small washer to just cover the back inner race. So to no affect the black plastic (sealed bearing area).

Well, With out the washer touching that, I can get a spin time of 50 seconds. So the flush surface is affecting the bearing movement when securing both sides.

I also tried to remove bearings from wheel, I had no luck, they may be pressed in. I didnt not try overly hard tho either, I didnt want to wreck or damage anything.

A buddy of mine gave me a old wheel chair last week for parts, if I needed it, I took off one of the 8 inch wheels on it. Rusty as all get out.

I sprayed some wd-40 and gave it a spin, WOW 3 minutes and 28 seconds !! This bearing is a non-sealed bearing BTW. I also realized the inner race protruded on both sides. Thus allowing both ends to be secure and not affect the bearing.

Why does free spin matter - Well in my view, a couple of reasons, the easier the spin, the faster the wheel can spin and get there easily and quicker, when under a load.

Also once you go off the ramp and you are 1/2 way or 3/4 way down the track. That friction or lack of friction plays a huge role in keeping the speed going or causing drag and slowing the cub mobile down.

Most cub mobiles that my son won against, lost there speed at around 3/4 the way down the track. They were running 12" wheels and 10 " inch wheels, but there spin time (saw in pit lane) was not there. Now there is all those other factors to calculate in. But at this point im on the topic of just the wheels.

Infact the car that got 3rd place last year had 10 inch wheels, is a friend of my sons and I went over there before the race and sprayed some pentrating oil adn then some wd-40. So I cant say enought to use those to oils on the wheels.

3 thoughts-

1- The sealed bearing is not a good option for the cub mobile, 2 reasons on my view. (to thick of oil used) (no protruding inner race, affecting bearing spin).

2- If you gonna buy them, Get the non-sealed bearings. 3 minutes and 28 second spin time on the 8 inch, will likely be the same on a 10 inch non sealed bearing loosened up and wd-40 used.

3- ComTech, AKA northwest. I hope you visit and read this and enjoy the help I have provided. To help future Cubmobilers on tire choices and bearings. Any chance they will donate 4, 10" wheels with non sealed bearings to me for my time ?? (with protruding inner race and with a thinner bearing oil) :D :D

Sporty

PS- Stan has sent me some design idea's on steering will post later tommaro.



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Re: building a cubmobile & tips and hints.

Post by sporty » Mon Apr 25, 2005 11:54 pm

Posted on my website some steering idea's from Stan.

Sporty



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Re: building a cubmobile & tips and hints.

Post by sporty » Wed Apr 27, 2005 12:34 pm

For a Couple of days the info was flowing pretty well. I have not heard much from COmtech in the past coupld of days.

I was hoping to see some replys, with either added info or comments on the tire/rim/bearing issue.

My theory at this time is that with talking with other people -

That the sealed bearings may work well for down hill events, where there is a continue slope, versus my application where the event is 90% flat and smooth.

Kinetic energy would come into being a biggere factor along with free spin time of the wheels.

Also the Lighter wheel would work against you on a 90% flat surface with just being launched from a ramp

I mean we have heard from other's that the winning vehicle under a hill type race, the comtech wheels proved to do well. I wish I had resources to confirm that this is 100% factor and not the slim wheel design making it easier to handle the cub mobile.

FYI, Comtech sent me a e-mail letting me know, They will not refund the wheels. There return policy is they fix defective parts and return. So I have 4 wheels that I will not be using in the race, unless I can find a way to solve this problem.

sporty
Last edited by sporty on Wed Apr 27, 2005 1:28 pm, edited 1 time in total.



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Re: building a cubmobile & tips and hints.

Post by Stan Pope » Wed Apr 27, 2005 1:27 pm

Be careful when making decision based on "spin time". Two big factors are:
1. friction in the bearing, and
2. inertia of the wheel.

Increasing the inertia in the wheel will increase spin time, even if there is more friction in the bearings!

Decreasing friction in the bearing will increase spin time.


Wheel inertia should not be as big an issue with these cars, because the load is proprotionately much heavier than with PWD cars... I think.

Rolling friction (depends on tire material) will be a big issue, with softer tires offsetting improvements in bearing friction.


Stan
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sporty
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Re: building a cubmobile & tips and hints.

Post by sporty » Wed Apr 27, 2005 1:39 pm

Stan,

Correct, I have spent alot of time in recent days looking at a wide variety of factors and data and information from other contacts.

The theory and thoughts are acurate and more importantly until someone can help assist with giving more data. I have not seen the type of info or data that I so far have provided.

But I am hoping others will provide more data that would help in proving or dis proving this info that I have started upon

It does not appear Comtech is going to donate or help in furhting to prove or dis prove what I have begin to see.

I am not just factoring in spin, time but also kinetic energy, size and weight. I also mentioned there being 2 senerios for the race, one of downhill and the other 90% flat with a ramp used.

I have mentioned that I feel the comtech wheels would be good for the downhill events but not for the 90% flat with a ramp used races.

Most of the other cub mobile builders/racers and mentioned in the forum that they used downhill with the comtech wheels and did fairly well.

But I hope we can get into data and facts with the wheels. I hope you will join with me to provide data and info, and tests to either prove or dis prove what I am starting to find out.


I also ask comtech to pride some of there testing results of the wheels and others they tested against. To help with proving or dis proving my info that I have started to gather. If its a better wheel for one race or another type of race. Lets get it out there for future racers.
Thanks

sporty



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