New LCG Cubmobile Design

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Cubmaster712
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New LCG Cubmobile Design

Post by Cubmaster712 » Mon Nov 05, 2007 12:01 am

Hi Everyone

This is my first post, done so at the urging of others in my district. I just wanted to share our design with everyone.

First off, these changes we've not done in order to improve speed, but safety. Second, after completing our 5th race with this design with no adverse effects, we would like to share our sucess, and explain a little about where the changes came from.

1st issue: feet being sucked under the cubmobile and instability (rocking back and forth) - the solution was fairly simple, and that is where we ended up with our "v1.0" design. See the compare picture. We "Lowered the Center of Gravity" (LCG) by changing the single 2x4 center runner with 2 2x4s running down each side and adding a bottom panel of 3/8 ply. This was our first step and was wonderfully sucessful.

2nd issue: difficulty steering - Kids we're not getting used to steering with their feet, and loosing control when a foot slipped off. The solution was a simple port of a design I once saw at a soapbox derby race using a long pipe for a steering column, and wrapping the rope around it. A few eyelets for redirecting movement of the rope, and it was done. The steering wheel is a flat piece of solid 1" ply with a mount on the back (to keep the pipe from coming through the steering wheel in case of a harsh accident.

3rd issue: brake failure - overzealous braking sometimes lead to a failure of the lever. Also, sometimes a nut fell off, sometimes a cub didn't look on the right side of the cubmobile and "lost" the brake lever. Solution was to add a second, and fully redundant, brake lever to the opposite side. It can stop on a dime now.

4th issue: curing general instability - moving the weight back. This allows the front end to have less momentum when turning, making the joints move smoother and more precise.

We also toyed with foot brakes, which compromised safety. So we eliminated them.

My next magical trick will hepefully be an offroad version of the v2.0 - an LCG Rally design.

Let me know what you think.

Image

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Stan Pope
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Re: New LCG Cubmobile Design

Post by Stan Pope » Mon Nov 05, 2007 12:36 am

Looks like some excellent concepts! Congrats!


Stan
"If it's not for the boys, it's for the birds!"

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sporty
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Re: New LCG Cubmobile Design

Post by sporty » Mon Nov 05, 2007 4:55 am

Pretty neat idea and design.


Nothing never wrong, when it comes to trying to improve child safety !


Thanks for posting the pics and talking about the changes you have made.


Gee, we would enjoy seeing you post more here. We don't bite !


I have seen a few of the plywood bottom Cubmobile's, but your's is the 1st that is that low and the first I have seen with tha style of steering that you have came up with.

Sporty



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Re: New LCG Cubmobile Design

Post by Teeeman » Tue Nov 27, 2007 11:06 pm

Cool designs!

We tried a hand op linkage steer that needed work to be good... this is cool!

Our foot op linkage steer was a success... this look like you found the consummate hand steer car... nicely done!


Matter of fact, this ought to be the "official car design" in the handbooks!!!



-Terry


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sporty
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Re: New LCG Cubmobile Design

Post by sporty » Tue Nov 27, 2007 11:32 pm

I was hoping that the BSA would start selling some of th parts from the All American soap box derby.

Esp the steering system. The modern or vintage steering system.


Then again, cost is a issue also.


But it sure would be nice to see the old style soap box derby racers built and used for (cubmobiles). The wooden ones.

That's why I had my plea not to long ago, that I posted in the Cubmobile forum.


Sporty



jsta6
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Re: New LCG Cubmobile Design

Post by jsta6 » Sun Mar 16, 2008 3:45 pm

Hello.

Does anyone have any plans for this new style cubmobile? Or know of a URL or website that has the plans?

We are having our district race soon and we want to make this new style available to the packs.

TIA!



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Re: New LCG Cubmobile Design

Post by jsta6 » Sun Apr 13, 2008 11:00 pm

OK, I don't have the plans drawn up yet, but here are some preliminary pics of the car we built. Most all of the pieces I used to build the car were from stuff I literally found in my shed. It is pretty simple, 2x4's, plywood, bolts, screws, etc.

Here is the car in its first stage. We used the 28" axles and 52" frame 2x4's that are the same size as the old style cubmobile. Plywood was 48" x 20" IIRC. We originally used the 8" comtech wheels, but we realized the car would be to low, so I ordered some 10" comtech's. A carpenter buddy helped us with this first stage.

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Then, I made the seat. I used some old "pleather" and some thin foam that I had laying around my shed. I actually had to keep trimming the seat bottom and back to make them smaller and smaller, as I only had so much material and it wouldn't cover it all at first. I used some 3M spray glue and a staple gun. The seat braces behind the seat are the same used for the old style cubmobile, just trimmed down.

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So, wheels were on, seat was in, now we had to make a foot rest because the seat set was back so far. Problem was, our tigers were to short, and our weblos were to tall, so we had to make an adjustable foot rest. A buddy suggested we notch the frame and notch the foot rest.

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Next was the hand brakes. One of the mom's had a neighbor with a router, so we gave him the 2x4's to make oval's in it for the boys hands.

They worked great, but I got a little ambitious, and I wanted to make a real steering wheel instead of using the rope as a bridle. I grabbed an old broomstick and I cut the hand brakes down some and I made an adjustable steering wheel. The wheel moves up and down about 4" to accommodate our needing to move the adjustable foot rest that we had made earlier.

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I tied some thin rope around the steering wheel column and I ran it through some eye-screw things and then, one cool car:

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Now all we have to do is re-make the hand brakes that I cut up for the steering column supports, and we should be done.

We are going to try to get some plastic stuff that they make signs out of to see if we can make a body kit that resembles a 32' Ford.
Last edited by jsta6 on Fri Apr 25, 2008 6:52 pm, edited 1 time in total.



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sporty
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Re: New LCG Cubmobile Design

Post by sporty » Mon Apr 14, 2008 12:55 am

Wow, it looks great and you all did a really nice job !!

thanks for sharing the build with us.

Perhaps many may start to create and build the New Low Gravity design.


Thank you so much again for sharing, we look forward to more pics and great info.

Sporty



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Re: New LCG Cubmobile Design

Post by Teeeman » Mon Apr 14, 2008 10:28 am

Have you raced with the new Commtech wheels?

:)


FYI.... you can remove the bearing seals with a small screwdriver or pick, flush the grease with WD-40 and compressed air... and then simply give each bearing a fresh shot of WD-40 before each run.


-Terry


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Re: New LCG Cubmobile Design

Post by Cubmaster712 » Mon Apr 21, 2008 6:06 pm

Hi Everyone

I'm glad to see all the interest in the LCG. I've received a few requests for designs, and I'd love to publish it, since the current design has been around since I was a Cub! If anyone can help me put that together, I'd appreciate the help.

I'll put together a "napkin" sketch and parts list, so anyone can build it. You can contact me directly through my email account - just go to the main page of where the pictures are in my orginal post and there is a link there.

Thanks!

Dave



jsta6
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Re: New LCG Cubmobile Design

Post by jsta6 » Fri Apr 25, 2008 7:49 am

Hey all, sorry it took so long to reply...I was really burnt out after the derby. Everything was so last minute. I built the body and made the wheels the night before and the wife put the flames on right before the race.

Wow, wow and wow again!

I will post information ASAP on how to build something like this. It was a first time for me, and it was very last minute getting everything done. We didn't do anything as far as "toe in, toe out", "four corner weight distribution" or anything like the stuff that is in Sportys write up. Maybe next year.

Our Weblo's and Tigers got second place in their respective categories, and our tigers won the award for the fastest car of the derby! There wasn't any awards for design or anything like that, I think that we just forgot to do stuff like that, it was our first cubmobile derby.

roadster back (hard to see the license plate that says "PCK 420":
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my son max's run:
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my son max with the car and Miss Teen Hollywood: (after the hub caps fell off)
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My son ben car:
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my son ben car 2:
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Darin McGrew
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Re: New LCG Cubmobile Design

Post by Darin McGrew » Fri Apr 25, 2008 9:41 am

jsta6, can you reduce the size of the construction photos that you posted on 2008/04/13? 1528px is much too wide. Half of that would be much better.

Thanks.



jsta6
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Re: New LCG Cubmobile Design

Post by jsta6 » Fri Apr 25, 2008 6:53 pm

Darin McGrew wrote:jsta6, can you reduce the size of the construction photos that you posted on 2008/04/13? 1528px is much too wide. Half of that would be much better.

Thanks.
Done. Sorry. :mrgreen:



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Re: New LCG Cubmobile Design

Post by derbyspeed » Sat Apr 26, 2008 10:57 pm

Been wanting to build a cubmobile for a long time and we are planning some races in the early fall. Since now seeing this design on Derby Talk I have the fever. I never thought the one in the scout How To manual was all that stable. This set up seems like something you can work with and actually make it look like a car.

Here are a couple of pictures in the early stages:

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I changed the design a little, going with a jacked up back end (so it would look more like a dragster :biggrin2: ). Hopefully the front end won't drag! Using some cheap lawnmower wheels for now (they were free!).

May have to add a parachute or an ejection seat - never know :mrgreen: .


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"Do or Do Not, There is No Try"

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sporty
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Re: New LCG Cubmobile Design

Post by sporty » Sun Apr 27, 2008 12:49 am

The only design flaw and common flaw i have seen with most cubmobiles.

Two things and both are safety !

the white lawn more wheels, With out a bearing in them. I have seen several of these fail !

The axle or bolt through the center of a 2x4.

If using this method, I recommend bolts to ensure no splitting of the wood during the racer.

Lighter drivers seem to not have a issue, heavier drivers do.

So two bolts in the end at each end can help hold it together, if it would fail. or a block of wood on the top and bottom of the wood.

Alignment is also hard to fix or correct with that method.

Once the whole is out of shape, epoxy glue is the best chance to retain the proper shape / alignment.

I like to be-able to adjust and tweak, accounting for driver weight, axle alignment.

This axle bolt assembly makes it very hard to correct that.

The drivers weight alone can bend that axle .015.

Thats with the axle machined mounts I had made for mounting of axle rod.

Unless you have a really good drill press and can adjust it enough to drill into the ends of the 2x4's.

Not likely to see .030 or better. Then the wood just indents around the axle bolt.


Just something to toss out there for you to think about before you get to far along in the build.

LCG is better, but if a poor axle or alignment process is in place. It's not likely to over ride the LCG design.

I actually prefer not to say that. Because i like the design. It's just where the most important part of the build is. It Has a assembly flaw.

Sporty



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