New builder needing help

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Loud2ns
Apprentice
Apprentice
Posts: 16
Joined: Thu Mar 15, 2018 7:50 pm
Location: Hudsonville, Michigan

Re: New builder needing help

Post by Loud2ns » Thu Nov 21, 2019 3:52 pm

Speedster wrote:Loud2ns, what type and shape weight will you use to weight the car, how much weight behind the rear axle slot, and what COM are you striving for?
I'm using 1/4 tungsten. Not sure what the COM is.

Sent from my SM-G950U using Tapatalk




Singledad2019
Apprentice
Apprentice
Posts: 10
Joined: Mon Nov 18, 2019 3:41 pm
Location: Milwaukee, Wi

Re: New builder needing help

Post by Singledad2019 » Thu Nov 21, 2019 6:50 pm

I'm using the lead screw ins. We are using the drill press to make the holes, now. My son pulling down the control makes him feel apart of all this. I figured I would get a few wedge bodies from the scout store and we would do it. See how it works out. He could also do some hand sanding if we did large hole car.



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1748
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: New builder needing help

Post by Speedster » Fri Nov 22, 2019 5:59 am

Singledad, would you please give me some information on "lead" screw in weights.

Where did you buy these weights?
Are they actually made out of lead or some other material perhaps the density of lead?
What are their size?
What are their weight?

I know you want to build a very fast car because you bought a track and you're on Derbytalk. Weight placement, and the amount of weight, is very, very important. If you are intending to get a 3/4" balance point you are going to need enough weight behind the rear axle to try to accomplish that. That will probably take about 2 ounces and that is why many builders use 1/4" tungsten cubes. With the rear wheels moved back to the end of the block doesn't leave much room. Even with a stock wheelbase there is not a lot of room.

To be clear, when I think about what you are doing I'm pretending this is your car and you are in a classroom learning how to build a block of wood to go fast down a hill following science. That is your activity and that is what you have asked for.

Your relationship with your scout is yours and yours alone. I and the other racers on Derbytalk are simply wanting to share our knowledge of making a block of wood go down a hill fast using gravity. We are on your side and I suspect we are all going to say the same thing.
Have Fun with your scout.

I wish you the very Best.
Bill



Singledad2019
Apprentice
Apprentice
Posts: 10
Joined: Mon Nov 18, 2019 3:41 pm
Location: Milwaukee, Wi

Re: New builder needing help

Post by Singledad2019 » Fri Nov 22, 2019 8:28 am

The weights are adjustable tungsten 1/2 ounce 3/8. I was drilling 5/16 holes with a spade bit, and then turning them in with an Allen head wrench. All of his other cars have 4 of these behind the axle, and then 2 of them at the point of slightly behind the inch point in front of the axle. Should I be putting the front weight further back?



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1748
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: New builder needing help

Post by Speedster » Fri Nov 22, 2019 12:56 pm

Would you please send a picture of what this weight looks like and also with 6 of them installed in a car. At what point does the car balance with the wheels and axles on it?
Where did you buy these weights and how much did they cost?



Singledad2019
Apprentice
Apprentice
Posts: 10
Joined: Mon Nov 18, 2019 3:41 pm
Location: Milwaukee, Wi

Re: New builder needing help

Post by Singledad2019 » Fri Nov 22, 2019 1:39 pm

I love weights. I found out about them though the build workshop. Their track is rough so they want the weights to screw into bottom or sides. You get 4 equal to 2 ounce for like $20. I have seen them online. However, I think it called hobby town usa. Where I get them. They can be easily cut down with power sander or grinder, too.



Loud2ns
Apprentice
Apprentice
Posts: 16
Joined: Thu Mar 15, 2018 7:50 pm
Location: Hudsonville, Michigan

Re: New builder needing help

Post by Loud2ns » Fri Nov 22, 2019 9:15 pm


Singledad2019 wrote:The weights are adjustable tungsten 1/2 ounce 3/8. I was drilling 5/16 holes with a spade bit, and then turning them in with an Allen head wrench. All of his other cars have 4 of these behind the axle, and then 2 of them at the point of slightly behind the inch point in front of the axle. Should I be putting the front weight further back?
How did the car handle in the transition and flat with 4 in the back? How much steer/drift to get it settled down?

Sent from my SM-G950U using Tapatalk




User avatar
whodathunkit
Pine Head Legend
Pine Head Legend
Posts: 2204
Joined: Sat Apr 25, 2009 5:56 pm
Location: Forgan, OK

Re: New builder needing help

Post by whodathunkit » Sat Nov 23, 2019 1:03 pm

Speedster & Loud2ns,

Sound like Singledad2019 is using tungsten cog weights like these
https://houseofhobbies.com/collections/ ... ducts/5006

In his first photo of the car.. with the open holes and the blue wheels ..
it also looks to me that he is using some tungsten or lead flat screw on incremental weights under the car.. in front and behind the back axle slot.

Singledad2019 Im with Loud2ns on covering up the holes with clear tape and with what he said about weight.

This is going to sound crazy to you guys !
In Big Rig racing where they can weigh up to 4 pounds max.. racing them on a 5Oft wooden track with no center rail and a starting gate height of 30" off the floor.
The 4 pound heavy weight trucks are slower and sometimes don't make it to the finish line. The trucks in the 2 - 3 pound range are faster at getting to the finish line.
Or At least that's what i was seeing at the Fall TMC Big Rig Challenge this year. ( Don't figure!) you'd think the trucks would be the same as the cars for weight.


What type of automobile can be spelled the same forwards & backwards?

Speedster
Pine Head Legend
Pine Head Legend
Posts: 1748
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: New builder needing help

Post by Speedster » Sat Nov 23, 2019 3:14 pm

Yep, that's what he's using. I have both packages in front of me. One has 4 weights. The other box has 2 weights, 23/64" drill bit, 3 mm adjustment tool and instructions. The Toledo store had only one of each, I bought them both and they are not buying anymore. They are getting rid of the Pinewood Derby stuff. By drilling holes from back to front you could end up with a fairly slim car. Something to keep in mind, Tungsten blocks, bars, cubes, plates all come in sizes 1/4" or less.



Singledad2019
Apprentice
Apprentice
Posts: 10
Joined: Mon Nov 18, 2019 3:41 pm
Location: Milwaukee, Wi

Re: New builder needing help

Post by Singledad2019 » Sat Nov 23, 2019 5:18 pm

I like those weights because you easily remove them and reuse them if build fails. I will covering the holes with clear tape if we go that route. My son is more into the one big hole idea so I'm thinking with thicker side connections it could hold up. The track they race on is 42 foot best track that is not in good shape, so no holes would probably be best. There is talk that the owner altered it, so it would be more difficult.



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1748
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: New builder needing help

Post by Speedster » Sat Nov 23, 2019 8:12 pm

Singledad2019, If you have checked your email you will see the rear tungsten block, the front tungsten bar, the 3 tungsten cubes are all 1/4" in height. There is one 3/8" x 3/16" tungsten cylinder to finish it off and give it a 3/4" balance point. The tungsten is all set in double face tape and can easily be removed. This particular car was cut at 5/16" and the desired CoG was achieved without removing any more wood. As you can see the cut areas were covered on the bottom with very thin wood before the weight was installed. The weight is visible because I use this car for educational purposes at workshops.

You will soon begin very, very important work on the wheels and axles and this is where you can gain a lot of speed. Since you are apparently allowed to use bought shaped blocks I would suggest you buy wheels that have been made round. You can buy them and that's all they do, make them round. If you're allowed to do more then that to the wheels then by all means, do it. I happen to buy mine from Derby Evolution. All my cars are set up as 3 wheel rail riders with a beginning drift of 2" in 4'. The car then has its final tune on a Best track. There is a special technique setting up a rail rider with 4 wheels required on the ground. Preparing wheels, axles, tuning and setting up a 4 wheel rail rider can be found on the Derby talk Search function. There will be information found on any question you have on the Search function. I urge you to read as much as you can.
I wish you and your Team the Very Best.

Whoda, your pictures are no longer available under car and truck photos.



Post Reply