Anyone good with cutting foam inserts?

[obessedwithrc]

@LibertyMKiii or anyone else good with cutting foam tires? I'm looking for help cutting a 2.2 crawler foam insert. More specifically, I'm looking to use the insert with a short-course wheel, which is 3.0 inches v. 2.2. inches. I need to enlarge the center hole from 2.2 to 3.0 inches. I tried this with a sharp foam cutting razor but the whole ended up lopsided and looked like it was attacked by a shark. Any ideas?

 

[Tex Koder]

@LibertyMKiii or anyone else good with cutting foam tires? I'm looking for help cutting a 2.2 crawler foam insert. More specifically, I'm looking to use the insert with a short-course wheel, which is 3.0 inches v. 2.2. inches. I need to enlarge the center hole from 2.2 to 3.0 inches.

How thick is that foam?

Sounds like you need a custom foam cutting template to guide your cut..

I tried this with a sharp foam cutting razor but the whole ended up lopsided and looked like it was attacked by a shark. Any ideas?

Pics of shark attack?

 

[slick2500]

I tried hand cutting foams once and no matter how much I tried they were never straight.

 

[LibertyMKiii]

You may need a hotwire cutter and even then its hard. You have to use something to guide it along the cut otherwise it will be pretty ugly.

 

[Tex Koder]

What's the outer diameter of that foam piece?

Let me know..
So I can draft up a cutting guide later today.

 

[obessedwithrc]

These are the tires: https://www.amainhobbies.com/jconcepts-landmines-2.2-rock-crawler-tires-2-green-jco4050-02/p1478018. The dimensions of the foam are 2.2 x 5.79 inches.

I did find 3d printed inserts, but again, they are designed for a 2.2 wheel. https://www.ebay.com/itm/385671504688.

This is the truck it's going on: Yikong DB7 1/7 scale desert truck. Took a few months to get it from China, but it's a freakin' beast. Tires are super hard. They are similar in size to the JConcepts 2.2 tires (and similar crawler tires that are 145-ish mm in diameter. Wheel hexes are 12mm and use a pin, unfortunately.

Hacked foams—one can see I cut a conical/ vortex shape into the foams.

Tires hacked, too. Maybe not a shark attack, but not great.

 

[slick2500]

These are the tires: https://www.amainhobbies.com/jconcepts-landmines-2.2-rock-crawler-tires-2-green-jco4050-02/p1478018. The dimensions of the foam are 2.2 x 5.79 inches.

I did find 3d printed inserts, but again, they are designed for a 2.2 wheel. https://www.ebay.com/itm/385671504688.

This is the truck it's going on: Yikong DB7 1/7 scale desert truck. Took a few months to get it from China, but it's a freakin' beast. Tires are super hard. They are similar in size to the JConcepts 2.2 tires (and similar crawler tires that are 145-ish mm in diameter. Wheel hexes are 12mm and use a pin, unfortunately.

View attachment 345751

Hacked foams—one can see I cut a conical/ vortex shape into the foams.

View attachment 345752

Tires hacked, too. Maybe not a shark attack, but not great.

View attachment 345753

What do you mean the tires are 12mm hex but use a pin?

 

[obessedwithrc]

Sorry, I meant that it uses a 17mm hex, similar to the Traxxas UDR, with an M5 stub axle that mounts with an M5 locknut instead of the typical 1/8th scale setup. Unlike the Hammer Rey U4 which fits a 2.2 tire, the Yikong TB7 is similar to the UDR in that it uses 2.2/ 3.0 short course style wheels.

UDR hexes:

What I am doing is cutting 2.2 tires on the backside, enlarging it to 3.0 inches so that I can use an SCT-style wheel with the JConcepts 2.2 Landmines. I'm going to use a beadlock wheel + glue to secure the tire to the wheel.

JConcepts does make Landmines for the Mojave that I could make work on the truck, but they are slightly too small in diameter, similar to other Mojave/ UDR wheel and tire combos. It seems like the 2.2 U4 tire option is my only choice.

I'm using the 2.2/ 3.0 Pro-Line SCT beadlocks, but may use a 2.2/ 3.0 Vitavon or RC4WD beadlock wheel if they look good on the truck.

Pro-Line Raid Beadlocks w/ scale hardware from LockedUp RC.

Or I'll use these:

Vitavon beadlocks on BFG Pro-line tire (tires taller than typical SCT tires).

RC4WD on Traxxas Raptor R tire (going on my Raptor R that I'm building) (tires taller than typical SCT tires).

RC4WD beadlocks on a Kyosho Toyota TRD short course truck w/ HB Racing Rodeoo tires (tires taller than typical SCT tires).

 

[Tex Koder]

Rough draft >
Wheel FOAM Insert Cutting Guide


It'll be a two piece design.
Here's the base half.

How thick is that foam?

How soft is it?
Can you flatten it out, completely flat?

 

[obessedwithrc]

@Tex Koder - it's 53.5mm in width. It's a medium foam (not rock hard, but not soft). Pretty sure these foams are meant for heavy trucks. Using light pressure, I can squeeze the foams down to 20mm in width using calipers. With moderate pressure, I can get them to 10mm. With "He-Man" pressure, I can get the foams down to 5mm. I think 10mm would probably work best. Any more and the foams could deform in the center. Any less, and it would be hard to keep a straight cut.

 

[Tex Koder]

@Tex Koder - it's 53.5mm in width. It's a medium foam (not rock hard, but not soft). Pretty sure these foams are meant for heavy trucks. Using light pressure, I can squeeze the foams down to 20mm in width using calipers. With moderate pressure, I can get them to 10mm. With "He-Man" pressure, I can get the foams down to 5mm. I think 10mm would probably work best. Any more and the foams could deform in the center. Any less, and it would be hard to keep a straight cut.

That's what I needed to know.

I'll get the top half finished soon...

 

[obessedwithrc]

Right on mate. Love the people in this forum! Insanely helpful.

 

[Tex Koder]

@Tex Koder - it's 53.5mm in width. It's a medium foam (not rock hard, but not soft). Pretty sure these foams are meant for heavy trucks. Using light pressure, I can squeeze the foams down to 20mm in width using calipers. With moderate pressure, I can get them to 10mm. With "He-Man" pressure, I can get the foams down to 5mm. I think 10mm would probably work best. Any more and the foams could deform in the center. Any less, and it would be hard to keep a straight cut.

Drafts completed.

Based on your Foam specs -

Upper Cutting Template

Place your wheel foam in base.
It'll keep it centered when you mount the Upper half.
Push down until it locks down -it'll give you a perfectly even 10mm height all around.

Using a X-Acto knife, you slice straight down against the outer edge of the center "donut" - there is a 0.5mm cut-groove in the base to help guide your cut around the center portion of the foam.
(There are bevels on the underside of the 3 spokes to allow for you to get a tight reach to continue your cut ,completely around.)

Once done, left the Upper half and remove your foam insert. And, pop out the center piece.

Let me know if you have any questions.

 

[obessedwithrc]

Holy sh*t. You are a freakin' genius, @Tex Koder. Let me know what I can pay you to print and ship (with a fat tip, of course). Happy to pay for STL files as well, if that's easier for you. I don't have a 3d printer, but I can send it to Shapeways, even though they cost an arm and a leg. I'd rather than $$ to go to you. Haha.

 

[Tex Koder]

Holy sh*t. You are a freakin' genius, @Tex Koder. Let me know what I can pay you to print and ship (with a fat tip, of course). Happy to pay for STL files as well, if that's easier for you. I don't have a 3d printer, but I can send it to Shapeways, even though they cost an arm and a leg. I'd rather than $$ to go to you. Haha.

Will do.
I'll add it to the print queue.

There's a slight line ahead of you..
Will let you know once yours parts get loaded.

 

[obessedwithrc]

No worries/ rush. I'm grateful for the help!