134 replies to this topic

[Pablo]

Tire trimming worked out fine, all four .56" OD and .41" width.

"Low-profile" for sure

 

 

The scale math seemed to work OK for the fronts - they look good, don't they?

I like the fact they are low profile and hard. So they stay.

 

Scale math for the rears didn't work - the widths are fine but the OD's are way too small.

Plus, I don't like the hardness of the low profiles. So, they are a no-go.

I'll strip the urethanes off them and install Wonder Rubber donuts at about .75 OD

 

[Steve Okeefe]

Pablo,

 

I think there may be some confusion going on here.  I've been watching your progress and I see where you've cut the tires to .560" OD.

 

.560" in 1/32 scale is 17.92 inches.  That's the approximate OD of the Halibrand wheels.

 

Checking the scale drawing of the real car (the drawing I sent you), I see the tires are about 27 inches in diameter.  In 1/32 scale that would be about .844".

 

If you're trying to stick to scale math, the tires should be about .844" (27/32" - slightly larger than 13/16").

 

[Pablo]

Concur with "confusion" 100%. I've admitted it from the beginning and that's why I asked so many questions.

Math doesn't lie but I'm obviously doing it wrong. The article you posted says the wheels on the 1/1 car were 16".

 

As per dc-65x post #47, I added 1.5" to the OD for the tires, 16 + 1.5 = 17.5

17.5 / 32 = .547

 

Where did I go wrong?

[Don Weaver]

He said the actual wheel​ size was about 1-1/2" larger than what the tire code would indicate, not the tire.  So 17.5" is the final wheel size and to that you would add the tire dimension you have calculated.  I think!

 

Don

[Pablo]

17.5 divided by 32 is .547.  Maybe my calculator is bad, or I can try an Abucus

You said "code" ?? Maybe I need a "de-coder ring" ?

 

Which leads me to another math mystery. The forefathers of D3/IRRA® decided on wheel sizes for 1/24 retro cars based on "scale".

So, why is it I'm building a little 1/32 car with a recommended 13/16 OD wheel, when 1/24 retro cars use the same size?

 

Confused on the math? Absolutely.

Confused on what I need to do for this car? Nope.

[dc-65x]

Hi Pablo,

 

Sorry for the confusion. Your .547" is "Korrect" for the wheel OD. You'd be using 13/16" diameter tires on your car if your trying to build an exact scale replica. That size on a D3 car is not exact scale.

[Steve Okeefe]

Pablo,

 

Here's a graphic I made to help illustrate what Rick is saying:

 

 

The wheel (a.k.a. "hub") is 16 inches in diameter (.500" in 1/32 scale).

 

Over the flanges on that 16 inch wheel measures 17.5 inches diameter (.547" in 1/32 scale).

 

The tire (a.k.a. "wheel" when it is mounted on the hub) is 26 inches in diameter (13/16" or .813" in 1/32 scale).

 

Regarding that Retro car math mystery, Rick is right: 13/16" or .813" diameter tires (wheels) on 1/24 scale cars (Retro or otherwise) are way undersized; nowhere near "scale".  The math: .813" x 24 = 19.5 inches.  About knee high for most of us.

 

Compare that to the prototype 26 inch tires on your STP Indy Turbine car, which would be 1.083" diameter in 1/24 scale.

 

Hope that helps! 

[Pablo]

OK now I see where I'm making my math mistake.

 

Rick said "The wheel size (16" in this case) refers to the diameter of the tire mounting surface of the wheel and the inside diameter of the tire measured across the tires mounting bead. The overall diameter of the wheel is actually about 1 1/2" larger."

 

I thought he meant add 1.5" for the TIRE. Turns out he meant the FLANGE is 1.5".

 

So the correct math is 26" OD / 32 = .8125

 

Thanks, I'm good now.

[dc-65x]

Thanks for the picture Steve.......it sure beats my babbling!        I've save it for future reference.

[Steve Okeefe]

At your service, sir!  Happy to help. 

 

Now, go build that STP Paxton Indy Turbine. 

[Martin]

Enjoying your build, Pablo; great to see this car built.

 

Did this car have a wing brake spoiler thingie at the rear? Never saw that in action, but it shows it in the drawing and you can see it laid flat in the photo.

 

Also couldn't but help notice the tires are taller than than the cars body for that scale look.

[tonyp]

The rear car had an air brake in the rear.


Sent from my iPhone using Tapatalk

[Jaeger Team]

That one

Attached Images

• 

[MG Brown]

Or this view if you prefer...

 

[tonyp]

I’m not sure they let it run with the air brake. I think a lot of “ slower” drivers complained they could not see when it popped up. I think they also had the same complaint about the exhaust


Sent from my iPhone using Tapatalk

[Pablo]

Same JK rims with Alpha Wonder Rubber, rough trimmed at .835" OD and .490" width.

Better?

 

 

I still want to use Paul Gage urethanes up front so I'll have to order another set.

Since I ground the others into pixie dust

 

Next question, should I go with 13/16" OD on all four, or go slightly smaller up front, maybe .790" OD?

.770? The 13/16's look really big to me up front........

 

[dc-65x]

Hi Pablo,

 

Just looking at some pictures of the race car the front and rears appear the same size.

 

 

 

Looking at this picture the tires seem narrower than on your model:

 

 

Maybe your tires don't look right to you on the front because they are a bit too wide???     I don't know.....I'm just eyeballing your model and some pictures. It would be interesting to pull some 3/8" wide or so tires out of your box of goodies and eyeball them next to the body front and rear.

[Ecurie Martini]

I believe the car was 4WD so same size tires all around would make sense.

 

EM

[Pablo]

Thanks Capt. Rick, and good point about the 4WD, Alan.

At this point, I'm thinking maybe (after another night of curing) giving the rears a final trim at .400" wide and .800" OD.

Then narrowing the front rims to .375" width, and once the new urethanes arrive, making them about .770" OD.

 

The more I try and over-think my wheels, it seems the more I gravitate towards Don Siegel's dimensions

 

If I change my plan one more time, people are going to re-nickname me "Capt. Waffle House"

[Pablo]

Jig motor arrived today

 

 

Mock up of .380" X .760" wheels. What do you think now?

 

 

[Tex]

those fronts look goooood.

[Pablo]

Thanks Tex, but I'm sure you know those Samson BB retro fronts were just to see how the size looked.

They would be nice wheels for the car but I don't feel this little guy needs the weight and complexity.

 

I think I have the wheels nailed down now

Fronts are urethanes, trimmed and trued to .380 X .785", coated with Mop n Glo.

Rears are Wonder Rubber .425 X .805

I found a set of Halibrand inserts and (one) mirror (second one is on order)

 

[Pablo]

Steve Okeefe .025" thick custom bracket, originally intended for retro, has found an important purpose here.

Unibit hogged the bushing hole to 15/32", axle holes to 3/16", and trimmed the top of the face.

.875 holes on RGeo jig blocks will make .805" rears clear .028".

Motor will angle down in the front, and need to be soldered to the bracket.

Oilites are Champion 3/32" with speed rings

 

[Pablo]

.039 wire bracing

 

 

[Pablo]

Motor mounting method is soldering the upper edge of the can to the bracket face.

Doing it this way adds bracket strength right where it needs it.

I tinned both surfaces with acid. DO NOT attempt to include the brass bushing gimbal in the party.

Avoid it at all costs - trust me. Solder the can to the bracket, not the gimbal.

I just tacked mine 'cuz it's just temporary - the actual motor can have a bead all the way across.

Tack, then check, then solder it home

 

 

Here is how she sets up, angled down, front of the endbell sits at ground zero