Need some advice on tires/wheels

[Krewmember]

Its nice to see someone else modeling a Gradall
What model of Gradall are you making? If its a modern one like the xl4100v or the xl5100v the spec sheets have the tire sizes for the 6x6 and 6x4 undercarriages, the 6x4 uses a 385/65R22.5 and the 6x6 uses a 425/65R22.5 so the rim is 22.5" at 1/12 scale that is 1.88" (47.63mm) so a 1.9 tire is close to scale.

Here are the tire dimensions in 1/12 scale just in case you need them.

385/65R22.5
Diameter: 3.52" (89.32mm)
Width: 1.27" (32.17mm)

425/65R22.5
Diameter: 3.69" (93.77mm)
Width: 1.39" (35.35mm)

The "MIL-SPEC ZXL 1.9" tire from rc4wd will be a little over sized even for the 425/65R22.5.

Hope this helps.



Shawn

[jgmick]

No specific model, more of a generic. I got intrigued by the telescoping boom structure and decided to see if I could make one. After some fooling around I got one built and working. It was sized as much by having to fit an actuator into the end of the inner boom to run the bucket dig/dump. (So much for scale). That is all done and working, so I'm moving on to the truck part.

I found some tires on eBay (China) that are 3.35" (80 mm dia.) x 0.78" (20mm) wide. Ordered those and am laying out the hub and drive structure. Need to get them in hand before I go too much farther.

I am going to need about 1-2 LB/tire load carrying capacity. That is where I bog down in trying to figure out what to do next. From what I can see here and elsewhere it looks like cutting donuts out of foam rubber as tire inserts gets the load carrying capacity up. I think I'm going to have to play with that some. (Yet another science project.)

As I said in my first post I do know that solid tires won't work. They just don't carry loads well in soft stuff. (sandbox). That is mostly where I need some coaching. I want to be able to drive around in beach sand to dig. (My kids love watching that action. Also a great way to get a crowd of adults around. ) Tracked vehicles work pretty good there, now I want to do it with tires.

Suggestions for tire to rim retention? Do they tend to spin the hubs in the tire when loaded and trying to drive? Also what types of foam to use as a fill donut?

[jgmick]

I tried this once before and it tanked but lets try again. Some pictures of the Gradall as far as I have gotten in the build.





More work needed on some covers for the electronics but this is all functional.