How does everyone get their tyres to look like they have some weight in them? ie sidewall bulge.
I’ve tried boiling water. Candles etc etc etc. But the best I can do is melt the bottom without distorting the wheel rim.
The below image is the best I can do without help from the brains trust. (It’s a wheel/tyre from the Thunder Scammell kit. One on the left is for the kit. The one on the right is one of the spares provided in the kit). It has some sidewall bulge but to get it it flattened the bottom too much.
That’s a challenge. I’ve seen a technique for making convincing -looking flat tires, but not sagged tires. Best suggestion I can offer is resin after-markets.
That is a good reason why the aftermarket for weighted tires (both aircraft and armor) has many players in it. To get it right, it almost needs to be cast or molded that way. I am sure that some builders have been successful, but I would say that the majority tried and failed.
Do military vehicle tires even have bulge?
Not usually. It is a way overdone artistic feature.
I see no bulging/sagging/flat tires at all.
I will often grind a small flat in the bottom of the resin molded tire but that is the extent of it.
And of course I don’t try anything like that with the molded rubber tires though I do my best to remove the mold lines down the center of the tread.
As Gino writes, hardly noticeable in 1/35th scale.
I would just sand down the contact surface where the tire touches the “ground” a little.
Some vehicles have tire/tyre pressure regulation systems and those would usually have a noticeable bulge when driving over sand or other soft surfaces.
The contact surface of a medium size civilian car is in the rough ballpark of the size of a palm and that is a small spot in 1/35th scale …
If you want a bit of a bulge in the lower sidewall, and if you have vinyl tyres, and if the hub is sturdy enough, one option is to screw it. Attach tyre to hub, put a small countersunk screw through the tread, and screw it into the hub just enough to pull the two together. The head of the screw should act as a flat and the natural properties of the vinyl will make it bulge to either side. You can even adjust the screw to suit. And this method takes no heat, no chemicals or adhesives that would eat the vinyl, and no resin. I only wish I’d found out about it before I shelled out all that money on aftermarket tyres.
Narrower tyres (eg most WW2 vehicles) may not suit this method, although you might find slim enough screws in the jewellery trade.
Here in Australia its common to let some air out of the tyres when going off road. So I assumed they would let some air out even during WW2 to get more traction in the field.
BGT - you make a fair point, however unlike many German vehicles the Allies would have little way to restore air pressure later so I doubt they would be doing this very much unless in an emergency. Also once they got back of the hard pack, deflated tires use more gas and wear out faster.
Just a thought . . .
The newer generation of run flats are not self sealing but actually a honeycomb design internally. I got a chance years ago to try out a set Bridgestone was developing and they were amazing. No bulge either.
I wish somebody would write to DEF and strike them with the revelation that military tires do not bulge! DEF makes great tires but I wish they had no bulge in them.
If you see a military tire with a bulge, then the driver hasn’t kept up his PMCS and properly inflated the tire.
Someone posted an article about creating sagging tires before, not in the position to search for it. Basically you use a pin. You drill a small hole in the hub to hold the pin and then push the pin in from the bottom and superglue it into the hub so it creates the sag. Cut the pin to length as needed before super gluing it.
This is assuming you are using the vinyl tires that usually come standard.
All pneumatic tires will both flatten and bulge under load. It’s physically impossible not to. (Even all-steel railroad wheels flatten and bulge, as does the rail.) The bulging on most “loaded” aftermarket tire sets is excessive, however.
The amount of tire bulging is dependent on the tire pressure and the tire construction. As somebody mentioned above inflation pressure was lowered for soft terrain to increase the size of the contact patch. This will increase bulging as well. (Ex. the DUKW) These are called Military Desert tires in the US. During WW II tires used a bias ply construction that did not bulge much under load. I believe that many current military tires (and almost all car tires) use a radial ply construction that allows greater bulging. (When radials were first introduced for cars there were many problems from people trying to inflate the tires to the point where the sidewall bulge disappeared.) In the US Army many vehicles also used Combat construction which had a very heavy wall to give some run-flat capability. These tires were particularly stiff.
A rough ranking of the amount of bulging evident (most to least)
Whatever method you use, it pays to research what’s appropriate for the era and tire.
Research: photos of the prototype vehicle in similar load conditions (empty or full load) as the model will be useful.
Robin no particular prototype.
Im currently building a Thunder models Scammell. It comes with many spare wheels and tyres. Out of interest i thought i would see if i could get a bulge in the sidewall. Just a part of the learning curve!
Ive concluded that getting the plastic soft is all but impossible without going too far and really melting them.
The wheels are a part of the tyres so distorting the wheel becomes another issue.
Ah building up the sidewalls will lose the tyre detail! I thought of that.