WesWorld

http://63.99.108.76/forums/index.php?showtopic=21200

I found this program for designing tanks, similar to SS but in excel format. Its a bit of a pain to use at the moment but will probably get better with time.

New version is now up at http://home.comcast.net/~mksheppard. I haven't really looked at it for all the changes, but I've already spotted that now skirt armor has a default effectiveness against HEAT rounds.

OK, I've now had a chance to run through the new version of TankSharp (0.71). Fairly major changes from the previous version (0.6), the new version has added a lot of pick lists where the older version had spots for the user to enter a number (where the values for that number weren't immediately apparent). A large number of materials are now available as choices for armor (though most are more modern than the time period we're concerned with), allowing a user to choose cast, rolled, perforated or hardened steel (for instance). The choice has effects: some choices are denser than others, others are harder, and some are cheaper and easier to produce (though TankSharp doesn't show that).

Notes:
TankSharp 0.6 calculated track area based on both tracks, so a user would put in the effective width of both tracks. TankSharp 0.71 calculates track area based on a single track, so divide your entry from TankSharp 0.6 in half for 0.71.

Also, for this period, remove the general armor modifiers that come in the spreadsheet (they're in the green box at the bottom of each armor facing section in the hull and turret design sections).

Some suggestions for tweaking TankSharp for our period (based on a design to duplicate the M-18 Hellcat):

1 - change the formula in the Drivetrain sheet for the volume of a road wheel to: =((B10/2)*Pie*B13)*0.0168 (Essentially dropping 1 extra 0 behind the decimal point). This will increase the weight of the vehicles road wheels, the original value is WAY too low.

2 - Keep length of recoil in medium caliber tank guns (lke the historical US 3", the German 75mm/L48, etc) short, around 4-5". And don't use highly effective muzzle brakes, they're in their infancy in this period. A 4" recoil distance and a 10% efficient muzzle brake worked well on my M-18 copy. For guns less powerful than those, don't use muzzle brakes at all.

3 - Pay attention to the Minimum Transmission Weight Needed on the Engine sheet, especially if you have a powerful engine for your vehicle size. Be sure to exceed it on the Manual Transmission Weight Input line just below it, unless you LIKE the idea of the transmission always breaking down.

4 - On the Drivetrain sheet, for Type of Track use the next higher entry for your vehicle (ie, if you're building a 17 ton tank destroyer, choose 3-40 ton Vehicle Conventional).

I'm not so sure on the armament issue. The 47mm used in Italian tanks has a recoil of 340-630mm (force can be altered), other figures I've found for larger guns are between 300mm and 1000mm depending on calibre. The longer recoil obviously adds quite a lot to the length of the turret. With no muzzle brake, Tanksharp gives a weight of 656kg which is obviously far too high when you consider that the weight of the gun in a carriage with wheels etc. is 316kg. I played with the muzzle brake % to get down to a more sensible 250kg, which is still probably conservative.

I'm still using Tanksharp 0.4 as its easier for specifying your own bits, i.e. taking the figure for the T-72 transmission and adding weight to it to better reflect the period. You'll want to check the "track width" box and change it to /10 instead of /100

I'll have a better big through the spreadsheet and see what else is wrong.

On the road wheel volume you want radius^2 * Pi * thickness * 0.4 or so.

I'm not necessarily trying to get the weight of the gun correct, I'm more trying to get the weight of the vehicle correct. Yes, with the short recoil distance, the weight of the gun (actually the recoil system) will be more than it historically should be, but the weight of the vehicle ends up correct. I expect you can get the same result by boosting the transmission weight, but I don't know that that's any better.

No, you DEFINITELY don't want to use * 0.4 in the volume of the road wheel formula, that says that the road wheels are 40% solid. On the M-18 sim I did, that meant that each of the 10 65cm roadwheels I had would weigh 3,050 kg, with a total road wheel weight of 30717 kg (on a vehicle that weighed only 17,700 kg total historically). The 0.0168 number I gave results in a weight per road wheel of 128.08 kg.

I suspect part of the problem is that there's no "vehicle structure" tonnage required: the weight is the sum total of the parts that are modeled, there's no tonnage used up on internal structure to hold all those pieces in place. No weight for engine brackets, drive sprockets, return rollers, idlers, internal framing, etc.

Hmmmm. Looking into the issue of structural weight, I came up with something. It's rough, but it might get us closer to where we want to be.

Using TS 0.71, insert a new line after Road Wheel Weight on the Tracked Print Sheet page, call it Structure Weight if you like. In cell B27, insert the following formula: =(B15*0.5)+(B18*0.5)+(B18*0.5)+(B22*0.5)+(B26*0.25). This corresponds to an additional structure weight of 50% of the vehicles armor, engine, and transmission weights, and 25% extra for the vehicles running gear (idler, drive sprocket, return rollers, etc).

Adding this line allowed me to get the M-18 to be right on weight wise with a pretty reasonable gun weight (with recoil gear) of 1050 kg (with a 20% efficient muzzle brake and a 800mm recoil stroke).

The above worked for the M-18, but not for other, more heavily armored, vehicles (or vehicles that had similar armor but were slower). So, more tinkering has resulted in the following:

Using TS 0.71, insert a new line after Road Wheel Weight on the Tracked Print Sheet page, call it Structure Weight if you like. In cell B27, insert the following formula: =(B15*0.25)+(B18*0.5)+(B22*0.5)+(B26*0.25)+(B16*0.25)+(B24*0.25)

This corresponds to an additional structure weight of 50% of the vehicles engine and transmission weights, and 25% extra for the vehicles armor, armament, running gear (idler, drive sprocket, return rollers, etc), and suspension. This works quite well for the M-18, the Panzer II, and the Panzer III.