What is considered proper running weight?

[BarryC]

Hi all,

I am working towards trying to properly weight my HL M1A1 Abrams build. I am talking about both overall weight and weight on suspension springs. I found that a very unmanageable weight of about 20 pounds was needed just to get the springs to suspend the weight. Meaning that the weight was "hovering" on the springs and any force on suspension arms is absorbed by the spring and not transmitted into the body until the spring bottoms out. I am quite certain that the suspension system was never designed to handle that amount of weight. I can structurally reinforce the hull but not the plastic mounting points for the suspension arms I mean I could but might as well build a complete metal lower hull. I am afraid the mounts will not survive very long under that type of weight!

I know that the metal tracks and wheels will add their total weight to the overall weight but not to the weight on the suspension springs; in the case of the Abrams' running gear this means that the Idlers their axle along with the return roller and sprockets and that portion of the track not in contact with the ground will be included in both overall and suspension weight. Of course the overall weight will also include everything mounted anywhere above the suspension arm attach points. However the road wheels, suspension arms and track in contact with the ground only affect overall weight so the bulk of the "metal" running gear weight is not on the suspension.

So my questions are:
1. What is your "overall" target weight?
2. What is the weight you target for the "suspension" system?

I believe proper suspension weight is critical to realistic running appearance especially when maneuvering over uneven terrain. It is a tank after all and should not "flop" around but maneuver smoothly. I hope I am making sense; what are you thoughts?

Thanks for listening,
Barry

[Tankbear]

Hi Barry,

I sort of get what your trying to achieve but haven't a clue how to work out the correct tension of the road wheel suspension.

I think as there is limited number of springs which will fit the tank it be a little trial and error to find the right setup. Also you might find that the front and rear road wheels need more tension than the middle ones otherwise track tension will pull them up during turns etc.

Ian

[Del]

I think your just going to have to use trial and error on this one,you could I suppose get the weight of all the real parts and scale them down but I think you may struggle finding the actual Spring rate the real thing uses.Then finding a spring/torsion bar with the exact scaled rate that fits in the tank may drive you insane lol.

[BarryC]

Hi Barry,

I sort of get what your trying to achieve but haven't a clue how to work out the correct tension of the road wheel suspension.

I think as there is limited number of springs which will fit the tank it be a little trial and error to find the right setup. Also you might find that the front and rear road wheels need more tension than the middle ones otherwise track tension will pull them up during turns etc.

Ian

Hi Ian, Thank you, I had not considered the affect of turns on the track tension.
I have both the stock springs as well as the "upgraded" springs. Do I assume the upgraded springs are stiffer than the stock springs?

Barry

[BarryC]

I think your just going to have to use trial and error on this one,you could I suppose get the weight of all the real parts and scale them down but I think you may struggle finding the actual Spring rate the real thing uses.Then finding a spring/torsion bar with the exact scaled rate that fits in the tank may drive you insane lol.

Hi Del,

Just quick math, if the Abrams weighs 70T then a 1/16 scale would weigh 8,750 pounds; would that be correct?

Barry

[ALPHA]

20 lbs sounds about good for a plastic hull....but to me surpasses what the initial design of the toy's capacity...which I would estimate to be more realistic at about 11lbs top....exceeding that puts a lot of stress on the stock structure already....you cut yours up...meaning your reinforcing will have to be very well thought out...almost to the point of redesigning a new hull...to get rid of all the stress ...while running and while servicing ....if you are going to take the build that far...investing in a more suitable metal bucket (hull) would be more feasible IMO...The one available will run you 6 to 1200 dollars US ...that option includes torsion suspension....It is something totally out of the question for me...but for a Hard Core Builder...probably the best route


ALPHA

[greengiant]

Mine is loaded with enough weight in the center and front to make the completed unit weigh right around 10 lbs. Other them adding some bracing to keep the hull sides from bowing in that has made it run over scale size obstacles much more realistically with the hull staying relatively level while the suspension works unlike when without the added weight the whole tank would jump up very toy like with little track contact with the ground.
I have the stock gearboxes, plastic tracks and have had no problems with them and the added weight on turns. Just had to get used to it acting more like the real tank on quick turns or steep grades where if the surface is soft or loose it will tend to dig in are slew to one side or the if a slow accent it tried.

[MichaelC]

I have both the stock springs as well as the "upgraded" springs. Do I assume the upgraded springs are stiffer than the stock springs?

Barry, if you have the factory standard spring set, and the upgraded spring set, you actually now have 4 settings you can try out. First of all the so called upgraded springs are usually a little stronger than the standard ones, but in additional to changing the spring, when you take out the swing arm in most Heng Long tanks, there is actually two position to insert the spring into the hull. The two position will also give you different tension on the spring. So 2 different springs and two different mount points will give you a total of four settings.

I would try the softest setting (i.e. factory spring in the low initial mount on the chassis) and go from there.

Track tension shouldn't really play a role. If you track tension is so tight that it is causing the swing arms to pull back it is probably too tight. The swing arms load should be solely determined by the weight of the tank itself. As to a "combat weight", I think it all depends on the component material of your tank and will require different spring settings to achieve similar weight simulation on the suspension. A full metal tank will be heavier and require more spring tension than an all plastic one, and somewhere in the middle would be the plastic tank with heavy metal components like tracks and roadwheels etc., all things being equal.

[BarryC]

Thanks guys, good suggestions all.

Excellent information on the springs Michael, I had noticed the two holes at each spring location but had not considered that that would give me an additional tension setting.
I will be using the HennTec Track Tensioner so hopefully I will be able to achieve the proper tension for the spring combination!

I have posted some pictures in my build thread of the bulkheads and structural reinforcement as well as some added weight.

Thanks to ALL
Barry

[silversurfer1947]

Regarding the scale weight, one has to consider the scale volume of the tank, which means reducing the weight by a factor of 16 for each dimension. On this basis, using an American ton of 2000lbs, the weight of the tank would be just over 34 lbs.