Half Track build

[MadInventor]

Great to see some progress on this one, it's still my favourite build of yours.

I've been banging my head against the grapple skidder build for a while now, so thought I would take a short break from it and try to progress this a little. Will hopefully get the top front plate done along with the 2 side plates in the next couple of weeks. After that it will be some more thinking time to figure out what to do with the front end before pressing on. I found that the 4274 motor is too long to fit under the rear hull, but that doesn't mean I can't put a mildly hot brushless system in it. And the 3S battery still fits in at the moment

[MadInventor]

Got 2 more body panels done:

Upper front deck:

Side panel:

This side panel is a bit shorter than intended as I got the first angled cut wrong, but I'm going to cover the lower hull panels in zimmerit, so I don't think it a patch is going to notice.

Fit is not that good at the back as it was a bit of guesswork, but the 'No Nails' zimmerit will cover it and hold it together well.

Starting to look good, overall quite pleased with the panel fit.

Shocks are as high as the roof, so I definetly need to rethink the front end .....

[MadInventor]

Some more progress on the half track, I made a commanders cupola on the lathe this week, and added a panther hatch I had left over from Jagdpanther build:

I made the handle from a small piece of copper mains electric cable.

I've also now got the rear hull glued and bolted together, and added zimmerit to 2 of the body panels, as well as a few detail items.

Large panel gap at the back end was covered well with the 'liquid nails' .

I've also glued in the front upper hull plate, and added a drivers escape hatch, from a king tiger sprue:

I also repaired the panel I cut off short, the join gap will be covered with zimmerit.

This pic shows the slightly lowered chassis rails. I may need to lower them further than this yet

[Vrdetailing]

Loving it carry on commander

[SteveU30]

Loving that this build is marching on now (excuse the military pun), the scale details are a great addition!

[MadInventor]

I'm trying to decide now what to do about the front chassis:

I have a problem in that the cantilever shocks are almost at the height of the roof, and I need to slope a bonnet down to the front of the vehicle.

I thinking about lowering the chassis rails at the front to the same level as the rear rails, so that the front of the shell will look sensible, but this then leaves no room for the solid front axle under the chassis rails. I'm thinking that some FAV wheels and tyres might look ok on the front, and are 20mm less diameter than the F350 wheels, so would lower the front axle a little. However, have looked on evilbay, FAV wheels and tires are v expensive, so I'm wondering if anyone can suggest a cheaper alternative.

Grasshopper wheels are cheap at the moment, will FAV tires fit ok on these without coming off or require gluing. Also, what is the grip / wear like on FAV tires, the half track drives very well at the moment with the F350 tires on the front. I'm thinking I want to run this on sand, and am wondering if the FAV tyres will just sink in, as they are a lot narrower than the F350 tires. PS I know grasshopper wheels are a different fitment to the F350 items, but it's not a major problem if I have to change the front axle.

I'm also in 2 minds whether to stick with the 4 links and the solid axle, or whether to lower the front chassis rails and try and attach double wishbones for independent front suspension, and use some TT-01 shocks mounted upright without using cantilevers at all, but this might be difficult to build the front of the bodyshell around. Trailing arms as on the front of the FAV / wild one might work, but won't look very scale.

I could also go for a shaved down front axle, fit the servo in the chassis, and go for leaf springs on the front.

arrgghhh !

Thanks,

[SteveU30]

Looking at that side shot the first thing that sprang to mind was that the wheels are too large in diameter (that was before I read you were thinking of changing them). How about using Brat wheels and tyres? They are smaller diameter but wider than GH/FAV wheels so best of both worlds.

Suspension wise, my vote is to put leaf springs on. I don't know what half tracks would have run on in real life but leaf springs 'feels' right in my head.

[MadInventor]

I thought about the brat wheels and tyres too, as I have a some on the back of my forestry trailer. When I measured the diameter of them, they are only about 10mm small diameter than the F350 tires. The FAV tirs are 20mm smaller diameter. The Brat tires would probably be enogh to make the front look a bit more sensible, but wouldn't drop the front axle that much (Around 5mm). It looks however, that I am probably going to have to ditch the existing front axle and fit the servo into the chassis. I think the thing to do is take a couple of wheels off the trailer and mock it up to what it's going to look like. I will also try and find a picture of the front suspension of the real thing for comparison. More pictures tonight

[speedy_w_beans]

Here's a thought.

Flip the two front cantilevers so the dampers are angled down instead of up; you already have clearance with the chassis rails so that's not a problem. Now the springs will need to be in tension instead of compession, but that can be addressed in a few ways.

Switch to threaded aluminum shock bodies and reverse the adjuster collar so the spring won't pull away. You might have to notch the collar to let the coil pass by. For the lower spring retainer, you could probably machine new one-piece damper eyelets/spring retainers. You might have to cut one coil off the spring, but that could be done at the eyelet/retainer end. Add O-rings to the damper shafts both inside and outside the damper bodies to limit travel.

Now when the axle absorbs a bump from the road, the springs and dampers will actually extend instead of compressing. The spring rate and damping dynamics are the same regardless of whether you operate them in compression or tension.

EDIT: Note that cutting a coil spring changes the spring rate. Another option is to go with soft touring car springs; they are shorter than buggy springs and you'll have a few extra coils at each end to provide a good connection. Also, if you find the cantilever is still a problem with the sloping bonnet, you could always make some mounting plates to move the cantilever lower than the chassis rail.

[Percymon]

Or use a bracket to lower the cantilevers such that the damper runs along the chassis rail ?

[speedy_w_beans]

Or use a bracket to lower the cantilevers such that the damper runs along the chassis rail ?

Even better!!!!

[MadInventor]

I'm thinking the bracket to lower the cantilever is the way forward, although I would still like to get the chassis rails a bit lower.

Here's a mock up of what it will look like with brat wheels:

This diameter tire looks a bit more sensible

If I lower the chassis to the same level as the rear rails, there won't be much room under the chassis rail (about 10mm from rail to axle centre:

However, I prefer the diameter of the brat tire to the F350 item, but I also found these bad boys on ebay:

which are the same diameter near as the brat tires (84mm), but are narrower and fit on 1/14 truck wheels. I can get a set for a reasonable price, and I think the truck wheels painted matt green will look a bit more scale than the brat items as well. The only problem is that they are described as 'super hard' and I suspect that they may not grip very well. Something to ponder on .......

Also plodded on with a bit more on the shell today:

Added C hooks to the rear hull to hide the allen bolts:

Completed the vents on top of the hull:

Glued on the final piece of body armour for the rear portion of the body. This new panel is what the drivers viewhole will be attached to, and what the bonnet will fold down onto.

[biggamehunter]

glad to see this moving again , great job on the bodyshell ! theres some great looking steel crawler wheels on the bay cheap , but they are 1.9" so probably a but big , loving the no nails zimmer finish and your turning of ancillieries is outstanding , still watching with interest great work

[MadInventor]

Finally got around to making some caps for the idler wheels over the last couple of days (putting off doing the chassis mods to the front end ). Now I've got these done I can some paint on the aluminium wheels I made. Shame to cover them up really, but it will look better with paint on

[speedy_w_beans]

Those look like brake discs in the first photo!

[Skottoman]

Wow, you really earn your screen name with each build you do.

Love your use of liquid nails as texture. Brilliant!

While I love the custom metal work, I can't wait to see this painted!
CHeers,

Skottoman

[MadInventor]

Splashed a bit of paint on today, put the base colour on the wheels and primered the bodyshell. Looks a bit better, but I ran out of dark green so couldn't complete it. It's also possible to see the hub caps I fitted on the rear idler wheels. The last body panel I thought I had fitted fell off when I touched it, so I will need to re-stick it on with something flexible like bathroom silicone. I also ordered a pair of all terrain 1/14 truck tires, as I was struggling to find a pair of brat wheels. I'll need to make a pair of front wheels for the tires on the lathe, these will probably be solid aluminium, have to wait and see when the tires get here.

[stu22]

If I lower the chassis to the same level as the rear rails, there won't be much room under the chassis rail (about 10mm from rail to axle centre:

Have you considered lowering the front rails and arching them over the axel? If you look at an old Jeep frame you can see they did it to give some more clearance for the suspension. With the materials you're using you could probably use the lower profile of the stock you're using to lower things even further and I doubt strength will be an issue.

Would it be possible to run the front shocks on the inside of the frame rails? Looking at it, it looks like it would be possible to flip the cantilever over so the compression on the shock would go forward, extend the mounting point of the shock farther into the frame, and mount the shocks over the axel. There would probably still be some clearance issues to work out but it's an idea.

[MadInventor]

Done a bit of a rebuild on this on the weekend. After much thought, I made 2 new rear chassis rails that extend further from the chassis. This will give me something to mount the lower part of the front hull onto, as well as making it easy to fit a battery holder and move the attachment point for the front chassis forward. I've also made the battery holders but the 3s battery is a bit high for the bodyshell so have got a little bit of a rethink going on. I thought about stu22's idea (thanks Stu) about using the chassis rails on their side to increase clearance, good idea but the aluminium bends in that plane, so I am going to make the forward chassis rails out of 12mm box section steel. This is a lot stiffer, and now I've extended the rear chassis rails forward I shouldn't need long runs of it which might add to the weight, and it shaves 8mm off the height of the chassis rails. I've also decided to mount the servo on the chassis and use a pivot like on the high lift steering to operate the steering on the axle, this means I can make the axle a lot thinner which will also increase clearance above it.

New, longer chassis rails, and battery holder plates. Made them out of plastic as there is less chance of a short. The diagonal holes in the chassis rail at the front are to bolt the mounting plates for the lower frontal armor, which will act as a skid plate to protect the drive axle and help to keep muck out of the rear hull when running. I've also screwed plastic block into the chassis rails below the gearbox mount points so that I can use self tappers to hold the gearbox in, as it was very fiddly trying to get the nuts on the bottom of the bolts and the chassis aluminium is too thin to take a thread.

New tires appeared in the post today as well. I think they will look quite scale and am pleased with them.

[stu22]

Was poking around the net and found this page with some picts of an Sdkfz 251 without the front armor on it.

http://www.achtungpanzer.com/mittlere-schtzenpanzerwagen-sdkfz251-ausf-d-sdkfz2519-stummel.htm

Looking at the front, there appears to be a traverse leaf spring for the front.

[MadInventor]

Was poking around the net and found this page with some picts of an Sdkfz 251 without the front armor on it.

http://www.achtungpanzer.com/mittlere-schtzenpanzerwagen-sdkfz251-ausf-d-sdkfz2519-stummel.htm

Looking at the front, there appears to be a traverse leaf spring for the front.

I've seen this also, but thinking about it, if I used, say a king hauler leaf spring, how would you cope with the expansion in length of the spring as it is compressed ? Fixed mount points will prevent the spring from working, and double spring hangers will allow the axle to float left and right below it. A single spring hanger on one side will cause the axle to move to one side as the spring is compressed (Bump steer !!!) Also, considering I want this to go at a rate of knots, I think I'm going to need some damping on the front, as there is none at all on the track idler wheels at the back. .

I had to abandon turning my own front wheels as I couldn't get the tires to sit tidily on the wheels, so I have ordered a pair of king hauler wheels for the front. Not the most scale, but will enable me to rebuild the front end, and then I can perhaps have another go at making my own wheels once I have an original to take the dimensions from.

I've still got a couple of ideas up my sleeve for the front end, once my wheels turn up I can start on remaking the front axle.

[MadInventor]

I've now got the axle guard done. This is what would have been the lower glacis plate if I was just building a tank. It's what the bodywork for the engine compartment will butt up to.

Still got to make the side plates and lower plate to enclose it all in, but you get the picture.

[speedy_w_beans]

I'm enjoying all the photos, especially the first one in the February 9 post.

[MadInventor]

I'm enjoying all the photos, especially the first one in the February 9 post.

I'm very much 'A picture speaks a thousand words'

Speaking of which:

Got the front chassis rails made and refitted today:

Mounting plate detail. There's 40mm between the new rails, enough space to mount a servo in there.

Height is now better in relation to the rear bodyshell. If I start the bonnet half way up the black plate, there should be a reasonable amount of slope.

Just got to figure out how to work the front axle and suspension now

[mongoose1983]

Looks pretty good!