The Craftmans Shop > Radio Control Models
1/16 Scale RC Truck parts
ddmckee54:
I've been keeping an eye on Yuri's work for a number of years now. The last time I checked, he'd found out that the Igaging EZ-View Plus scales use a different protocol than their Digi-Mag scales did. He was working on an interface but it wasn't ready yet.
ddmckee54:
Further development on the is on hold for a week or so. The motor/2-speed gearbox, that I initially wanted to power the model with, uses a single 370 sized motor and has 3mm output shafts. While the 370 sized motor MIGHT have been up to the task, I don't think the 3mm output shafts would have been - since all of the differentials have 5mm input shafts.
I've got an LDRC LD1201 Unimog replacement motor/gearbox ordered. It uses a pair of 370 size motors driving a 2-speed gearbox with 5mm output shafts. One of the outputs looks to be centered, and the other appears to be offset to the side. If it is offset then I'll have to slide the pumpkin to one side on the front and rear housings for my steer axle. Unless I can find some drawings on-line, I won't be able to do any more work on the steer axle until I can get some measurements from the gearbox.
ddmckee54:
The motors/gearbox/transfer case arrived today, now I'll start 3D modeling it. That way I can use that model to design the offset I'll need for the pumpkin in my steer axle. I'll also have that model for use in designing the parts for the future conversions. The output shafts are 4mm, not the 5mm I had hoped for, but they can easily be bushed up to the 5mm needed by the differentials.
I was worried that there wouldn't be enough room for the Universal joint to the front axle. The dimensions for the drive shafts I'm looking at say they're 12mm in diameter. The only way I could get a measurement to the obstruction was by measuring across the shaft to the obstruction, and that distance was 8,55mm. Since it's a 4mm shaft, that means the obstruction is 6.55mm away from the center. The drive shaft needs 6mm, so I SHOULD have at least a half mm of clearance. And clearance is clearance Clarence.
It also looks like I'll need to make custom drive pins/set screws for the drive shafts, but that'll be nothing more than turning down some 4mm set screws to fit. I'd better get some 4mm set screws on order so I've got something to work with. It's real IFFY that the local hardware store would have any. I have trouble finding anything smaller than 6-32 in Imperial and 5mm in Metric.
Don
ddmckee54:
Between a late night last night and some more time this morning I got the motors/gearbox/transfer case modeled. I measured the wheelbase between the front axle and the center axle in the MAN mixer and extended my frame rails accordingly. I dropped the motor unit into the assembly model and got it positioned about where it will live. The assembly model now looks like this.
This thing is starting to look more like a truck, and less like a clown car. The frame rails are 335mm long now which is probably about right for a 1/16 scale cab-over.
I COULD move the front diff's pumpkin 18.5mm to the passenger's side, which would get the transfer case output shaft and the differential's input shaft lined up side to side. But, if I do that then the pumpkin is going to be crowding into the area that the knuckle pivot needs to live. So I'm only going to slide it over 10mm. The drive shaft angles will be a little harsher, but it's not like I trying to design these for thousands of miles of useful life.
ddmckee54:
OK, a couple of minor speed-bumps, but nothing that Ebay and a credit card can't handle.
Speed-bump #1 - Most of the drive shafts I've found have 5mm bores or 6.2mm bores. The WLToys axles have 5mm input shafts and the shafts with a 5mm bore are a better fit to the LD1201 transfer case. But the LD1201 has 4mm output shafts. No problem, I'll just cut a piece of 4x5mm tubing and glue that into one end of the drive shaft. "Cept that I ain't got no 4x5 tubing, I've got 3x4 and 3x5 - but no 4x5.
Speed-bump #2 - Drive shaft lengths. I can't really find the drive shaft lengths I need. My last revision of the 3D model for the suspension/chassis put all the axle spacing's in their correct positions for the upcoming cement mixer conversion. I also centered the gearbox so that the front and rear drive shafts can be interchangeable. This leaves me with a nominal drive shaft length of 46-ish mm. Since the transfer case output shafts are 2 different lengths, 6mm and 7mm, I'm using the 7mm length to determine the minimum and maximum drive shaft lengths. I need to collapse my 46mm nominal drive shaft about 7mm in order to be able to remove the drive shaft - without needing to remove other bits of the truck anyway. I also need to allow for suspension droop, which won't be much since this is a cement mixer - not a rock crawler. But I need to allow for some, so I'll use 7mm there too. Bottom line - I need the front and rear drive shafts to be from 39-53-ish mm in length. It can be more than 53mm, but no less. The drive shaft from the center axle to the rear axle is worse, it needs to be from 33-44mm in length. These are the drive shafts that I like the best. https://www.ebay.com/itm/375169557748
But....The shortest length is 60-77mm, I've got 3 of them on order. On the plus side, they use an internal/external spline for the extension instead if a square drive or a pin in slot setup. The external splines are full length, they are easier to cut so that makes sense. The internal splines are not easy to do at this size. That difficulty goes up as the spline length increases, there's not that much room in the hole to begin with and the chips HAVE to go somewhere. My guess is that the splines are only a few mm in length, the rest of the hole will be counter-bored to the major diameter of the splines - if not larger. My current plan is to cut a big enough chunk out of the middle of the female half that the length of the stack-up equals my minimum drive shaft length. I've got some 3/8" OD aluminum tubing that I'll use as a reinforcing sleeve and glue the cut parts into it. Then I cut the male splines off just enough to allow the drive shaft to fully collapse. And Bob's you uncle - I hope. It worked for the axle shafts, should work here too. We'll find out. I also ordered 2 of these. https://www.ebay.com/itm/314228515981 To see if I can cut them shorter than the others for the center to rear axle shaft.
If I get REALLY lucky, and the internal splines go full depth, then all I have to do is cut things to length. (And if you believe that's gonna happen... Well, I got some bottom land in Florida I'll sell you - it's REAL close to the river.)
Don
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