Let's Talk Tractor / Truck Pulling

[morrisey0]

My meet on Saturday got rained out, so I couldn't be nosey in the pits. I am getting the front design (well, the first draft) figured out, and have some parts printing.

The rear is where I am all over the place. Belts aren't going to work on the smaller "gears" as I can't get small sprockets for the belt size that I think I am going to need. Just not enough teeth on the sprocket. So, I am going to have to use gears or chains, at least on the motor pinion. I am also looking at planetary setups to see if anything that I could use. There is a Dewalt drill in my shop that I have a feeling is going to be in pieces soon. Heck, I don't even know if I want to go direct drive, or some sort of diff. I have a contact with loads of Traxxas stuff, and he is going to send me a Sledge complete rear assembly, and I am going to see if I think that will work.

But the main problem I have is that I still have no idea where I want to be FDR or rollout wise. From just looking at pics, the direct drive setups seem to be in the 20-90-20-90 ballpark, so I am just randomly shooting for around 20:1 now. But again, that is a pure guess.

I did get an old school Parma body, so got that covered.

Looking at the frame more, I think the SWB semi frame is too short, so I got to looking at my unfinished Grand Hauler. I painted the chassis and a bunch of plastic on that a color that I ended up regretting, and I just stopped working on it because I hated the color so much. Well, this was my excuse to finally tear it down and start over. I ordered some new rails, and am going to use the old ones on the puller. They are too long, but I will cut to length at the end.

[Phin]

You could go old school and use a Power Wheels transmission.

[Lowgear]

Yeah, they were sometimes used back in the day as a cheap alternative. I don't know how well they actually did but likely weren't amazing. I mean you're not going to be pulling any major weight with that kind of stuff but it works.

The first puller I ever owned was a sportsman with a wire frame chassis, C-cab body made from styrene, and a Power Wheels transmission.

[morrisey0]

While I wait on some rear end parts, I am just experimenting with other things. I realized quickly that most people build pullers on a simple aluminum plate, and there is a reason for this, it is simple! You want something here, you screw it down there. I thought I was making a mistake with the ladder frame c-channel, but now I am digging it a bit. I am just going over board on the printing stuff, and some may or may not hold up, but it is fun to play with for now. Now that I have a template for parts fitting within the ladder bars, I can just adapt that to whatever the design need is. So, now I have semi SFA mounts, steering servo mounts, lipo mount (which can be moved forward or back depending on weight need and screwed in), and a front weight mount within the chassis. The weight mount can hold pieces of 1/2 steel bar as needed, and will have a steel plate installed on top of it. And then a weight box (just an aluminum project box) will be mounted on top of that for added weight as needed.

[morrisey0]

So, for the rear pumpkin, the current plan as of 1936 EST 5/15/24 is to run a Traxxas Sledge differential, with a spool, and 7mm HSS driveshaft to 12mm hex couplers and aluminum Clod wheel adapters. This will probably change, but it is the current plan. I am thinking about just designing / printing a pumpkin case for the diff to directly fit into the chassis. I would love to run the driveshaft under the chassis rails, but I think that puts too much angle on the pinion. The current plan is to put a couple of holes in the chassis, and run the ds through it. This would also allow the highest strength case mounting to the chassis rails.

Who knows, I am just making this up as I go at this point.

Yep, too much reliance on printing, but I like the idea of trying it and seeing what breaks, and can I make it better. I wasn't planning on this being such a print-centric build, but I am growing into the idea of it. An aluminum ladder frame and a lot of plastic between it.

[RC10th]

Make sure your hitch is below the axle line

[Lowgear]

The hitch actually goes above the axle line these days. You want the front end to be pulled up, then weight is added to counterbalance the effect. This puts a lot more down pressure on the rear tires (fulcrum point) for increased traction.

In the sportsman class, the max allowed hitch height is 4 inches.

[morrisey0]

The hitch actually goes above the axle line these days. You want the front end to be pulled up, then weight is added to counterbalance the effect. This puts a lot more down pressure on the rear tires (fulcrum point) for increased traction.

In the sportsman class, the max allowed hitch height is 4 inches.

You need to quit yapping and start sharing! Ya been researching / engineering these things, prove it!

I played around a little earlier and started designing the rear pumpkin. This is a mock up piece, just working out dimensions. The final product will be much beefier.

[Lowgear]

It's always a good idea to over beef things as there's a lot of forces involved.

I know I know... I have to get working on my garden tractor class puller again. I had jwscab do all the machining on it late last summer. Then I worked on it a bit in the fall when it quickly got too cold to continue. Now that the warmer days are beginning again, I'll be picking it back up.

Here's a pic from last year of its hitch so you can see how high it sits above the rear axle. The entire puller ended up being complete garbage though which is why I'm building an entirely new one based off its design.

[morrisey0]

I still have no idea what I am doing, but I am doing it anyway! I keep having great ideas at about 5am of how I am going to work out something on this build, but when I sit down in front of it, the ideas aren't going to work. Oh well.

I have the basic design of the pumpkin worked out I think, if I keep it where it is. Right now, I have the d-shaft going through the chassis plates, but I may actually change it around and run the axle on top or bottom of the frame. Not sure on that one right now.

Next part is going to be drilling the HSS driveshaft for pins, at the spool and hopefully at the hex adapters. I have a couple of solid carbide drillbits, and am just hoping they will work. Then onto the drivetrain, which I still have no idea on. I have an old Graupner 1/8 nitro buggy that I stupidly converted to electric with CC electronics and Arrma drive parts, so I am going to rob them back soon and see if I can make something out of them. That drivetrain is what wakes me up at 5am.

Oh, and I named it! Since it is going to be a mostly printed rig with a steel backbone, I am going with Plastic Fantastic!