HPI Venture Overdrive transfer case project

[pwjm]

The final drive speed of the HPI Venture SBK is a bit spicy for my liking - furthermore it has no overdrive.

After speaking with Mike at Mike’s Tiny Truck Shop (youtube) - He was able to guide me on the gearing requirements.


It was determined that the Team Garage Hack Creeper-T Transmission (and Ali express clone) would be the appropriate final drive ratio, but also provide a 30% underdrive to the rear. The Stock T-case Ratio is about 1.5:1 and the creeper-T and Chinese knock off is 1.90:1 - So about a 28% reduction to the front axle and 77% reduction to the rear.

I set to work creating an adapter plate for the HPI Venture skid plate so I wouldn't have to drill any holes or modify the stock parts (I hate cutting OEM parts and making them weaker)

I've got to lube up the T-Case and loctite the screws, but the initial test fit looks good. The angle on the dog-bone shaft from the trans to the t-case is more than I'd like, but it shouldn't be a big deal to put a universal joint shaft in there if it looks like it's wearing too much.

The adapter plate can be found here: Printables

I'll update this when I get some more testing done on it: Things to do:

1. Add metal inserts for screws so they don't get ripped out if it gets warm, or stripped from going in and out too many times. (You can also use longer screws and nuts on top if needed - I have concerns about how much space is available for inserts)
2. Have the plate printed in SLS Nylon for strength

 

[HumboldtEF]

Nice work!
There were a bunch of Venture T-case parts on clearance for super cheap a few years back and I grabbed a bunch of gears with the idea of making an overdrive T-case. However I didn't do any math first like I should have, needless to say that didnt work out lol

I never really use threaded inserts and have good luck with threading directly into PETG or SLS nylon. I set the hole size at 2.6mm for M3 screws and its a tight fit, the screw will cut its own threads (wax/lube helps when its too tight or a long hole). I find this allows me to really tighten down screws without concern of stripping. The only way I run into trouble is if I run a screw in with power tools and overheat the screw and melt the material, hand tools are better/safer. But as long as you have enough thread engagement and dont overheat it its pretty solid.

That said I can see you dont have a ton of material. Instead of an insert you might consider throwing in a captive nut or whatever its called (model a hex hole for the nut to sit in on the top side of the print). That would allow the 3D print to be clamped between parts rather than threading directly into an insert which could pull loose in theory.

EDIT: the dogbone angle doesnt look bad at all, should be fine. Rear driveshaft looks a bit steep, though I can only see so much in a picture.

 

[pwjm]

Nice work!
There were a bunch of Venture T-case parts on clearance for super cheap a few years back and I grabbed a bunch of gears with the idea of making an overdrive T-case. However I didn't do any math first like I should have, needless to say that didnt work out lol

I never really use threaded inserts and have good luck with threading directly into PETG or SLS nylon. I set the hole size at 2.6mm for M3 screws and its a tight fit, the screw will cut its own threads (wax/lube helps when its too tight or a long hole). I find this allows me to really tighten down screws without concern of stripping. The only way I run into trouble is if I run a screw in with power tools and overheat the screw and melt the material, hand tools are better/safer. But as long as you have enough thread engagement and dont overheat it its pretty solid.

That said I can see you dont have a ton of material. Instead of an insert you might consider throwing in a captive nut or whatever its called (model a hex hole for the nut to sit in on the top side of the print). That would allow the 3D print to be clamped between parts rather than threading directly into an insert which could pull loose in theory.

EDIT: the dogbone angle doesnt look bad at all, should be fine. Rear driveshaft looks a bit steep, though I can only see so much in a picture.

Thanks for the tips! I'll see if I can incorporate the captive nuts!

I'll snag some more pictures tonight - I meant to grab a couple pics of the mounting plate for the ESC as well - I had to trim that slightly, but didn't feel guilty since it's not structural. I'm glad you think the dogbone looks okay - that's a relief. I'll try to get a better shot of the other axles.

 

[pwjm]

Nice work!
There were a bunch of Venture T-case parts on clearance for super cheap a few years back and I grabbed a bunch of gears with the idea of making an overdrive T-case. However I didn't do any math first like I should have, needless to say that didnt work out lol

I never really use threaded inserts and have good luck with threading directly into PETG or SLS nylon. I set the hole size at 2.6mm for M3 screws and its a tight fit, the screw will cut its own threads (wax/lube helps when its too tight or a long hole). I find this allows me to really tighten down screws without concern of stripping. The only way I run into trouble is if I run a screw in with power tools and overheat the screw and melt the material, hand tools are better/safer. But as long as you have enough thread engagement and dont overheat it its pretty solid.

That said I can see you dont have a ton of material. Instead of an insert you might consider throwing in a captive nut or whatever its called (model a hex hole for the nut to sit in on the top side of the print). That would allow the 3D print to be clamped between parts rather than threading directly into an insert which could pull loose in theory.

EDIT: the dogbone angle doesnt look bad at all, should be fine. Rear driveshaft looks a bit steep, though I can only see so much in a picture.

Here's a couple pictures of the drive line angles:

Close up of the trim I had to do on the ESC Tray.

Then Full Extension, Full Droop, and Bottom shot:

 

[HumboldtEF]

The driveshaft angles seem okay but you'll be a be a better judge than me. You can feel it out better by hand, check if the drive cup at the ends of the driveshafts are bottoming out and binding.

Side note I made a front crossmember that allows you to fit a smaller pinion if you want to gear down more: HPI Venture Low Gearing Motor/Servo Mount by HumboldtEF

 

[pwjm]

The driveshaft angles seem okay but you'll be a be a better judge than me. You can feel it out better by hand, check if the drive cup at the ends of the driveshafts are bottoming out and binding.

Side note I made a front crossmember that allows you to fit a smaller pinion if you want to gear down more: HPI Venture Low Gearing Motor/Servo Mount by HumboldtEF

Oh that's awesome! Nice work!

It's baffling that HPI didn't leave room to gear down pinion - especially when the overall final drive is so fast already. It's actually a really nice platform with some weird quirks.

At full extension there's still play left in the cups (they've got a surprising amount of range in them), and I'll be running it in almost full droop anyway.

I'll update this sometime down the road as time allows.

 

[Goro Majima]

This is pretty slick! As much as I think outside of the box, I have never thought of doing the Creeper-T in place of the transfer case. My rig is more of a trail truck but I do have a spare I can modify to a dedicated crawler with this mod. Btw the SBK kit at the moment only goes for $200 USD. Add this mod, run an outrunner setup and should be a fun straight axle capable rig.

 

[odomandr]

Cool mod to slow this down and give it some uphill advantage.