Frankenstein Build

[mjensen]

Originally Posted by Fricker08

Glad I could help man, I hope you figure something out!


Sent from my iPhone using Tapatalk

Thanks! Before I retired I worked for a custom yacht builder and we used a lot of carbon fiber and kevlar for various things. Unfortunately I was just a cabinet maker so I only really dealt with finished products like panels that needed to be incorporated into things like nav stations. I wish I'd paid more attention to the glass shop guys. I know the basics of doing layups and vacuum bagging, different resins and the like but I am clueless when it comes to the actual mechanical properties of carbon fiber like strength along the various axes (that really is the plural of axis), torsional rigidity, etc. Getting a cnc and playing with carbon fiber is something new for me and at my age learning new things doesn't seem to come as easy as it used to. Hopefully I'll figure it out before I get so old I can't get out and enjoy it.

[mjensen]

I made a little progress with the 6x6 today. Not with the rear frame section unfortunately but I think I've got the links from the skid to the middle axle figured out. The stock TRX6 uses upper and lower links that are close to the same length and with their mounting point keep the middle axle's pinions relatively flat through the suspension travel. Since I'm using much shorter links and my skid and frame rails mounting points are are not the same distance apart as theTRX6 it's been a chore to get the axle to remain flat during travel. On a 4x4 in wouldn't be a big deal but with the 6x6 you've got to consider the angles of the rear driveshaft running from the middle axle. Anyway, I think I've gotten the link lengths figured out and now I just need to redo the main chassis rail mounting points. One of the advantages of prototyping on a 3d printer...it's cheap to make changes and fix mistakes. If I was doing anything but the final product in carbon fiber, with all the mistakes and changes I've made I'd be broke.

[mjensen]

I made some progress this week. I've gotten all the link length sorted and the position of all the mounting holes in the rails located. Also,thanks to Fricker08, I think I've got the rear rail flex figured out. I stuck some temporary shock hoops on the rear to make sure there was no clearance issue with the suspension and it all looks fine. I just need to narrow up the braces where the rear axle links mount and I should be ready to cut some carbon (if I can ever get my head wrapped around the whole cnc thing). I just found out I have Lyme disease which the doctor explained may be why my head has been feeling so fuzzy for a while now. Kind of a relief since I was beginning to think I might be suffering from one of those old age brain related things that I'm not going to try to spell.


I don't no why that 3rd photo keeps posting in portrait mode or why it looks like I used a fish-eye lens. Everything actually turned out quite straight.

[Robotboy]

Looks good! Everything nice and low

[mjensen]

Originally Posted by Robotboy

Looks good! Everything nice and low

Thanks! If you wing it long enough eventually things "might" come together.

[twade984]

Glanced back through but didn’t see, do you know the wheelbase measurements by chance? Front axle to middle axle, front axle to rear axle?

Also, what was the reasoning behind the ar45 front? More offset on the diff to clear the vfd?

It’s coming together nicely, and look forward to updates!


Sent from my iPhone using Tapatalk

[mjensen]

Originally Posted by twade984

Glanced back through but didn’t see, do you know the wheelbase measurements by chance? Front axle to middle axle, front axle to rear axle?

Also, what was the reasoning behind the ar45 front? More offset on the diff to clear the vfd?

It’s coming together nicely, and look forward to updates!


Sent from my iPhone using Tapatalk

The measurement of the rear to middle axle is 130mm just like the stock TRX6. From the front to middle is 285mm. Overall WB is 415mm.

Honestly I picked the AR45p because it looked like it would be easier to convert to 4-link than the Traxxas axle. The offset difference on the pumpkin is maybe 5mm which did make getting clearance on the front driveshaft easier. Without the extra clearance I might have gotten a stock VFD to clear but the longer VFD I made for 550 can motors wouldn't have so I got lucky.

[twade984]

Okay that’s awesome, that’s a relatively stubby little guy for a 6x6. I can’t wait to hear how it drives. I’d like to have another 6x6 one day, so I’ll be keeping an eye on this. Thanks!


Sent from my iPhone using Tapatalk

[mjensen]

The Dravtech shocks showed up last week and I think the mediums may be overkill. I got them mounted with some temporary hoops but the rear of the truck sits a little high. I'm going to have to move the hoop mounting holes on the chassis rails a bit and make a hoops a little taller to get the truck to sit right. I also need heavier springs in the front. The whole chassis is still 3d printed so the changes won't be a big deal and once that's done I've got to bite the bullet and start cutting everything out of carbon.


My chassis seems to have about the same articulation as the stock TRX6. Traxxas claims the stock truck has 80mm of ground clearance but my stock one, without the weight of the body on it, only has 70mm. I've got about 65mm on my home made chassis but with the shorter distance between the front and middle axles I should still have better breakover angles.


In the picture of lifting the middle axle the front tire is slightly off the ground. In the others there was still a little travel left.

[mjensen]

One of the biggest headaches with both the VFD Capra build and this build has been finding a good place for the dig servo. Because the way the lever that activates the DIG that Vanquish makes for the VFD is oriented the servo is meant to be mounted behind the transmission. In both the Capra and the FJ45 body there isn't enough room to do that and keep the servo inside the cage/body. With some trial and error you could probably come up mount and servo horn combination that would allow the servo to be located forward beside the motor on the passenger side but there's not a lot on room inside the rails and outside the rails would need a pretty long servo horn that I'm not sure the micro servo would like. With the extra 10mm I add to the length of the VFD it's even worse so after a few tries I came up with a lever that pulls sideways rather than front to back so I can mount the servo beside the DIG. It's only 3d printed at the moment but if it works out I'll see about cutting one out a aluminum or carbon.

[mjensen]

And now for something completely different...well, maybe not completely different but somewhat different. I've made some progress figuring out the CNC but not enough to start ruining carbon fiber. So in the meantime I've decided to try something different. No long explanations...just a bunch of pictures.

[mjensen]

Well, I got a surprise tonight and not a good one. I hadn't had a driveshaft for the middle axle to the transmission until today (actually yesterday,since it's now 3:30AM) and was quite surprised to find the front wheels turn the opposite direction of the back wheels. Pretty stupid and expensive rookie mistake that I'm not sure I can fix. I decided on using the AR45p axle mainly because it looked like it would be easier to convert to SOA and 4 link than the stock TRX6 axle. Plus the pumpkin was slightly more offset so there would be less of a clearance issue with the front drive shaft. I should have known just looking at the axle that with the ring gear on the opposite side of the diff than the TRX6 it wasn't going to turn in the right direction but I completely spaced it. The pinion shaft on the Traxxas axle is about 5mm closer to the centerline of the axle housing than the Axial axle so there's no way the driveshaft will clear the motor in the VFD transmission. Not really sure what my options are at this point. Need to sleep on it I guess...

[twade984]

Well that’s a bummer man. I never noticed that myself


Sent from my iPhone using Tapatalk

[mjensen]

Originally Posted by twade984

Well that’s a bummer man. I never noticed that myself


Sent from my iPhone using Tapatalk

Yeah, pretty stupid on my part. Since the front of the chassis is basically the same layout as my VFD Capra and I used a Vanquish Capra front axle with an offset pumpkin on that, I had all the clearance and link issues pretty much sorted so I didn't spend much time with that end of the truck. I knew Joe over at Exocage was running a Capra front axle on his TRX6 mod so I never had a second thought about using an Axial axle. I'd forgotten that he had flipped the cover of the axle that holds the pinion over (from high pinion to low pinion) to make the axle turn in the right direction. I'm not sure if that's possible with the stock AR45p but it definitely can't be done with the Vitavon housing I'm using.



I need to look into what there is out there for other axles I might be able to make work.

[Fricker08]

Idk how much room you have behind the transmission, but some sort of reversing carrier at the back might be your best bet if you want to keep going with this thing.
That is a bummer I never would have guessed


Sent from my iPhone using Tapatalk

[mjensen]

Originally Posted by Fricker08

Idk how much room you have behind the transmission, but some sort of reversing carrier at the back might be your best bet if you want to keep going with this thing.
That is a bummer I never would have guessed


Sent from my iPhone using Tapatalk

I don't really have any room behind the transmission at all since I packed everything in there so tight to shorten the wheelbase. I suppose one solution would be to just switch to an AR45 straight axle for the front. Without the portals it should be turning in the right direction unless I've completely lost it. I don't know how much that would mess with the geometry or if I could adjust things enough to make it work without changes to the chassis.

If I can't find a fix I can always ditch the rear axles and put and put a AR45p with some longer links back there and have a 4x4. That's part of the reason I made the chassis 2 piece and split it where I did.

[350TacoZilla]

Remove the rear portals and flip the rear axles over then reinstall portals?

[mjensen]

Originally Posted by 350TacoZilla

Remove the rear portals and flip the rear axles over then reinstall portals?

Unfortunately because the axle housings are keyed to the portals and the way the link mounts are on the axle I don't see any way you could run them other than the way they are now. Thanks for the idea though!

[mjensen]

I think I had every offset pumpkin portal axle I own on the bench today checking measurements, link spacing, rotation direction, and how easy it would be to convert to SOA/4link. It's not going to happen with what I've got. I've looked online but other than Axial, Traxxas, and the folks that make aftermarket housings for those 2 brands there aren't a lot of people making offset pumpkin portal axles, at least not that I've found.


So I think it's time to stop uninventing the wheel. I think I've spent my RC budget for the next 3 or 4 months to get to this point and I seems pointless to spend anymore on it. All the Traxxas compatible parts can go on my TRX6 so they won't be wasted. And once my RC funds are a little better I can pick up an AR45p rear axle and convert this chassis into a 4x4 so it's not a complete loss. You win some, you lose some. As far as I'm concerned what matters is I had fun doing it.

[Fricker08]

Hey before you scrap the whole project, I know they’re expensive but I believe the vanquish scx10 iii axle housing would allow you to flip the ring gear. Therefore spinning it the correct direction. My buddy has the housings and I asked him, he sent me this pic. Good luck either way man! I enjoy watching your builds



Sent from my iPhone using Tapatalk