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Old 08-31-2017, 02:40 PM   #21
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Nice project, good job man !

It's like an Exo but without the 10 000 screws to change a lipo
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Old 08-31-2017, 06:30 PM   #22
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

That's an unusual name for the dog breed! I've never seen even a single 'Australian Shepherd' dog in Australia! lol Looks a lot like a Coolie.

David, have you had a chance to run the sensored system yet to see how it crawls compared to the old unsensored system?
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Old 08-31-2017, 10:37 PM   #23
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Quote:
Originally Posted by Brake Weight View Post
I've been buying the stainless rod that threads down to an m5 thread. It's a little big for the Revo ends but the RPM ends handle them well. Especially if you tap the RPM ends to an m5, too.

But you'll need a 5mm rod to make m4 threads. 6mm will make m5. The rod I've been using is an SAE measurement that's 1000ths bigger than 6mm.
I tried earlier to cut a M4 thread onto a 3/16 (.186") rod, and it did not go well. I may have ruined the die as it would not begin the cut a thread into this new stuff (.155").

So I used the 10NC24 die and and it cut some threads that worked (but tight) into a Traxxas 5525 rod end. I tapped matching threads into the endlink, and I think its a usable solution.

I'll get a replacement M4 die and try that later. It's not for this project anyway.
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Old 08-31-2017, 10:45 PM   #24
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

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Originally Posted by CoolRunning View Post
That's an unusual name for the dog breed! I've never seen even a single 'Australian Shepherd' dog in Australia! lol Looks a lot like a Coolie.
My wife informs me that the breed is now being called the "American Shepard". :shrug:

The Australian Shepherd is from: A) Australia, B) England, C) Spain, D) None of the Above

Quote:
David, have you had a chance to run the sensored system yet to see how it crawls compared to the old unsensored system?
Not yet. I ran it across the garage floor to test the aux wire and shift linkage, it was very smooth, and then the front dogbone fell out, reminding me of the broken toe block.
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Old 08-31-2017, 11:22 PM   #25
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Quote:
Originally Posted by DavidH View Post
I tried earlier to cut a M4 thread onto a 3/16 (.186") rod, and it did not go well. I may have ruined the die as it would not begin the cut a thread into this new stuff (.155").



So I used the 10NC24 die and and it cut some threads that worked (but tight) into a Traxxas 5525 rod end. I tapped matching threads into the endlink, and I think its a usable solution.



I'll get a replacement M4 die and try that later. It's not for this project anyway.


I tried an m4, too and it wouldn't thread. I had a set so I cut the galled end and tries the m5 and it works. But the Traxxas ends don't have enough meat on them and I broke one. So I ordered some of be beefier RPM ends. Same measurements as Traxxas, but more plastic and the RPM proprietary special magical plastic.
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Old 09-08-2017, 12:02 AM   #26
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Quote:
Originally Posted by CoolRunning View Post
David, have you had a chance to run the sensored system yet to see how it crawls compared to the old unsensored system?
As I haven't yet sorted the 2.2 foams, I bolted on the MX28 Badlands, and dug up the front garden for a bit.

There is a rock there with a steep face which would easily - at dead slow - stall out the unsensored rtr motor in high gear; in low gear, sensored or unsensored, this rock was easy to walk over. The difference was that I could now do it in both low and high gear.

(My yeti prior to the IRS conversion, and that rock)


Took it out onto our big back lawn, and promptly blew out the rtr front gears after a few minutes of bashing.

Swapped in new HD gears that night, put in 500K cst diff fluid, and on Monday I took it out and ran a pack through it in the trails, on the rocks, and some speed runs, without any major incident. The power and speed were as expected (lots!).



What is not apparent in the video is how controlled you have to squeeze the trigger on the way to full throttle, so as not to loose traction on this very loose and dusty surface and spin out. It's clear to me why 4wd buggies like the slash run open diffs f/c/r, to provide stability in this situation that the yeti won't have with its locked rear and lack of centre diff.

Unfortunately, I neglected to bring my infrared thermometer, and while things got toasty, it never thermalled, but then I didn't try to make it overheat. The fan on the esc kicked in promptly, and I using a castle fan on the motor.

Sensored vs the 2-speed...

In low gear, the sensored operation took the rough edges off of the low speed crawling/climbing.

In high gear, it allowed for smooth startup speeds, but didn't drop the throttle response to how it is in low gear. More importantly, I understand that it isn't a substitute for appropriate gearing; the lack of efficiency and strain on the motor and ESC is still there even if the slow speed operation is smooth, and for those same reasons full size EVs - Teslas, for one - would be already using multi-gear transmissions, if they were able to handle the torque of the current motors.

I can see how one may be able to make (or have to make do) due without the 2-speed, by dropping the overall gearing down, and/or taking advantage of the larger (compared to the rtr equipment) ESCs' higher heat capacity which may be enough for part-time crawling. It very much depends on your overall gearing, vehicle weight, and how you intend to use it.

Since the option is available to me, and that I typically spend most of my time in low gear on the trails, and having had a chance to run this sensored system with the 2-speed, I'll say that I like how the character of the truck changes with the different ratios, with the knowledge that the motor is geared appropriately for the task at hand. The 2-speed makes the truck more versatile; sensored just makes it better.

Speaking of better, the ESC's aux wire function far outshines the sensored operation of this combo for me. Being able to switch between the rock-racer and crawler modes (reverse and drag brake toggles) is just the thing to add to this vehicle's versatility. While it was not an issue for me, I hope they add the reverse travel option to the firmware, to make it more accessible for others, and eliminate the (possible) need for an external servo reverser when it shares the rx channel with the shift servo.
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Old 09-08-2017, 06:47 PM   #27
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Cheers David for a very in depth review!

I had a hunch sensored might be more like this after seeing a sensored rig crawl slowly. I hazarded contrary to what is usually said that to crawl with precision requires appropriate gearing no matter the motor type or if it's sensored or non sensored setup though naturally sensored would be clearly smoother than non sensored.

The funny thing with my RR was locking it up. I ended up with a more stable truck though saying that I run solely on loose stuff. Maybe foams were a biggie but when it had a centre diff it constantly unloaded to the front and became a one wheel drive truck which often made it pirouette at speed when you were on the gas. Centre lock helped that big time. I always found the Yeti super stable and more predictable with the locked diff which is why I wanted to try the RR locked.

I think I'll have to try the 2 speed in the Yeti even with the stock motor as I love it in the Bomber.

One question about temps.

I'm running a cheap HW 120 SC8 ESC and after a major 3S thrashfest in say 30C weather it would get to say 48C which was very impressive. How hot did the Castle get do you think?

I've read talk of them getting a tad warm and a MMP I saw run was constantly running the fan (it would turn off after a while) which I believe indicates 140F which is fairly warm when our trucks were probably 25C max in the exact same conditions.

I really want to try sensored for the RR as I have no 2 speed option but am not sure if I'll spend good money and disappointed with either the slow speed performance (I don't think I can really gear down and volt up with the Losi) or have some heat issues in Melbourne summer. I can get a HW sensored system which believe has plenty of headroom at 140A but it's not waterproof.

First world problems for sure!
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Old 09-09-2017, 10:19 AM   #28
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Quote:
Originally Posted by CoolRunning View Post
Cheers David for a very in depth review!

I had a hunch sensored might be more like this after seeing a sensored rig crawl slowly. I hazarded contrary to what is usually said that to crawl with precision requires appropriate gearing no matter the motor type or if it's sensored or non sensored setup though naturally sensored would be clearly smoother than non sensored.
And not just throttle response, but heat and stress on the motor and electronics. When Tesla had to give up the 2-speed transmission, they had to compensate with modifications to the motor and electronics to handle the extra heat generated by the single-speed arrangement. It's just not as readily apparent with these small scale vehicles.
Quote:
The funny thing with my RR was locking it up. I ended up with a more stable truck though saying that I run solely on loose stuff. Maybe foams were a biggie but when it had a centre diff it constantly unloaded to the front and became a one wheel drive truck which often made it pirouette at speed when you were on the gas. Centre lock helped that big time. I always found the Yeti super stable and more predictable with the locked diff which is why I wanted to try the RR locked.
I've had several 1:1 4WD trucks, and I'm on my second AWD car, and I've pushed them all hard on a variety of surfaces, and done my share of suspension tuning.

Let me take apart my 'stability' comment into two pieces, for how I was applying it to my yeti in that video.

- Stability on acceleration; an open rear diff will be more stable on loose surfaces, at the cost of reduced traction. With silly putty, the rear diff was functionally locked.

- Stability on deceleration/turning; a locked front diff will cause the outer front tire to tuck under and flip the truck. The switch to 500K cst worked well for that high speed section in the video. Not so good for crawling. I'm gonna put the putty back in.

I haven't examined the rock rey in motion, but it seems (to me) an odd combination of locked rear and open centre and front, when for traction and stability on acceleration you want that centre diff locked. On my AWD Mazda GTX "homologation special" the centre locker was standard, the rear locker optional/3rd party.

I presume that Losi chose this arrangement for the tighter turning radius, more stability on decel/cornering, and hoped that the AVC would electronically (attempt) to counter the effects of the locked rear diff.

The thing about locking the centre diff is that (based on my experience with 1:1 trucks/suvs) it messes with the both traction control and ABS, and I suspect that in the losi that it works against the AVC, if you have not already disabled it, and that the version of AVC in the RRey includes throttle management.

Torque twist and weight transfer also factor in to what you are observing, in that it is what is lifting the one front tire up on acceleration and loading up the rear tires. With an open centre diff, torque will be sent to the axle with the least traction (front), and then when the now-spinning-faster fronts (or in this case, one of the fronts) finds traction, it produces the pull/spin that you observed. Your locking of the centre diff would have addressed this issue.

The spektrum rx currently in my yeti has AVC, and I struggle with my CDO (Compulsive Disorder of Obsessiveness) to leave it alone. I have purchased the electronics that would allow me to toggle channels 3&4 between "shift & rear steer" to "AVC gain and sensitivity" , but I didn't leave room for it in this current layout. Maybe.

Quote:
I think I'll have to try the 2 speed in the Yeti even with the stock motor as I love it in the Bomber.

Quote:
One question about temps.
This prompted me to pull the logs () out of the esc; I'll post that in a separate post.
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First world problems for sure!
lol.
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Old 09-09-2017, 11:51 AM   #29
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Quote:
Originally Posted by CoolRunning View Post
...
One question about temps.

I'm running a cheap HW 120 SC8 ESC and after a major 3S thrashfest in say 30C weather it would get to say 48C which was very impressive. How hot did the Castle get do you think?

I've read talk of them getting a tad warm and a MMP I saw run was constantly running the fan (it would turn off after a while) which I believe indicates 140F which is fairly warm when our trucks were probably 25C max in the exact same conditions.
It wasn't til you asked that I recalled that the data logging was enabled in the esc.

Air temperature was 25 C that day.

I cropped this out of the graphed output showing the esc and motor temps and power output.



Numbers:
- Current, Max: 58.7A
- Watts, Max: 860W
- ESC Temp, Max, 57.4C
- RPM, Max: 114687
- AUX mode, average: 62% (not really indicative, in this still-testing phase)
- Motor Temp, Max: 34.5C

PM me and I'll send you the .cst file if you want, so you can load it into the castle software yourself and poke at it further. This geek is impressed with what castle has provided here.
Quote:

I really want to try sensored for the RR as I have no 2 speed option but am not sure if I'll spend good money and disappointed with either the slow speed performance (I don't think I can really gear down and volt up with the Losi) or have some heat issues in Melbourne summer. I can get a HW sensored system which believe has plenty of headroom at 140A but it's not waterproof.
I picked up a knock-off Hobbywing Xerun 120A SD v2.1 Sensored Brushless ESC for $20, with plans to use it in my next project (with a sensored castle motor), but now that I see what the mamba x can do I may reconsider.

The way to reduce the heat is to drop the kv and go to 4s (and a 4s-compatible motor) to get the speed back. And, to break more stuff, with 1/8th scale power levels . I don't want to buy 4s battteries, break more stuff, and I don't need more speed. At this time .

Assuming you want to stay with your 2/3s batteries: The RRey has a 6-pole motor in it, so I don't know what would be the equivalent for kv/rpm/torque in an alternative sensored motor. I'm guessing you'll be staying in the 2800kv area. Others more knowledgable can chime in here.

To handle the heat in the absence of the lower gearing would be provided by the 2-speed, put a fan on the motor and get the bigger mamba monster X, locate the esc so that it has lots of fresh air available to the fan intake, and track the temps via the data logging feature. I'm curious to see if one could adapt the big heat sinks that I use for the computers I build for the ESCs in these cars. It would be a matter of removing the existing heat sink, and/or connecting it in manner that would be sufficiently thermally efficient to make it worth while.



I'm guessing that if you are not crawling a lot with it, or purposefully trying to stall the motor while climbing, the heat management built into the MMX may be sufficient all by itself. And if it does overheat, dropping a few teeth on the pinion may be sufficient to fix it.

Last edited by DavidH; 09-09-2017 at 02:42 PM. Reason: titpo
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Old 09-11-2017, 10:51 PM   #30
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Arrgh.

To maintain the caster in the suspension rear geometry (so that the caster for the rear wheels is in the same direction as the front), I have to run the c-hubs forwards to the truck, but backwards to the knuckles.

In my initial testing this did not appear to be a problem, I simply added some negative camber and all was well...

As I pushed it harder, particularly with the new power system, it appeared that the rear dogbones were slipping within the drive cups (during braking, at full droop), and the left rear dogbone came out several times (crawling/climbing, at full droop). The fronts have not been a problem.

For the next time out at the crawling spot I installed one of the RTR dogbones on that side, to alleviate the symptoms. However, I could not leave it like that.

I am attributing the problem to some combination of the backwards chubs, shorter 92mm axles, maxed-out droop (limited by the knuckles being able to swing over the LCAs), and manufacturing tolerances (the problem is not symmetrical/equal to both sides). Possible fixes:

- travel limiters, such as straps or fuel tubing internal to the shock.

- slash rear arms; they are a bit shorter, and would pull the dogbones into the cups, but they are not very compatible with rear-steering knuckle arms at droop.

- longer aftermarket axles; more $$ and they are not without their own problems.

I got creative, and effectively shortened the LCA by drilling a new hole just inboard of the factory hole, filling the old hole with a cut-up section of LCA hinge pin. This moved the dogbone 3mm into the drive cup, which still allows for full compression without bottoming the out the drive shaft in the drive cup.

While this worked perfectly for the left side, and has tested out great, I have realized after the fact that if I grind a flat spot on the 'filler' hinge pin section I can fine tune how much the procedure shortens the LCA (1-3mm) the next time. The LCA does need a bit of reshaping to allow the c-hub to move without interference in the upper range of movement.

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Old 09-14-2017, 02:20 AM   #31
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

I really enjoy following your tinkering and am quite impressed by your workmanship, but your build begs the nigh on philosophical question of when a Yeti is no longer a Yeti, but something else instead. 4-wheel steering and IRS - still a Yeti? Or has it become a different kind of animal?
A Meh-Teh perhaps? Maybe snow leopard - rare, fast and dexterous?

But whatever the beast, I am grateful for your detailed posts. Keep it up!

Last edited by Antsiranean; 09-14-2017 at 02:23 AM.
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Old 09-14-2017, 01:12 PM   #32
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

This is the left rear dogbone end of the 92mm universal; sits nicely in the drive cup, virtually the same as the other side, at max droop, following the mod to the LCA.

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Old 09-14-2017, 01:26 PM   #33
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

New stuff. These are the firmest springs from axial for the factory shocks; this should maintain more ground clearance with less preload, but may not allow for articulation I want. Time to experiment. I expect they'll need a corresponding change to the shock oil.

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Old 09-16-2017, 01:28 PM   #34
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

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Originally Posted by Antsiranean View Post
I really enjoy following your tinkering and am quite impressed by your workmanship, but your build begs the nigh on philosophical question of when a Yeti is no longer a Yeti, but something else instead. 4-wheel steering and IRS - still a Yeti? Or has it become a different kind of animal?
A Meh-Teh perhaps? Maybe snow leopard - rare, fast and dexterous?

But whatever the beast, I am grateful for your detailed posts. Keep it up!
Thanks!

You've raised a good question. It is my understanding that in these forums that vehicles are typically classed by their axles and basic suspension design. If you were to take an SCX10 and swap out the axles for wraith AR60 axles, you no longer have an SCX10. Likewise, if you look at my Clod Buster, with its hand-made low-CoG chassis, three steering servos, and '69 Camaro RS/SS body, it is still very much a Clod with its factory motor-on-axle setup.

OTOH, the Axial Bomber is based on a real vehicle; even if you swap out the suspension, keeping the Bomber cage and look makes it a Bomber.

The Yeti is an odd duck, as it is not based on a real vehicle, but since my yeti is still all yeti, I'll call it a yeti for now. Although 'snow leopard' does get some traction with me. Perhaps a new colour scheme, and see how it goes this winter with the 2.8 Badlands tires on it.

My next project in the works will use an RR10 skid and some AR60 axles, with most of the interconnecting bits fabricated by me. No cage, just a truck body. Is that enough to call it a Bomber? No, but it should still be an RR10, a 10th scale rock racer with the same front and rear suspension geometry, but without the bomber cage.
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Old 09-16-2017, 01:29 PM   #35
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Some ebay goodness. Now to wait for the new wheels.

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Old 10-08-2017, 04:52 PM   #36
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

I think it was Screamer that suggested these in another thread, so I picked some up to try them out.



$20 of traxxas parts yields 2 yeti driveshafts. The yokes need to be drilled out to 5mm, and shaved slightly to slide far enough on to get the pin in, and the transfer case needed a tiny bit of clearancing so everything could spin freely.

The metal u-joint was a bit tricky to assemble without the traxxas tool, but it went together without injury to myself or the parts.



I may not use these right away, but for the price I wanted to have them handy for this or another project.
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Old 10-18-2017, 12:45 PM   #37
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Ebay wheels finally arrrived. Impressive fit and finish for US$56 for four.



Cleaned the tires around the beadlock area, and wrapped them around the CI foams.



Locktite on everything, and they went together without issue.



Unfortunately, the annual Vancouver Rain Festival is well under way, so I'll have to wait to test these out.
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Old 12-06-2017, 04:56 PM   #38
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Default Re: Not according to the instructions... (IRS/4WS Conversion)

Such a sweet build. I follow UCFab on Instagram and his FIS cars look unstoppable on the rocks!

Any chance you can post up the seller of those wheels. Ignore the haters!
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Old 12-06-2017, 05:40 PM   #39
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Originally Posted by nedmo View Post
Such a sweet build. I follow UCFab on Instagram and his FIS cars look unstoppable on the rocks!

Any chance you can post up the seller of those wheels. Ignore the haters!
You have a pm.
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