MAC FAB Bomber build, TAKE 2

[MAC FAB]

Originally Posted by angrchair

Repashy's speed calculator spreadsheet says my Bomber does 33mph (underdrive) in the rear and 41mph in the front diff in second gear 1:1

My mind says 33 mph / 41 mph = a broken driveline after a wide open speed run through a good whoop section. That has to be stricktly a crawler setup and not U4, right??? I'm back to keeping the Summit diffs, I figured out a way to mount the stupid akward things and have them survive drivline torque twist. (They have the most useless mounting points and I can't use the goofy stock bulkheads) Lock 'em for the crawl and unlock for speed. If I were to start over, I would have built a chassis that the trimmed as required Bomber cage would mount to and be done building/rebuilding/rebuilding/rebuilding and actually be driving it. Wisdom applied in DMG's B2B program that I neglected to apply to mine. There is always room for a V2, right???

[angrchair]

Originally Posted by MAC FAB

My mind says 33 mph / 41 mph = a broken driveline after a wide open speed run through a good whoop section. That has to be stricktly a crawler setup and not U4, right??? I'm back to keeping the Summit diffs, I figured out a way to mount the stupid akward things and have them survive drivline torque twist. (They have the most useless mounting points and I can't use the goofy stock bulkheads) Lock 'em for the crawl and unlock for speed. If I were to start over, I would have built a chassis that the trimmed as required Bomber cage would mount to and be done building/rebuilding/rebuilding/rebuilding and actually be driving it. Wisdom applied in DMG's B2B program that I neglected to apply to mine. There is always room for a V2, right???

the speed difference shouldn't hurt anything since there is such loose traction, in a 1:1 vehicle at highway speeds yeah there would be issues. Especially tire wear, but as for offroad rc, I doubt there will be anything noticeable.

Under-driving the rear helps uphill/crawling because it keeps the vehicle from wanting to wheelie so much and flip over backwards. They make the under-drive set for this reason.

[MAC FAB]

20180601_203333 by MAC FAB, on Flickr

20180601_203357 by MAC FAB, on Flickr

20180601_203219 by MAC FAB, on Flickr

20180601_203521 by MAC FAB, on Flickr

5 steps forward, 2 steps back as usual. If all goes well tomorrow, the rear diff will get mounted. I was planning on mounting it to the 1/8" hr steel chassis skid plate that got built tonight, not so. Pinion has to point up about 20 degrees to miss all the suspension stuff going on out back, so now it has to hang from the 18 ga cr steel box I built that took the place of the "fuel cell". That box and it fasteners will tie into the shock mounts and to the chassis pan as well to get some more structural integrity. Notice the back skid plate. Another 18 ga cr piece. Helping to get the rig back to a 50/50 weight bias.

So here is the question: Keep it because it will slide over stuff or remove it because it will hang up on stuff? What says the peanut gallery?

[MAC FAB]

20180130_182449 by MAC FAB, on Flickr

20180602_173206 by MAC FAB, on Flickr

Ever wonder why you always see vise grips on my build? Things are always changing!!!
New front shock mount today. Top pic is the old, OEM location on top, bottom pic is the new. Stiffer front end now which was needed. Yeti shocks may work now. The steering bell cranks can move forward to where they should be, which is another good thing. No shocks to interfere with the tie rods, only the axles, which the gremlin I had with them is now figured out. It now will also be easier to tie the nose to the chassis pan with the new shock mount as well. 5 steps forward and none back today.

It wishes it ran!!!!!

20180602_172911 by MAC FAB, on Flickr

[MasteroFlego]

I don't own any vice grips lol

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[MAC FAB]

Originally Posted by MasteroFlego

I don't own any vice grips lol

Sent from my Nexus 5 using Tapatalk

Notice that 1 vise grip is missing!!!!!!!

Temporary shock mount instead. I have some shocks that are long enough to be bypasses, maybe.......
Little update: New shocks up front off some AE monster truck, same length shock body as the Slash rears, but with an additional 1/4" of stroke. Rear diff is 80% mounted so I can see whats happening with the axles. Somehow that mess needs to get tied into the chassis as a structural element. What you see here (axles) is for mock up, not the parts that will actually be run, those are the driveline pieces going through the chassis to the trans/motor. Shooting for this to be a roller by next weekend, fingers crossed.




20180706_084918 by MAC FAB, on Flickr
20180706_084757 by MAC FAB, on Flickr
20180706_084741 by MAC FAB, on Flickr

[MasteroFlego]

Originally Posted by MAC FAB

Notice that 1 vise grip is missing!!!!!!!

Temporary shock mount instead. I have some shocks that are long enough to be bypasses, maybe.......
Little update: New shocks up front off some AE monster truck, same length shock body as the Slash rears, but with an additional 1/4" of stroke. Rear diff is 80% mounted so I can see whats happening with the axles. Somehow that mess needs to get tied into the chassis as a structural element. What you see here (axles) is for mock up, not the parts that will actually be run, those are the driveline pieces going through the chassis to the trans/motor. Shooting for this to be a roller by next weekend, fingers crossed.




20180706_084918 by MAC FAB, on Flickr
20180706_084757 by MAC FAB, on Flickr
20180706_084741 by MAC FAB, on Flickr

Don't know what it is about that rear setup, but it's very appealing to me.

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[MAC FAB]

Originally Posted by MasteroFlego

Don't know what it is about that rear setup, but it's very appealing to me.

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Wish I could say the same about the front. Got the front driveline in, front wheels turning happily. I get 45 degrees either way in steering, but the stinking bell ranks hit the center shaft at full lock. Soooooo annoying. I like the larger shafts because of the 6mm input/outputs on the diffs, no replacing worn parts because they're huge. Slash 4x up front....???

[MasteroFlego]

Originally Posted by MAC FAB

Wish I could say the same about the front. Got the front driveline in, front wheels turning happily. I get 45 degrees either way in steering, but the stinking bell ranks hit the center shaft at full lock. Soooooo annoying. I like the larger shafts because of the 6mm input/outputs on the diffs, no replacing worn parts because they're huge. Slash 4x up front....???

Pics? I think I know what you mean but I'm not sure. What Bellcranks are you using?

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[MAC FAB]

Modified Slash 2wd bell cranks, simply because I have some lying around. I think I now have it working, I just need to raise the bell cranks about 1/8" more, then I will lose the bump steer I now have at full droop and also clear the front drive shaft. Steering servo should tuck nicely into the drivers side of the cage, leaving plenty of room for everything else. Probably going to spool my extra 2wd Slash tranny so I can be test driving it before too long. I'll post a couple pics tomorrow so you can see. Then I need to figure out how I'm going to align the thing. Guess I should square the chassis up then align the cage afterwards. Ideas anyone?

[MAC FAB]

20180724_195513 by MAC FAB, on Flickr

20180724_195648 by MAC FAB, on Flickr

[MasteroFlego]

That driveshaft doesn't look centered :p, and to increase clearance maybe instead of using plastic driveshafts you could find some smaller sized steel dog bones? technically those Bellcranks are upside down, though they probably wouldn't work properly right side up. You should also make a top plate to stop the screws from bending

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[MAC FAB]

Originally Posted by MasteroFlego

That driveshaft doesn't look centered :p, and to increase clearance maybe instead of using plastic driveshafts you could find some smaller sized steel dog bones? technically those Bellcranks are upside down, though they probably wouldn't work properly right side up. You should also make a top plate to stop the screws from bending

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Good eye and correct. Bell cranks will be double shear with a gusset leg to somewhere, I'm still working the geometry. Driveshaft is offset, have no choice there. All the metal axles available are huge on the flange, whopping 6mm output shaft. I could make dog bones I suppose, hadn't thought about that. With the bell crank upside down AND backwards, it eliminated the Ackermann altogether. Sadly, I can't run it that way and have it work. I have another idea for the spreader where the rod ends at the bell cranks are vertical instead of flat. Tie rods connect where they may, speaking of elevation, (upside down bell cranks with a lift kit) I really don't want bump steer. Just another day in the scratch build life.........

[MAC FAB]

What is the secret to "un-glue" my RTR Bomber tires from their rims and not destroy the foams in the process? Those would look great with my RC4WD M/T aluminum beadlocks. This all comes about because of front suspension rethink 3.0. As it sits, I can bury the chassis by a good 1/2" with the SCORE tires, 2.2s may bottom with the chassis, its close. So to dismount them, what is involved? Thanks in advance for solutions!

[MasteroFlego]

Originally Posted by MAC FAB

What is the secret to "un-glue" my RTR Bomber tires from their rims and not destroy the foams in the process? Those would look great with my RC4WD M/T aluminum beadlocks. This all comes about because of front suspension rethink 3.0. As it sits, I can bury the chassis by a good 1/2" with the SCORE tires, 2.2s may bottom with the chassis, its close. So to dismount them, what is involved? Thanks in advance for solutions!

Option 1, acetone. This may destroy your foams, but they suck anyway. Dangerous chemicals, dangerous fumes, smelly.

Option 2, boil. This may destroy your foams. Smelly, potentially toxic fumes.

Option 3, baking. This may destroy your foams. Smelly, potentially toxic fumes.

Option 4, freezing and breaking the glue. This is the only one I've done, I wouldn't recommend it. It's a huge PITA and you almost certainly will damage the tires in the process.

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[MAC FAB]

I'll try acetone. Got one bead broken free by hand; now I don't leave thumbprints, they're worn off. Came close to getting a set of UDR takeoffs, but I have no desire to deal with the hubs. Could alway use them on my Summit project......

[MAC FAB]

How about this????? Easily stretched onto the wheels with Axial foams. Yes MasteroFlego, I now see that they do suck!!! !/4" deep of acetone in a round crock the size of the tires and I was golden. Came off like butter, one side at a time.


20180810_095422 by MAC FAB, on Flickr

20180810_095449 by MAC FAB, on Flickr

[MasteroFlego]

Looks good, how did you get the rear bead in?

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[MAC FAB]

Simply pushed it onto the rim, fought the inner piece a bit, clamped the outer ring and added the 10k screws. These are the only beadlocks I've used, so I have nothing to compare them to. Funny thing was the outer bead on the RTRs came off pretty effortlessly, the inside was another story.

[MAC FAB]

20180811_140026 by MAC FAB, on Flickr

20180811_140043 by MAC FAB, on Flickr

20180811_140105 by MAC FAB, on Flickr

It is quite different looking with the gigantor tires on it, don't ya think? I'm really liking those M/T wheels as well, especially since nobody has them. So now the question wil be to run a spare or not. I'm leaning slightly towards not. Either way, I'll be building a beauty queen that is also a tom boy, not afraid to get dirty. I can't wait to get the body going on this thing. Those who go to Glamis and are familiar with the big bodied sand/pre runner cars, you're going to see something very similar here. No flat body panels like you see on it now, instead it will be screaming with shape.

As it sits, she weighs an even 8 lbs . Looking to be a every bit of 10 lbs when done, so what motor speedy combo will give me 20 mph on top and crawl like a sloth, and still run cool at 10+ lbs? How about drag brake that will actually hold the toad at a standstill on a slope? Right now there is room for literally anything. 2.83 ratios in the diffs for what its worth. 3s power is fine, using the airplane soft packs that I have in the factory battery box.