MAC FAB Bomber build, TAKE 2

[MAC FAB]

Yeti parts limit wheel travel by design. May give the Traxxas stuff a port and polish job.

[DavidH]

Originally Posted by MAC FAB

I've gototo make time to get back on this thing. Drove my first crawler today, a buddy got the TRX 4 Bronco. Much to my surprise, going slow was actually fun. So a question for the full indy or ifs crowd only. Is the steering angle adequate with your rig?

More than adequate.

I'm thinking I will want more than the +/- 45 degrees I get either way. Advice?

Design for zero Ackermann.

Consider solid axles.

[MasteroFlego]

The main thing restricting steering angle are the driveshafts, which is why 2wd drift cars have nearly 80°/80° steering angle. In 4wd, solid axles have the most steering angle, because the driveshafts only have to bend along one axis. To achieve more steering with a FIS rig, you'd have to go rear steer.

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[TheLetterJ]

I haven't seen it used in rc, but a double-cardan joint could be used at the wheel end to get more angle, given there is enough space to fit it. I know you're capable of pulling it off.

[MAC FAB]

I get 40/40 on the steering, with about -5 degrees Ackermann as it currently sits. So its not a drifter. I have another idea for tie rods, should get me closer to none by allowing me to move the bell cranks forward, ridding me of the Ackermann. Plan B is to run prop rods and mount the front shocks inboard. Guess this is why I'm not already driving it.........

[svt923]

Originally Posted by TheLetterJ

I haven't seen it used in rc, but a double-cardan joint could be used at the wheel end to get more angle, given there is enough space to fit it. I know you're capable of pulling it off.

A lot of onroad racing cars use double cardan shafts up front and I believe they have started using them in 1/10 scale 4wd buggies as well. Don't think any of the designs are strong enough to hold up in this application though, plenty of racers have blown them apart in tiny, little onroad cars.

[MAC FAB]

Originally Posted by svt923

A lot of onroad racing cars use double cardan shafts up front and I believe they have started using them in 1/10 scale 4wd buggies as well. Don't think any of the designs are strong enough to hold up in this application though, plenty of racers have blown them apart in tiny, little onroad cars.

I will look into these, potentially enabling more wheel travel at my given steering angles, but I'm not sure how or where you would calculate the pivot location for front arms. I've been trying to make rod ends this way, you got the invention wheels turning again.

[MAC FAB]

Can someone re-enlighten me with the front uprights/hubs that Hot Racing made to clear 2.2s? Time to get back at this thing.

[DavidH]

Dunno, but I believe losi modified the uprights for the rock rey (compared to the baja rey) for better clearance using 2.2s (the baja rey comes with 2.2/3.0).

[MasteroFlego]

Originally Posted by MAC FAB

Can someone re-enlighten me with the front uprights/hubs that Hot Racing made to clear 2.2s? Time to get back at this thing.

For slash 4x4? Those are made by Jconcepts.

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[MAC FAB]

Originally Posted by MasteroFlego

For slash 4x4? Those are made by Jconcepts.

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Thank you. More changes coming to this rig. Going to run Slash 4x diffs instead of the Summits, and will be looking seriously at 2 speed transmissions. Crawl mode and speed mode. Then I'll need a good motor/esc setup. My go fast car took the elctronics I had planned to run. Sucessfully grenaded to trans twice. Now I'm the only guy with welded gears/shafts in a Slash 2wd trans. Anyhow, redirection/remake in a good way, multipurpose rig in the redesign.

[MAC FAB]

How wide is your Bomber? As mine sits I am 13" od tire width mid stroke, with the SCORE TT wheel/tire combo. I am looking at getting my Bomber rtr wheel/tires on this thing, while increasing the width to 14" or even as much as 14-1/2" if that is what it takes. Front track changes about 1" overall as it cycles. In go fast mode it will be golden, but will it suck crawling with the wide stance?

[MasteroFlego]

Mine is about 11.25" wide, with stock hexes and #4 incision hubs.

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[MAC FAB]

I took my 2wd buggy out crawling today, down hill, not spooled, and all I can say is holy crap, mega travel indy suspension is incredible!!! No need to change the width or tires for that matter. Shot video for about 2 hrs crawling my local rocky hiking trail, hit the bottom and the motorcycle tracks, can you say send it? Its always fun until someone gets hurt, right? Lost an inner front wheel bearing so the tire went flying. 3+ hrs on the same battery. I am a happy camper today.

[MAC FAB]

20180519_173844 by MAC FAB, on Flickr
crawler 9_10666 by MAC FAB, on Flickr
20180519_174730_13769 by MAC FAB, on Flickr
20180519_180204_6563 by MAC FAB, on Flickr
crawler 4_4233 by MAC FAB, on Flickr

Screenshots from yesterday's go slow fun. Wrong forum for go fast footage. This was really great motivation for me to finish my build. Having 4wd would have been a blast, especially for front brakes.

[MAC FAB]

https://youtu.be/WvwACWgC9_w

[MasteroFlego]

Originally Posted by MAC FAB

Wrong forum for go fast footage.

Lol

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[MAC FAB]

That is only "kinda fast", about 30 mph. I need to go down about 5 teeth on the spur for "fast". Makes for a catch 22 on weight bias. Guess I'll shoot for 50/50. After watching this year's KOH, its only proper to be able to mob the rocks AND haul the mail.

[MasteroFlego]

Originally Posted by MAC FAB

That is only "kinda fast", about 30 mph. I need to go down about 5 teeth on the spur for "fast". Makes for a catch 22 on weight bias. Guess I'll shoot for 50/50. After watching this year's KOH, its only proper to be able to mob the rocks AND haul the mail.

30 is about how fast my pedes go, so in my eyes that is pretty fast.

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[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