Restoring my old Big Bear

[Macinnis 226]

30 minutes ago, mongoose1983 said:

I have yet to see a sticker staying over a 3D printed piece. Did you sand and polish those lamps?

By the way, what is your opinion on the MCI stuff? Good or not?

And of course, Ohhh that BIG BEAR looks juicy. As Peter Criss would say THAT'S THE KIND OF SUGAR PAPA LIKES!!

 

 

You are correct, stickers don't stick to 3d printed material worth a darn.  The MCI Racing stickers are good.  They included several extra stickers just in case.   It came with 4 of the KC stickers so I wasn't worried about messing up those 2.  It also had several stickers that were not included in the original sheet but fit the truck well if you wanted to use them.  Shock, battery, smiley KC stickers, extra Big Bear lettering in black and an extra over sized bear.  It took a couple hours to cut them all out but they went on very easily and fit the contour of the trim perfect.  I would use them again.  The original stickers are on ebay now for $59.99 US and these were $15 shipped.

 

Shapeway on the other hand, replied that they are investigating me getting the wrong part but I have not heard anything since.

[mongoose1983 3335]

1 hour ago, Macinnis said:

You are correct, stickers don't stick to 3d printed material worth a darn.  The MCI Racing stickers are good.  They included several extra stickers just in case.   It came with 4 of the KC stickers so I wasn't worried about messing up those 2.  It also had several stickers that were not included in the original sheet but fit the truck well if you wanted to use them.  Shock, battery, smiley KC stickers, extra Big Bear lettering in black and an extra over sized bear.  It took a couple hours to cut them all out but they went on very easily and fit the contour of the trim perfect.  I would use them again.  The original stickers are on ebay now for $59.99 US and these were $15 shipped.

Thanks a lot for the review, pal! I'll checking the online MCI catalog. And again, thanks for sharing this here in the Forums. ALWAYS a pleasure to see a Big Bear truck! Do you know these were the very first monster trucks to be released in RC fashion. I hope I can come across a nice Big Bear resto project not long from now

 

[Macinnis 226]

I knew the Big Bear was an early model. Did not realize it was the first monster truck.   I think mine was originally a version 2 so it seems like it was 1989-1990. I just remember thinking when I get older and have my own money I'm going to own every model.  That was my main motivation for restoring this one.  I am sure I have more in the resto than was paid for it back then.  It was 2 weeks of entertainment so it was worth it.

On a side note, Shapeways started production on the new body mount i didn't get my first order and are sending it free of charge.  This is my first order from them so I'll give them a thumbs up once the new part comes in.

[Macinnis 226]

Quadruple post! sorry

[Macinnis 226]

Quadruple post!

[Macinnis 226]

Quadruple post

[Macinnis 226]

The last problem with my Big Bear was the idler gear shaft wobbling.  I "hope" this was the popping noise I heard last time I had it assembled.  The shaft had a lot of play side to side so I looked at every hardware store in miles trying to find a sleeve or eyelet or new slightly larger shaft that would correct the issue.  I stumbled across this MIP Idler shaft case save part #BB-C on ebay.  It's not so much a sleeve but a cap that completely covers the plastic hole the shaft inserts into.  So now it has the metal heat sink plate on the motor side and the new metal case saver cap on the plastic gear side and it seems solid.  Took it for a test run on the hardwood in the living room and it spun perfect donuts with no popping.  Once I get a new ESC for my Bush Devil 2 I will use the Tamiya ESC in the Big Bear.  Right now the Big Bear manual controller acts like it has 200% reverse speed and it feels like its too much on the gears.  The Tamiya ESC is factory set for first click reverse is brake, second click is 50% reverse.  I think that will be better on the gears.

[waterbok 1282]

Clean and regrease every race day, lol, such an easy gearbox to take apart. Nice picture on that hopups might make that reinforcement on my lathe.

[Macinnis 226]

If got the chance to take the big bear out in the sunshine today and was running it around the yard and it was doing great till a few minutes in it started making a weird grinding noise and would barely move. Fearing the worst I stopped immediately and the motor was hot and smelled funny.  I assumed I stripped one of my new gears.  I opened the gear box up and everything looks fine. Loosely putting the gearbox back together the differential works smoothly and quietly.  As soon as I hold one tire and spin the other the grinding noise starts.  Do silver can 540s wear out?  Any thoughts why it's overheating so fast and smells so terrible?  I'm using a 7.2 nimh 2000 mah fresh battery and everything else is stock including the manual speed controller. 

[waterbok 1282]

What happen if you turn both wheels in the same direction this should rotate the motor without activating the inner gear diff.

[Macinnis 226]

Same thing. Clicking noise. I almost know it's the motor but I can't imagine a motor making this sound.  If it was gears they would have been shredded and they are all fine. 

[Macinnis 226]

i opened the gear box and used half the rear end to watch and ran the motor with a AA 1.5v battery.  After about 30 seconds the motor started smelling terrible.  The gears seemed to be syncing up fine.  Is it worth pulling the 25 yo 540 silvercan apart and cleaning it?

 

Edit: I pulled the gearbox apart one last time and I guess the noise is the idler gear stripping the differential gear.  It looks ok but I can see wear already and I have barely ran the truck.  Im about to give up on this truck and stick it on ebay.

 

[spankrjs 77]

Yes, a bad motor can make horrible, gear grinding noises.

I built a Wild Willy 2 for one of my nephews a few years ago, and he drives it almost everyday. Anyway, he brings it back to me this past Christmas to repair. Sounded like a bad gear. So, I pulled it all to pieces, cleaned out the gear box, no damage. Put all new bearings in, put it back together, sounded horrible. I finally pulled out the motor, hooked it straight up to a battery, the motor was toast. A new 540 fixed it up.

I have a Big Bear project, need to get back to work on it. Yours looks great 

 

One thing I did to my gear box, you might want to try, I installed ball bearings instead of the bushings. This should help improve things. Here is a link to how I did it, no machining necessary:

http://www.tamiyaclub.com/showroom_model.asp?cid=128726

 

Even after painting the "printed" parts the stickers don't stick down well??

[Macinnis 226]

The stickers stick better than unpainted but still not great.  If I keep this thing I will try another coat of paint on the lenses.

[Macinnis 226]

Out of desperation to make my Big Bear a daily driver, and stress over this awful differential, I was wondering - Has anyone every looked into retro-fitting a Grasshopper gearbox onto the Big Bear rear arms?  I read a brief post about it on scale 4x4 forums.  They said it was possible but I couldn't find a lot of info. It looks like a grasshopper rear end parts tree is about $15 and the gears are another 10-15. This would let the truck be drive able until you guys can talk MIP into re running the Ball Diff.

[yogi-bear 2321]

21 hours ago, Macinnis said:

Out of desperation to make my Big Bear a daily driver, and stress over this awful differential, I was wondering - Has anyone every looked into retro-fitting a Grasshopper gearbox onto the Big Bear rear arms?  I read a brief post about it on scale 4x4 forums.  They said it was possible but I couldn't find a lot of info. It looks like a grasshopper rear end parts tree is about $15 and the gears are another 10-15. This would let the truck be drive able until you guys can talk MIP into re running the Ball Diff.

I've been thinking about this and its a pretty cool idea, as it allows you to make it a reasonable robust runner then. I'm guessing you still use the Mauri swing arms, maybe drill out the hubs a little to fit over the axles of the grasshopper gearbox? The trick would be I'm making sure the grasshopper gearbox doesn't rotate in hubs.

[Macinnis 226]

56 minutes ago, yogi-bear said:

I've been thinking about this and its a pretty cool idea, as it allows you to make it a reasonable robust runner then. I'm guessing you still use the Mauri swing arms, maybe drill out the hubs a little to fit over the axles of the grasshopper gearbox? The trick would be I'm making sure the grasshopper gearbox doesn't rotate in hubs.

I was thinking about that too. Keeping the axel from rotating.  As big bear rear arms are not cheap I think it would be better to modify the grasshopper axels to fit.  Some custom tubes or sleeves and bolt them to existing holes in the big bear. That is if the axels will fit through the BB arm hubs.  I need to pick up a metric caliper so someone with a GH can help see if it will fit.  Bolt the GH rear end through one or both of those slots in the BB below the "shocks"  I use the term shocks loosely 

[yogi-bear 2321]

I've got two Big Bears to build and I wanted one as a runner, so I'm tempted to give this a go, it'll be much more robust than the existing setup. 

Luckily I've got both spare grasshopper and Marui Big Bear diffs to play around with. Except I might end up machining a new set of swing arms instead of cannibalising a genuine set.

[Macinnis 226]

23 minutes ago, yogi-bear said:

I've got two Big Bears to build and I wanted one as a runner, so I'm tempted to give this a go, it'll be much more robust than the existing setup. 

Luckily I've got both spare grasshopper and Marui Big Bear diffs to play around with. Except I might end up machining a new set of swing arms instead of cannibalising a genuine set.

Check and see how the Grasshopper rear end fits in the BB arm and post a pic if you get a chance

[yogi-bear 2321]

19 hours ago, Macinnis said:

Check and see how the Grasshopper rear end fits in the BB arm and post a pic if you get a chance

will do, give me a day or two and I'll post as detail pics as I can.

[Macinnis 226]

The shapeway body mount fit flawlessly.  Being able to 3D print them dropped the price on eBay significantly.  While I had the truck on the table input the fresh 540 motor from my bush devil in and I replaced the v1 bevel gears with my smaller version 2 to see if that was my slipping problem.  Sadly, I drove the truck down the hallway at slow speed and when I turned around and as soon as I hit the throttle half way it sat and made a grinding noise. Let the gear settle and took off slowly and ran it back to the work area. Sigh 😔 I guess I stripped the stupid expensive differential gear I bought. It looks like it still has 75% of its tooth depth. It looks like it "should" work but sadly it proved me wrong. 

[yogi-bear 2321]

thats a shame about the diff. 

Apologies for the delay too, I'll have those grasshopper diff pics and measurements for you tomorrow too. It'll be 42C tomorrow, so I'll be staying indoors and catching up on a few things. Glad I have aircon!

[yogi-bear 2321]

ok, here are some comparison photos of a big bear diff and one from a grasshopper/hornet. I think can be made to work, but you'd want to make new arms and reverse mount the grasshopper gearbox.

 

 

this is where the grasshopper would need to sit to keep the same distance of the axle to the chassis.

[Macinnis 226]

I don't think I have the means to reconfigure that grasshopper axel to fit.  That is probably a lost cause for me.  I do hope some more members of this forum who are good with differential gears will read this post.  I took some close up shots of my differential at various angles.  First off to avoid confusion, I am using a combination of V1 diff gear with V2 improved bevel gears and the truck ran well like this, when it ran.  It was too powerful with the complete v1 assembly and seemed to stress everything.  The problem persists which ever assembly I use.  I assembled it on both sides and took close up shots as well as a side view of the differential gear.  As you can see on the side shot there is a very small spot on the bottom side of the differential where it looks like the idler gear was slipping up and not making good contact with the diff gear causing some wear.  My problem is, at low speed, the truck does fine.  A little gear box whine but it moves around fine.  As soon as there is any load on the gearbox it starts grinding and slipping.  It looks to me like the gears are all tight and mesh well so I don't understand where the slip in gears is coming from.  I thought about using a very thin washer to force the idler gear to stay tight to the metal heat sink plate.  My only thought is that the idler gear is sliding up at high speed and spinning off the worn part of the diff.

 

Any Thoughts?

[yogi-bear 2321]

I'd had a similar issue with my Wild One and shimming help, so its probably worth a try and you've not got anything to lose. 

If you can wait a couple of months, I'd like to give the grasshopper gearbox conversion ago. Like you I'd like a runner as well, but not keen on potentially destroying the diff if thats going to be expensive to fix. Now that I know my cnc machine will handle aluminium ok, I should be able to machine new swing arms and some sort of bracket for the suspension. But first I've got to finish of my Ford Escort project.