Frog Brat Diff Mod

[Corona Powered]

I am currently working on strengthening the frog/brat gearbox. I am using TC member "oldfrogshot" method for strengthening the diff, located in this posting: http://www.tamiyaclub.com/showroom_model.a...74&sid=3142

The kit that I have is one of the new re-issue kits, which has the new diff drive cups. One of the cups has a hardened locating pin which must be removed, then drilled and tapped. Oldfrogshot's method requires tapping the two ends with a 2.5mm tap. I have completed all steps, but I can't find a 2.5 x 25mm screw. Does anyone have a source for such tiny metric hardware?

I have been able to find a 2.5 x 20mm screw, but it is not long enough to fully engage.

Thanks.

[bakaguyjean]

Check your LHS that has RC cars,and see if they have a ball diff rebuild kit for just about anything. There should be a bolt in one of the kits that would work. I just hope the bolt holds up.

[Blacque Jacque]

I had to buy a bag of 50 to get that size, not cheap either, at over 10 with postage, but they are A2 stainless & I guess I'll never need any more .

I got them from here:

Precision Technology Supplies

[markbt73]

There's no reason it has to be metric, either... if you're in the US, look for a 2-56 or 4-40 tap and a 1 inch screw. Easy to find at hobby shops; Du-Bro sells bags of 4 of most hardware like that.

[homerboi]

Corona,

You can purchase these screws by the piece at home depot or lowes. Goto the hardware bolts screws aisle. They should have them in either small bags of 4-8 pieces or individuall. My local home depot sells them individually along with other size screws and bolts.

As markbt73 stated, they dont have to be metric size.

[TAZ-NZ]

Oldfrogshot's method requires tapping the two ends with a 2.5mm tap.

The Oldfrogshot mod only requires you to tap one of the drive cups, the other drive cup you need to drill out so that it spins freely on the screw, it's also a good idea to countersink the untapped drive cup to accept the head of the screw. When assembling the diff, apply diff grease to countsink hole in the drive cup and the head of the screw, this allows it to spin more freely and prevents it binding.

I've applied this mod to three sets of re-release Frog axles, two sets for the dog bone axles and one set of the universal axles, I've also got a custom set of axles with this mod, made by Oldfrogshot himself using TA04 drive cups. It's a great mod, but it takes a little tweaking to the screw just right, too loose and it doesn't do anything, too tight and you end up locking the diff. Get it right and you can abuse the diff no end and it will just take it.

Make sure you give the locktight on the screw thread a full 24 hours to set hard, otherwise the screw tends to break loose.

[dollarlongnecks]

This is the exact thing I have been doing for the last week. I have been running all over town trying to find 2.5mm taps and screws. Ruined one cup already by trying to counter-sink the hole to accomidate a 20mm pan head and drilling it too deep. After looking around at ACE Hardware, I realized that a 4-40 was just barely bigger and was easy to find. Works like a charm.

The only problems I'm having with this re-re frog is the front axles. Broke them both off this weekend...

[TAZ-NZ]

The only problems I'm having with this re-re frog is the front axles. Broke them both off this weekend...

Seems to be an issue for the re-release Frog/Brat items. http://www.tamiyaclub.com/forum/index.php?showtopic=29761

[billg4]

swap out the front to traxxas stampede parts and run TLT tires and rims like I did

not hard, pede front upright trimmed just a bit and it fits in the

frog/brat arm piece. A few spacers to go between the tierod and arm and bingo.

The 1150 rpm stampede parts may fit as well but these traxxas parts were 3 bucks.

[TAZ-NZ]

swap out the front to traxxas stampede parts and run TLT tires and rims like I did

not hard, pede front upright trimmed just a bit and it fits in the

frog/brat arm piece. A few spacers to go between the tierod and arm and bingo.

The 1150 rpm stampede parts may fit as well but these traxxas parts were 3 bucks.

Billg4 love the franken-brat, there'd got to be parts from a half dozen different kits in there.

TLT Wheels

Stampede uprights,

brat swing arms and front body post.

mudblaster rear body posts & rear shocks

King blackfoot chassis unless it's just painted black

blackfoot battery door/ holders.

Glad I'm not the only one that uses parts from any compatible kit.

[billg4]

it is a bit of everything I guess

Built from a box of ''spares'' all the way except for radio gear and the stampede uprights.

Oh, and thanks, FRANKEN' BRAT sounds just perfect

[Corona Powered]

Thanks everyone who replied to this thread. Lots of great ideas. I basically have given up on finding 2.5x25mm screws. I did find 3x25mm screws in stainless at Ace Hardware though. So I'll have to drill the hole out slightly and get a new tap. No big deal, there appears to be enough material there. The new thing that's giving me a headache is finding front shocks that fit this thing. I purchased the CRP front mounts, but can't find a good shock to fit (the CRP shocks are no longer available). The SRB front shocks are too short. The SRB rear shocks are too long. I also tried the front shocks off my Turbo Optima Mid - those were too long with not enough travel. Someone had also suggested Lost Mini-T shocks - too short and too flimsy (very thin shock shafts). Any ideas? There is a thread going on Frog front shocks, guess I'll post up there and see. Or make my own front shock mounts. Thanks again.

[homerboi]

Corona,

I have red crp shock mounts on my frog and use a set of the SRB front shock with the crp shock upgrade kit.

Im pretty sure 60mm shocks will fit the build you're looking for.

try fleabay seller yeostore. I believe he has a set of 60mm dampers that should work. cheap too!

alternatively, you can try using a set of TC3 threaded dampers. If I recall, these are just slightly shorter but you can unthread a few turns the bottom ball end to lengthen it. As for it's shock body diameter, I know its much wider (12mm vs 8mm for teh SRB) but I think you can compensate by add a spacers at top and bottom end of the shock mounts to fit.

Just my 2 cents.

[Corona Powered]

Thanks Homerboi.

For the badword of it, I threw on my set of SRB front shocks equipped with a vintage CRP coil over conversion. They fit almost perfect - they are probably 59 or 58mm - just a mm too short. And they do fit the look of a vintage buggy perfectly. They're just such an old design, and they don't have much oil capacity. And since this is my runner (it's a re-issue), I'm going for performance.

I think a modern shock design would be better, but you are right, they'll need to be spaced out a bit further because of the larger diameter shock body.

[homerboi]

To space out the larger diameter shocks away from the crp shock mount try using the spacers for the shock rods you find on the tamiya shock trees or similar. They're about 3-5mm which works fine for the spacing required.

I also forgot to mention that with the vintage SRB shocks, if you do use them, you may want to turn them upsidedown when mounting them - they're known to leak. I've tested them with 30wt silicon oil and it seems ok. Maybe a heavier weight oil may leak less?