Ultima LWB

[XLR8]

Kyosho tires removed, wheels cleaned and a fresh set of Bow-ties mounted and ready to go.
I'm trying a different set of springs; Kyosho blacks (rears are .039" wire, 12.5 coils) - a little softer than those AE silvers. These might be too soft but we shall see.
We had storms roll through here over the weekend and drop a ton of rain. Just waiting for the track to dry - low spots are far too muddy to drive on.

[XLR8]

Well those softer springs seem to be just what the doctor ordered.
The car is very stable and predictable over the roughs and jumps.
Now, I need to focus on reducing under-steer and the car's tendency to wheelie.
I think a little weight added to front might address both problems.
It's a shame that I no longer compete - I think I could be competitive with this car.

[coxbros1]

What motor/esc combo u rockin?

[XLR8]

What motor/esc combo u rockin?

Well I have a Castle 4600kV/Sidewinder 3 that I was planning to run once I have the suspension sorted out. At the moment, I'm only running the Reedy 3300kV/SC450BL that I borrowed from my B4.1. Honestly, I think the 3300 is plenty fast so I'll probably just stick with that. The car is fairly light and my track is small. Also, despite fitting it with a full set of NIB gears, the gear box is very noisy and I'm not sure it will handle a hotter motor. I pulled the cover last night to check everything and the pinion on the plastic spur gear cluster is looking really bad - like it's been running hot - and I'd only ran 4 packs. I may end up swapping the vintage gear box for a new re-re one since they have metal gears. Original gears for these cars are very expensive.

[coxbros1]

I agree, if your gonna run it, the rere gear box with slipper will handle anything u can put to it!

[adam lancia]

Thank you orangemazda!!
I agree, it's really hard to make a separate nose plate look nice - there's always going to be a step.
I was considering making the main chassis plate one-piece from aluminum but I'm more concerned about keeping the weight down than aesthetics.
Of course, a molded carbon chassis plate would be awesome but it's not in the budget.

I just read through your whole build, great job!

To your point of designing in lightness, making the chassis out of aluminum to better accept the nose plate wouldn't be a bad thing. It would be good weight (low CG), you could get a nice smooth transition in that area, and you could machine in some pockets in the rear and leave the front full thickness to redistribute the weight. You're already cutting all kinds of weight going with a LiPo, and if you get a Lethal Weapon, you'll save a little more weight again. Points to ponder

[XLR8]

Thank you Adam and I agree. I haven't weighed the car but it seems very light - maybe too light. If I were starting the project over, I would make the entire chassis plate from aluminum.
I haven't had the car on the track since my last post. The original (plastic) spur gear cluster isn't handling the power well so my plan is to swap transmissions with my re-re Ultima shelfer. The re-re diff assembly alone is a chunk so that will definitely add some weight - unfortunately to the wrong end of the car. I could go with some stick-on weights up front to restore some balance and keep the front tires planted.
Anyway, too many projects, too little time.
Thanks for checking out the build.

[adam lancia]

The power handling part of the equation definitely makes it tricky, however, I'm willing to bet adapting a newer 3 gear trans would be well within your skillset. Not to mention, I'd really enjoy seeing what you come up with. I have a Legal Weapon that I'm going to try and make work but I don't know if it'll handle brushless torque, even with the slipper.

[XLR8]

I think I’ve found a solution to my gearbox problem that doesn’t require harvesting parts from my re-re Ultima.
The design centers upon a large 14-tooth steel pinion made for a 5mm shaft that I’ve had rolling around in a parts box for a while.

The main shaft, idler gear shaft, motor plate and cases are scratch-made, spur and slipper parts and gear cover are B4 and the rest of the transmission is vintage Ultima.

Sorry for the blurry image.

The resulting gear box assembly deletes the plastic spur gear cluster (which was going to fail), incorporates a slipper clutch, and is probably much closer to the weight of the original gear box than the re-re; with its massive metal differential assembly. The ratio is 2.64:1. Since the spur gear size is no longer fixed, I'll also have a much greater range of final gear ratios from which to choose.

I've made two case sets and the better one was painted matte black and installed in the car.

I’ve ran the car for about 40 minutes total this afternoon on a damp, high bite track and it seems good.
Having a metal main shaft gear and idler gear should make for a more reliable unit. The plastic diff gear has been holding up fine.

[Mr. ED]

top job!

[coxbros1]

You could put that into production!

[Dadio]

Very nicely done !

[adam lancia]

Damn!!! Now that's what I"m talking about! Excellent work!

[XLR8]

Thanks everyone.
I'll pull it apart for inspection after I've ran a few more packs. I especially want to check those grub screws.
I'm really happy to have this car back on the track. It's one of my favorite runners.

[radioactivity]

Hi Doug

Being a total Kyosho noob ( aka AE snob) I have tried to learn how the original trans was set up.
It seems as though better than half of the gear train resides outside the case and under the gear cover with no slipper.
Only the top shaft and ball diff were in the trans?

TU trans.JPG (37 KiB) Viewed 1192 times

TU trans.JPG (37 KiB) Viewed 1192 times

If so, what an improvement!

Chuck