Kol's Optima Mid

[toyolien]

20 minutes ago, Kol__ said:

Thanks mate. To clarify we're talking about the Kyosho OT227B belt? Cheers

Yes, this is the one, but I think the 'B' revision is the newest variant.

 

[Kol__]

16 minutes ago, Grumpy pants said:

Nice family outing, wife and kids all involved 👍

T'was indeed buddy, thanks. On the occasions when an RC comes with us, the wife's pretty good at putting up with these shenanigans generally. I just have to keep in mind not to get too engrossed in blasting the buggy around, as these sort of walks are a family afair at heart. The kids wanted to drive this one, but imagining the pain of seeing more than a £400 (with the mods) buggy being driven full pelt into the trunk of a large tree or some sort of similar disaster, I opted not to entertain quite that approach. Instead, I allowed them control of the steering only, whilst I controlled the speed. To be fair they loved it and that was enough for them😁 If we'd been in a wide open area, I'd have let them have a run as I normally do though. And they have their own buggies now anyway🤠

[Kol__]

12 minutes ago, toyolien said:

Yes, this is the one, but I think the 'B' revision is the newest variant.

 

Nice one mate. I think the Mid geared diff internals are now finally available again at one of the usual overseas haunts, so I'll add one of these belts to the order👍👍

[Sgt.Speirs]

@Kol__: Nice buggy and great shots!🥰

Looks like you had a lot of fun.

[Kol__]

3 hours ago, Sgt.Speirs said:

@Kol__: Nice buggy and great shots!🥰

Looks like you had a lot of fun.

Thanks my friend, it was a good way to start the season!😁

[Andreas W]

Happy to see you are enjoying the gorgeous Optima Mid. Looking forward to build mine sometime next year. I am debating back and forth if I should get hear diffs for it or not. 

[Kol__]

On 5/1/2025 at 9:06 AM, Andreas W said:

Happy to see you are enjoying the gorgeous Optima Mid. Looking forward to build mine sometime next year. I am debating back and forth if I should get hear diffs for it or not. 

Thanks bud. I'll update on any changes in performance from the ball diffs to gear diffs.

The buggy has only had the two runs so far, so another run on the ball diffs, then I'll check if any adjustments are needed, and decide if it it's time to swap out to the geared diffs. Either way I'll be going with the shorter Optima belt at that point.

[Kol__]

To update, I managed to get out and run the Mid for the 3rd time today...

However, it's starting making awful racket now, there is a real clatter to the drive train. I first noticed it doing it when I jumped the buggy today and could hear the noise very clearly as it free wheeled in the air over the jump. Captured it pretty clearly in the vid below I reckon. I'm going to check the pinion first. Other than that I suspect it's the rear ball diff, possibly the casing where I've seen reports of the plastic teeth being ripped up.

What are your thoughts on the cause of this noise guys?

https://i.imgur.com/RVogCDg.mp4

[toyolien]

Sounds to me like it could be the pinion or spur rubbing on the plastic gear cover. It happened to mine. Take the gear cover off, and try it again. I ended up getting a penguin rc lexan cover instead.

[Kol__]

14 hours ago, toyolien said:

Sounds to me like it could be the pinion or spur rubbing on the plastic gear cover. It happened to mine. Take the gear cover off, and try it again. I ended up getting a penguin rc lexan cover instead.

Ah I see, thanks mate, will check that out. So have Kyosho just not allowed enough clearance under the cover then?

[toyolien]

I can't quite remember where mine rubbed, but I think it was the slipper lock nut rubbing on the cover. Let me know if that's what yours is doing 👍

[Pieter45]

I had the same problem, allready after the second run.

It turned out that main gear was completely stripped. I'm not sure why, but I guess that my belt-tension was to high. (Using the shorter belt of the Optima.)

[Kol__]

29 minutes ago, Pieter45 said:

I had the same problem, allready after the second run.

It turned out that main gear was completely stripped. I'm not sure why, but I guess that my belt-tension was to high. (Using the shorter belt of the Optima.)

This is what I suspect from what I've seen online. Is it the rear ball diff gear main case that's has the teeth stripped from it?

Have you been running yours much @toyolien?

[toyolien]

34 minutes ago, Kol__ said:

Have you been running yours much @toyolien?

A fair bit. It's done an outdoor race on Grass at Batley, the Modelsport Vintage National at Worksop and three single day race meets at a local (ish club). I also use it at a local car park just for fun. I really enjoy driving it. The Optima Mid was the first car I ever saw racing back in 1987/8 at a town Carnival. There was a local car club (which only closed two years ago) that put on a display on the Carnival ground. Although I didn't know it at the time, I witnessed a close race between an Optima Mid and a CAT XLS. I later learned what they were from a magazine I bought. So, the Mid has a special place in my fleet! 

[Pieter45]

11 hours ago, Kol__ said:

This is what I suspect from what I've seen online. Is it the rear ball diff gear main case that's has the teeth stripped from it

Yes, it was.

It was completely stripped, hardly any teeth left.

I was running it on the beach, with a kind of hard "grass" which came between the axles, probably causing too much friction. 

Hope you understand, English is not my native language.