Javelin Belt Tension

[Ty89m]

For those with Optima/Javelin build who opted to run the belt, could you do quite a bit of fore/aft movement of the front assembly to tension the belt? Try as I might, I can barely get movement on mine, and nowhere near the available given by the slots in the front skid-plate/side plates (where you use the serrated washers to lock things down). The design makes it seem like you should get a few mm of adjustment, so I wonder if I goofed somewhere - specifically on the little plastic channels where the belt rides on top/bottom.

Anyway, if anyone has recently adjusted the belt on an Optima/Javelin, I'd be curious if you noticed the same.

Thanks.

[markbt73]

You don't actually want any tension on it, just take up the slack. Tensioning the belt will add drag, and it's hard on the bearings. As long as it doesn't skip under acceleration, it's fine.

The adjustment slots are a holdover from the chain drive days, which tended to stretch and require a little adjustment (or taking out a link).

[Ty89m]

5 hours ago, markbt73 said:

You don't actually want any tension on it, just take up the slack. Tensioning the belt will add drag, and it's hard on the bearings. As long as it doesn't skip under acceleration, it's fine.

The adjustment slots are a holdover from the chain drive days, which tended to stretch and require a little adjustment (or taking out a link).

That would explain why the manual only mentions chain adjustment in step 40 - with no mention of belt tension. Thank you.

[Kai City RC]

Interestingly, in the re-release Optima Pro manual there is a section on setting the belt tension. It says the weight of the buggy (without battery) when held vertically by the bumper is the correct tension for the belt. The Optima Pro manual can be downloaded from the Kyosho homepage. 👍

[Hobbimaster]

17 hours ago, Kai City RC said:

Interestingly, in the re-release Optima Pro manual there is a section on setting the belt tension. It says the weight of the buggy (without battery) when held vertically by the bumper is the correct tension for the belt. The Optima Pro manual can be downloaded from the Kyosho homepage. 👍

If I'm not mistaken, doesn't the Optima pro have the Optima mid belt that is one tooth longer? It may be a bit more critical to adjust, and tension than the regular Javelin/Optima kits.

[Ty89m]

On 8/9/2024 at 11:15 PM, Kai City RC said:

Interestingly, in the re-release Optima Pro manual there is a section on setting the belt tension. It says the weight of the buggy (without battery) when held vertically by the bumper is the correct tension for the belt. The Optima Pro manual can be downloaded from the Kyosho homepage. 👍

That's the same rule-of-thumb we use to tension the tail belts on helis. Also, I think I have you to blame for my new re-release buggy addiction. Your videos have been very informative.

There seems to be enough tension on the belt (without intentionally adding more by pulling on the front assembly) that it doesn't lay flat against the belt channels. If it skips under use, I'll try the Optima Pro trick.

[Kai City RC]

On 8/11/2024 at 7:32 AM, Hobbimaster said:

If I'm not mistaken, doesn't the Optima pro have the Optima mid belt that is one tooth longer? It may be a bit more critical to adjust, and tension than the regular Javelin/Optima kits.

That is correct, the low friction belt used in the Optima Mid (and now Optima Pro) is slightly longer.

[Kai City RC]

On 8/12/2024 at 1:47 AM, Ty89m said:

That's the same rule-of-thumb we use to tension the tail belts on helis. Also, I think I have you to blame for my new re-release buggy addiction. Your videos have been very informative.

There seems to be enough tension on the belt (without intentionally adding more by pulling on the front assembly) that it doesn't lay flat against the belt channels. If it skips under use, I'll try the Optima Pro trick.

Thanks! I've had a few people tell me my videos are the reason they got addicted to vintage Kyosho re-releases. 🤣  Now, if only Kyosho would realize I'm acting as an ambassador for the brand and perhaps send a few perks my way! 😀