RJX XT50 FBL Head loose fit on Vibe50 10mm shaft.

[Gunnergolly]

Don't seem to be having much luck these days with my FBL heads .

The DFC head that i bought for my TRex 500 has lateral play in the feathering shaft and the RJX XT50 head i bought for my Vibe 50 has no lateral play but rocks ever so slightly on my Vibe's 50 10mm shaft ???.

Have flown my Vibe 50 seven times now with it's new RJX head and really happy with the way that it's flying.

However today out of curiosity i removed the RJX head to examine the shaft and i can see the friction marks where the RJX head is pivoting on it's Jesus bolt and also where the bottom of the RJX head is gradually cutting into the Vibes 10mm shaft..... so i've got a problem !!!!.

I bolted the RJX head onto my Raptor 50's 10mm shaft and again i found that the RJX head rocks slightly on that shaft as well.

Measured both the Vibe 50 and Raptor's shaft and they both measure bang on 10mm, so it looks like the problem is due to the tolerance of the RJX head.

Not sure what to do now but looks like i'm going to have to contact Rossmod where i purchased the head from and maybe they'll send me a replacement head block ????..

If not then i'll have to purchase another head block for £15 and hope for the best that RJX have managed to manufacturer it with the correct tolerance...


Just two questions that i have :-

1) Has anybody else bought this head (RJX XT50 Flybarless Head Assembly [FL50-1001]) and how did it fit on your 10mm shaft ?

2) Anybody know who stocks the full range of RJX FBL head spares in the UK ???, these are the only two that i can find and one i found in Ireland :-...

a) Rossmod do but most of the time they seem to be out of stock of items...

b) RJX Hobby only seem to stock some of the spares... (Flybarless).

c) RJX Flybarless Head Parts - Radio Controlled Shop

Thanks...

[Andy from Sandy]

You need to gorilla up the pinch bolts to stop the head rocking on the 10mm main shaft. I have used one and it works.

Get a complete spare head from Hobby King is an option.

[Gunnergolly]

You need to gorilla up the pinch bolts.

I have a done them up as tight as i can with my Align screw driver style Allen Keys....

But your saying that i should proper "honk" them up really really tight with a set of "long" Allen keys ...

I'd better wait and buy some good quality Allen keys before i do that as the cheap ones i have will probably round the heads out of those pinch bolts !!!

[electricsceadu]

the other option is to drill and tap the head block and fit a grub screw in oposite sides of the block (the same direction as the jesus bolt)
this will stop the rocking
the morley f1-60 used this idea
make sure the block sits square to the mainshaft or you'll have tracking issues

[Gunnergolly]

Thanks for the suggestion, trouble is that below the Jesus bolt there is no solid metal to "tap" into.

The only place that you could drill and tap is above the Jesus bolt, the distance between the center of the Jesus bolt and the top of the shaft is around 9.3mm.

I have included a couple of pictures below so that you can see what im referring to...



I think that Electricsceadu idea is a good one and i think it would also work, but i'm also a little bit worried that it may also weaken my head block ???.

Measuring across the internal hole were the shaft slides into the head block in the direction of the pinch bolts i'm getting 10mm and when measuring across the hole in the direction of the Jesus bolt it comes in at 10.3mm, so it's not even round !!!!...

Before i start doing any mods i think i will contact Rossmod and ask for a replacement head block, i haven't found any reports of this head being a loose fit elsewhere in my Google searches..... maybe i've bought a bad un !!!!...

Thanks...

[matjonze]

I had the same problem with my V50 and the RJX FBL head. Coated the top of the shaft with some proper green loctite, tightened it down and left it cure up for a few days. Never had a problem since.

[Gunnergolly]

Yeah it's a shame about this problem, as the RJX head is nicely engineered, works well with the BeastX and offers excellent value for money.

Just emailed Rossmod, will be interesting to see what they come back with....

Out of curiosity would you still be able to remove your Vibes head if you wanted to after applying Green loctite ???...... i don't suppose you have tried yet ...

[matjonze]

Yea, i usually hold the main shaft over the gas hob for a min or so to slightly heat it and then it comes off without any problems. I've had the same problem with a gen align 450 pro head block/shaft, so it's not just RJX that have this issue. When you are machining so much in bulk, tolerances can vary with tooling wear.

[Gunnergolly]

Thanks for the reply, certainly an option that's worth trying then.

I'll just hold on for now and see what Rossmod come back with, but i'm going to insist on a new head block and hopefully i'll get a good one 2nd time around.

[Gunnergolly]

To add closure to this thread, i ended up buying two more complete RJX heads from Hobbyking for £45 each and replaced my original bad fitting main head block with one of the new ones and it now fits perfectly with no rocking.

Looks like i just got unlucky with the original head block and bought from a bad production run....