HL Drive Sprocket Screws

[daviddunlop]

Started tearing down my HL Tiger I for a rebuild the other day and was quite surprised to find that as soon as I had broken the left side track to remove it, the left side drive sprocket fell off. Fortunately the screw to fasten it to the gearbox drive shaft was safely inside the sprocket assembly. I had used a bit of clear silicone sealant to hold the hub cap in place last time I had worked on it.

Made a mental note to myself that when reassembling the Tiger to be sure to put a bit of clear silicone sealant on the left side drive sprocket screw to keep it in place in the future. Seems that as the tank moves forward, the Laws of Physics are working on the left side drive sprocket screw to unwind it. And at the same time, the same laws are keeping the right side screw nice and snug.

Thought I would pass this on in case anyone has been throwing a left side drive sprocket and wondering why.

Cheers,

David

[Crispy]

I found the same thing on a new HL Tiger 1 bought recently. Left sproket felt a bit loose and once I got the cap off the screw fell out. Once I've finished moding it I'll be putting a dab of Tamiya thread lock on the screws, best stuff i've found for this and it wont damage the plastic. Smells nice too

[Miggers]

I had the same problem with my Tiger,always seemed to be the left one too

Anyway,I checked the dimensions of the HL screw,M3 thread and 7mm in length.
The HL gearbox shaft is drilled and tapped for about 12mm deep.

Off I went to our local engineering/fastening supplier and picked up some M3x10mm
cap headed set screws,some M3 stainless steel flat washers,some M3 spring washers and an
allen key to fit the cap headed set screws.

The method:

Remove the centre cap from a sprocket and take out the screw.

Take a cap headed set screw and put it on the allen key.
Next put a spring washer over the threads and then a flat washer.
Put the tiniest smear of thread locker onto the end of the set screw's threads
and fit the screw into the gearbox shaft.

The advantages:

The spring washer and dab of thread locker ensure it won't come undone by itself.
The flat washer helps to "spread" the load inside the sprocket.
The cap head screw on the allen key make it easy to put the screw back in.
No more tipping your tank on it's side and trying to line the screw up with a pair of tweezers
and risking damge to your tank or the cross head of the originl screw.

Mark

[BREL]

nice tip Mark for those that don't know

[Saxondog]

I just thought I would comment on thread locker.When building engines thread locker is applied to the upper portion of the bolt,two reasons,First if this liquid pools in the bottom of the hole it will expand under heat and push against the bolt,second if only used on the section near the head,three threads or so if you have trouble removing the bolt a little heat on the head and out it will come.As far as the sprockets go it seems that this would be the right thing to do.Small amounts of thread locker is really all that is required,and if used at the top near the head much easier to remove if heat application is needed.This is how I trained,and it is just a method that may have some relevance in this situation.

[Ex_Pat_Tanker]

I've found that a little drop of superglue is all it takes to stop a screw backing out - not too much, just a little It won't bond all that well to steel, but will make just enough crusty mess in the treads to do the job