The Official Armortek Forum - World leader in one sixth scale metal kits

Just starting to look like a tank.

Paint arriving this week.

Looking good! We are both in about the same place. Primed hull, bare decks and turret.

But I see you have welds going on. Haven't gotten that far yet.

I would appreciate some advice from you guys please.

I’m having trouble with the sprocket taper bush.

On my kit the grub screw will barely go into the release hole - it will only enter a couple of turns.

The hole on the bush itself has a thread all the way down. The corresponding half hole on the sprocket has no thread and the combined hole is nowhere near big enough to take the grub screw.

I have gradually filed the sprocket half hole so that with a huge amount of torque I can just about get the grub screw into the hole but it will not bottom out and start to drive out the taper.

Do I just keep on filing until it does lift the taper or is there something I am missing?


Many thanks again

Hi Michael

Would it be worth posting a couple of photos?

Regards

Charles

Charles A Stewart wrote: ↑

Thu Jul 13, 2023 7:29 pm

Hi Michael

Would it be worth posting a couple of photos?

Regards

Charles

Charles


I will try and post a couple tomorrow but as it’s my birthday they might not be as informative as they should be.

Thanks for the response

Charles


Do these help at all?

Having trouble with posting pictures at the moment

If the last picture posted is your sprocket, and it has been taken off the final drive shaft, Not sure what your trying to achieve
If you want to remove the taper lock, just remove the grub screw and gently tap out the taper lock out from the other side.
(Taper locks are usually hard and brittle, don't drop them)
The taper lock has to be perfectly aligned with the half treads on the sprocket to work correctly. Otherwise grub screws can become tight or jam in the threads.
This maybe the problem.

The releasing half slot milled into the sprocket may not be correct depth and as you say it needs to be relieved.

Or, I know it's the bleeding obvious, but you are using the correct size grub screw, usually they are same size as the locking grub screws. check that the grub screw fits the locking treads on the taper lock.

Are there threads on the taper lock?

Old joke, chuck a similar looking BA bolt into the workshop box of metric bolts, and wait almost as funny as a nut without threads.

John

Thanks for your input

I am just trying to make sure that the taper will be able to be removed with the grub screw if it is required in the future prior to fitting the sprocket. I confirm that the grub screws are as supplied. There is a thread on the taper but not on the sprocket.

At the moment no amount of torque will entice the taper to lift from the sprocket even without it being fitted to the drive shaft.

I would be interested to know if anyone has successfully tried removing the tapers with the grub screw as at the moment I cannot see how the system works.

Really appreciate your input - many thanks

Hi Michael

The ejection hole is not intended to be threaded. It's machined oversize of the 1/4" BSW grubs.

Your issue could be that the taper needs to have the drive shaft on its internal diameter to function correctly. If tightly pressed into the tapered bore without the drive shaft to form to, it can over compress. Putting the grub in the exit hole will just compress it further.

Hope this helps.

I've not tried this action myself before, (pushing the taper lock hard in the taper without the shaft), normally just loose, a sizing check.

In some respects plausible Sean, but I would expect the grub screw to screw down the release thread however tight the taper is unless it's deformed or out of alignment.

Can I ask Michael, if the grub screws fit in the locking treads ok? They should all fit if properly aligned.

There are two other possibility you may not like.
The taper has been spinning in the sprocket and has worn an over sized taper in the alloy sprocket (Bad) and nothing will fit very well again.
(I should say unlikely because the locking grub screws would have been left out)
or
If the taper lock has been tightened hard in the sprocket without the center shaft in position. All the force of the taper lock has been exerted only on the alloy sprocket and not evenly against the steel shaft.

The Picture doesn't really show any distortion and the taper lock split gap has not closed. But if it were me, I'd try the taper lock with the sprocket and the output shaft, all three treads should be aligned with their corresponding slots and a grub screws should fit in all three threads easily.
If so, try tightening up (remembering to remove the loosing grub screw) You don't have to go "full welly" on tightening up.

Remove the locking grub screws and then check if the release grub screw works as it should. If so all good.

If not the problem lies elsewhere, Try another taper lock. Their not expensive (a few quid) and the details should if your lucky be on the taper lock.

If that's ok, the fault is with the machining of the Sprocket taper.

[media]

[/media]The ejection hole is not intended to be threaded. It's machined oversize of the 1/4" BSW grubs.

Your issue could be that the taper needs to have the drive shaft on its internal diameter to function correctly. If tightly pressed into the tapered bore without the drive shaft to form to, it can over compress. Putting the grub in the exit hole will just compress it further.

Sean


I have attached a picture of the other sprocket that I have not changed at all. The installation is fine as the grub screws fit the threaded hole. The removal hole will not entertain the grub screw at all - it will not go in. I cannot see how this is an oversize hole. On the other sprocket I have tried lightly filing out the hole in the sprocket side and the grub screw will now go in but it does not force the taper off the shaft. I am very reticent to commit to fitting these tapers if I have no method of removing them in the future.

Pictures are an issue as I have recently had to change email providers and I cannot work out how to reduce file size yet

John


Many thanks for your efforts.

I have followed all suggestions to no avail.

I’ve asked AM to send me two new tapers to see if that solves the issue.

I’ll let you know if I get anywhere with it.

Have a great weekend.

Mick

Hopefully before you order new taper locks, I thought I'd pull out one of my brand new painted sprockets to see what's what with a brand new taper lock.

The removal grub screw will quite easily screw in and out with a socket tool with just the fingers. Which is what I would expect. the locking grub screws the same.

Looking at your last picture there is evidence that some force has been exerted on the edge of the taper lock removal thread. This would indicate either the thread is very tight as the grub screw try's to pull inwards or the hole is just not big enough.

Sean is right about the 1/4" BSW grub screws. M6 grub screws look similar but have a finer thread. So make sure the the BSW grub screws are being used.

So if you have the right grub screws and there's no obvious fault on the taper lock. All that's left is that the removal slot cut (arrowed) on the sprocket has not been machined with enough depth and width.

I'm guessing there's not a lot of material in the slot to remove, As long as the taper is ok, a bit of grinding / filing should solve the problem.

It happens

Just took another picture after the grub screw and taper lock removed from my Chieftain sprocket. You can see the grub screw has rubbed the edge of the machined slot. it's a tight tolerance.

This is not enough to jam the grub screw, so it should be quite able to draw the taper lock loose as it should.

A little polishing out of your slots and you should be ok hopefully.

Hope all this helps.