Possible motor problem with Bachmann Lyn

Greg Elmassian said:
i'm pretty sure you cannot edit a post to remove all text, see if you can put in a number of blanks/spaces
Click to expand...
You can delete all the text, Greg, but the posy stays there blank.

If it's an original posting, then as long as you don't press the 'post reply' button, it'll eventually disappear.

I'm not sure how it works if you are trying to edit a post that has already been posted ...... if you get my drift.
 
Yes, I think that is what I said! ;)

I'm confused here, between editing a post, and the text left over in the "post reply" box...

It almost seems like you are talking about both in the same post??

I've had the "leftover" text in the "post reply" box last for weeks some times... it is linked to that particular thread... so I do put blanks in it right away to stop from posting junk accidentally
 
Well, a bit more progress.....

After considerable internet searching, contacting a couple of gear manufacturers and even discussing the problem with Bachmann, I've ended up buying a worm and worm wheel from China. They are not ideal, but the nearest I could find to what's needed. The worm has a 3mm bore (the Bachmann motor shaft is 2.5mm) and the bore of the worm wheel is 6mm ( the Bachmann nylon 'axle' is around 8mm).

I used a piece of 3mm copper tube reamed out to 2.4mm to enable the worm to be forced on to the motor shaft. I 'removed' the nylon gear from the axle, and turned it down to about 7.6mm by putting it in the chuck on my drill and applying a flat file while it rotated. I then opened out the hole in the worm wheel to 7.5mm and forced it on to the axle.

The motor block was redesigned to lower the motor nearer to the axle. It nearly works! It goes all right in one direction but the gears grind horribly in the opposite direction. So, have raised the motor by 0.2mm. The new motor block is now printing - it takes 16.5 hours to print, so will have to wait and see if that cures it .... If not, I'll have another go!

new block-merged.jpg

Rik
 
Looks like the worm needs to be further away from the motor to get better engagement...

I'm curious, what happended to this? It sure looked successful...

414470_Motor_block_x_3.jpg
 
ge_rik said:
Well, a bit more progress.....

After considerable internet searching, contacting a couple of gear manufacturers and even discussing the problem with Bachmann, I've ended up buying a worm and worm wheel from China. They are not ideal, but the nearest I could find to what's needed. The worm has a 3mm bore (the Bachmann motor shaft is 2.5mm) and the bore of the worm wheel is 6mm ( the Bachmann nylon 'axle' is around 8mm).

I used a piece of 3mm copper tube reamed out to 2.4mm to enable the worm to be forced on to the motor shaft. I 'removed' the nylon gear from the axle, and turned it down to about 7.6mm by putting it in the chuck on my drill and applying a flat file while it rotated. I then opened out the hole in the worm wheel to 7.5mm and forced it on to the axle.

The motor block was redesigned to lower the motor nearer to the axle. It nearly works! It goes all right in one direction but the gears grind horribly in the opposite direction. So, have raised the motor by 0.2mm. The new motor block is now printing - it takes 16.5 hours to print, so will have to wait and see if that cures it .... If not, I'll have another go!

View attachment 284655

Rik
Click to expand...
That doesn't look to be the gear to go with that worm - the pitch of the gear looks different to the pitch of the worm - in my eyes :think::think:
 
I think it might be shadow creating an illusion?

But the supplier might be inscrutable! :mask:
 
Greg Elmassian said:
So asking the question a 3rd time, I hope more clearly:

Did you need to change the gear ratio for pulling power? (The big worms worked but wrong gear ratio?)

Greg
Click to expand...
No, the increased gear ratio provided with the larger worm wheel is just an added bonus.

The problem I've been trying to overcome is the loss of power transmission produced by the large diameter of the old worms. As Jimmy says, it's to do with the moment of inertia (aka rotational inertia). Think of a skater spinning round on the ice. If she spreads her arms out she spins more slowly, if she brings them in closer to her body, she spins faster. The larger worms require more effort from the motor to turn the worm wheel than smaller diameter worms. This is why the old mechanism lacked power (and the motor overheated).

Rik
 
ge_rik said:
No, the increased gear ratio provided with the larger worm wheel is just an added bonus.

The problem I've been trying to overcome is the loss of power transmission produced by the large diameter of the old worms. As Jimmy says, it's to do with the moment of inertia (aka rotational inertia). Think of a skater spinning round on the ice. If she spreads her arms out she spins more slowly, if she brings them in closer to her body, she spins faster. The larger worms require more effort from the motor to turn the worm wheel than smaller diameter worms. This is why the old mechanism lacked power (and the motor overheated).

Rik
Click to expand...
I get the theory, but it surprises me that it actually makes a difference in our scale - large as it is.
 
I don't think it has anything to do with the condition of the motor. Through various means, I now have three of those motor blocks and they all perform in exactly the same way even though one has a Buhler motor in place of the Bachmann original. The only common factor is the size of the worms.

The formula for calculating rotational inertia indicates that the force is proportional to the distance from the axis of rotation squared! So even in our scale, increasing the diameter of the worm has an exponential effect on the force needed to turn it. Doubling it, requires four times the force, tripling it requires nine times the amount of effort and so on. The larger old worm is roughly three times the diameter of the new worm and so, I reckon it will only require a ninth of the effort needed to turn the new worm.

If anyone wants to check my maths then please feel free to do so.

This could explain why Bachmann redesigned the Lyn mechanism - it now has a single small diameter worm gear.

Rik
 
Last edited:
PS I have just acquired a fourth Lyn motor block thanks to the generosity of a fellow forumite. This block is the newer version with a single small worm. Incidentally, the motor powering it is identical to the original.

The problem is that the motor on the new block has had it. One of the brushes has disintegrated and as it's a can motor, I can't get inside to replace it. I do, however, have identical motors from the old motor blocks but I can't get the worm and flywheel off the motor on the new block. I've bent one gear puller and even a new heavier duty puller just won't budge it. I've tried heating up the worm and flywheel but they still won't budge.

Does anyone have any suggestions?

Rik
 
You must log in or register to reply here.
Back
Top