Dapol Class 67 worm drive not engaging

[LukeB]

I've got three Dapol Class 67s and they're all a bit iffy. One, the motor blew up so is now a dummy. Another runs fine for a while but really slows down after about five minutes of running until it's cleaned again.

 

My best runner now has a problem with the drive. When pulling a load it runs fine on a straight but on a bend the friction seems to overwhelm it. The cause seems to be the worm drive at one end failing to engage with the gear tower on the bogie. The result is that the wheels at the other end are powered and spin but fail to get enough traction without the bogie at the problem end providing any drive.

 

I've swapped bogies from my other 67s around and all of them are not driven by the worm drive. It's as if the worm drive is not quite low enough. I think one of my 68s has the same problem.

 

Is there a neat way to fix this problem please?

[34theletterbetweenB&D]

On 18/01/2024 at 11:58, LukeB said:

I've swapped bogies from my other 67s around and all of them are not driven by the worm drive. It's as if the worm drive is not quite low enough. I think one of my 68s has the same problem.

 

Is there a neat way to fix this problem please?

I had a look at the Dapol class 67 mechanism diagram attached, hopefully this will correspond to what you have seen on the mechanism of the models you own.

https://cdn.shopify.com/s/files/1/0644/3971/4015/files/Class_67_Combo-compressed.pdf?v=1697702116

As the bogies are a 'push fit' to engage the worm with the bogie gear tower, and Dapol's instructions include:

"The bogies are a ‘pull out ’ & ‘push in ’ fitting method. When refitting, ensure that the gear on top of the bogie tower meshes with the worm."

this is where I would start looking.

 

The bracket which sits above the worm must engage the clips on the sides of the gear tower to hold the worm in mesh with the bogie gear. If there is any damage to the bracket such that it doesn't fully engage one or both of the clips on the bogie, the worm will lift itself off the gear when running under load, leading to the problem you describe. This is likely to need a replacement bracket if it is the cause.

 

My suggestion is that since you have a model with a  failed motor, currently a dummy, you could take a bracket out of this and use it as the replacement. (Please bear in mind that never having looked inside a Dapol N gauge model I have no idea how tricky this may be: the general principle of using a  model as a 'breaker' for spares works well for me in RTR OO of similar mechanism layout.)