Drivetrain advice

[neilkirby]

Hi All,

 

I am hoping for some advice here. I have been designing my own model of a Sentinel locomotive for a while now which is to be 3D printed. I am aware that people say that 3d print locos do not have enough weight to give them any pulling power. So I created compartments in the body wherever possible to fill with lead shot. As of this weekend I thought I had a working prototype. (See below) and after loading up with lead it does pull about 8 wagons of varying manufacture along a short test track, and looks like it could pull a few more. But it sounded awful! AdmitedIy I am using a cheap ebay motor, but this doesn't sound too bad on it own. This motor drives vertical spur gears to a leyshaft below, the layshaft is mounted on to very small roller bearings in the chassis and this shaft has a set of tenshodo worms and gears onto each axle. as a test I removed the gears from the axle and the noise is still there, so I am pretty sure its the (purchased) spur gears that are making the racket. I am no expert in this can someone tell me what the likely cause is? Is the meshing too close ? too far apart? too much play on the stub axle of the intermediate gear? Any and all advice welcome Thanks in advance.

 

I have included a quickly drawn diagram of the gears in case my description doesn't cover it

 

***Edit***

 

I have run it again without the body on, and it quieter again, so it must be the bodywork operating like a sound box, I have to think of someway to deaden the sound.

 

Regards,

 

Neil

 

 

 

 

Edited February 7, 2023 by neilkirby
Edit

[Barclay]

That looks amazing. Plastic spur gears don't create a lot of noise in my experience. If the body is acting as a sounding box then maybe something like blu-tac to damp vibration would work? Also regarding the lead shot - if it's not fixed in place it might be vibrating, but if you do fix it in don't use a water-based glue as the lead will oxidise/react over time and swell up, distorting the body potentially. Thoroughly coating the shot with epoxy is a safer bet and may also help with damping the sound.

[neilkirby]

Thank you, I was thinking about epoxy, and whether it generates any heat while curing. I left the shot loose for now as this was only a test print of the body. It turns out that I have a colleague whos son is a sound engineer. So I will see if he can come up with anything. in the mean time I will try a slight mod to the design and also try some silicone lubrication on the gears and try again.

Regards,

Neil

[DCB]

Spur gears always tend to be noisy,  Honda had a good idea on the 1970s 175 twin primary drive with pair of spur gears side by side but half a tooth out, might be a bit difficult with such a small model.

  If you have gone to this much trouble 3 d printing the body I would suggest  casting some lead weights by melting lead, shot, pipes, flashing, etc  and pouring into wooden moulds.  That way you can have weights shaped to fit tightly enough not to need glue.   That was always the cure for Hornby Panniers which loved to reverberate after they decided to fix the bodies with a screw through the side.  The Jnties etc with a central screw down the chimney were quiet  I don't know what adhesives attack your 3D plastic but I have melted an Airfix Dean Goods body with Uhu  trying to weight it with lead strips.

Edited February 9, 2023 by DCB