Suspension Question

[stevendavis]

Working on my 2.5" gauge Green Arrow and have a question about setup. Do I need to set a sag, ( a gap between the axle blocks and stays), before I set the centerline for the feed pump location? Or do I set the axle centerline with the axle blocks resting on the stays?  And how strong should the springs be, light, medium, or hard pressure to move the blocks up? Thanks.

[millman]

The axleboxes should be set in their running position which I think for 2 1/2 gauge would be about 1/8 inch up from the horn keeps. There should be a centre line of motion drawn on your drawings to show the running height. Springs should be strong enough to hold axleboxes in their running positions, determined usually by good old trial and error.

[stevendavis]

Thanks millman!
Also, how far up and down do I chamfer the running surface of the axle blocks for tilt? And is careful hand filing the best way to accomplish this?

[millman]

Depends if you have one flange or two. If just one flange on the outside divide axleboxes height into three roughly equal parts and ease top and bottom thirds by a degree or so. If you have flanges inside and out, a slot, you will need to make the slot about .005” wider than hornblocks otherwise no matter how much the top and bottom are eased it will not rock. On 2.5 gauge I imagine if you can lift one side about 1/8” higher than the other you will be OK. I have tried machining the tapers, filing them and even CNC milling fancy curves, the best way is a nice sharp flat file with the files safe edge on the work. I was taught 60 years ago to always stone the safe edge of a new file to make sure it is “safe”, many have burrs on the edges and will damage the work. Hope this helps.

[stevendavis]

That helps a lot! Thank you!
Flanges are only on the outside of the horn blocks. I'll do 3rds and use a safe edge file for sure.

[stevendavis]

Have another question regarding lubricating the axles. What size drill should I use for the oil ports through the top of the axle box's? And what size countersink? I was thinking 1/4" on the countersink, and maybe a number 50 drill on the oil port hole?? Thanks.

[millman]

First off a question, are your springs above or below the axleboxes. If above I don’t suppose you have much space to spare, if below the top face of the axlebox is bare and you could drill a couple of 3/16 or 1/4 dia holes about 1/8 deep as oil reservoirs and drill your No50 hole down to the axle and also drill one sideways to lubricate the sides of the axlebox. Another method is to drill the end of the axle to a depth equal to where the middle of the axlebox will fall then cross drill the axle so oil goes down from the outside and out into the axlebox.

[stevendavis]

Thanks Millmam,
My springs are below the stays, so the top of the axle box's are bare. I didn't think of the horns. Sounds like I need to account for those as well??