20 degrees vs 14.5 degrees pressure angle for gears

If you did want to go the the expense of silver steel then 1m lengths are also a standard length just not from the usual ME suppliers, PGMS would be another option but a bit OTT

Like Andrew I went with bright bar though it took a couple of attempts to get a decent bit, first was bent and the second has quite a heavy spiral pattern down the outside more like you get on con cast bronze.

Thank you both for the replies.

Looks like college supplies at a show, and get a good bit, and at least see it before buying.

Hopefully, some new old stock that's straight.

I think this engine's a big step up from my previous model this may not be my last question.

Jason can probably vouch for that as you have helped me a lot in the past building the Minnie,

I owe you many pints.

steve.

I brought myself a 24" length of 1" precision ground EN1A from College Engineering Supply. I guess it is a little expensive, but on the other hand, in comparison to other parts it's not too much, and I knew it would fit well when the bearings were reamed. I didn't put bronze bushes into the hubs, so they are cast iron on the steel shaft, but I do have bronze bushes in the final drive tube, mostly because that was fairly easy to do with the castings I have from Bridport Foundry.

Hello all.

Another small question on my 3" drawings the hole on top of the smokebox tube says 7/8 but the chimney base castings bore says 1"-7/8 is the hole on the smokebox wrong. Attached photo of the drawing if i can manage to do it. Should they both be 1 -7/8"

Initially had trouble with the photo, finally found a way to post it the dimension I'm struggling with is the one marked in red, is this meant to be 1 - 7/8" not just 7/8" I know the drawing is to scale and it certainly bigger than 7/8" .

A question about your gears, did you use the cast blanks produced by Bridport for your 2nd motion gears?

Stephen, yes, I used the full set of castings from Bridport for the drive gear chain.

Hello again is there a reason the 2nd motion shaft fast gear has such a large boss. The drawing says 1-1/4" was wondering up the key caused problems and its been sized up from when my drawings were produced.

Any help greatly appreciated

Stephen, I'm not sure if this will help now as it's been best part of a month, but when I made the gears, I pretty much just followed the drawings. There's plenty of space for the large boss (you can just about make it out in the photos below).

The only thing I remember not being quite right on the drawings was that the dimension for the shoulder on the small gear didn't match up with the bore of the large gear, so I just ensured that they matched so that when the larger gear was bolted to the smaller one, it would fit on the shoulder and ensure that the gears are concentric.

Fusion 360 has an inbuilt script that allows gears to be modelled for direct CNC or 3D print.

See Kevin Kennedy's YouTube site on the link below. His site also has a lot of Fusion tutorial content.

**LINK**

Hello, just a final question in the gears with Keyways. Final pinion, slow gear etc.

What size would you use have you gone with the drawing say 3/16" x 5/32" but this doesn't sound like a square key?

Did you stick with imperial or swap to a metric size, and possibly square key cutting to half the key depth?

Any help I'm confused.. Stephen

Hello, hope you are well, can I ask the differential pinion gears, are these cast gears or have they been machined? I'm interested if they are also 10DP like the other gears as the drawings are not clear in the explanation. And also the 2 larger side gears bossed one and the no boss gear.

They look like cast gears.

If they were machined by the method in Ivan Law's book, they would be a different DP to similar scale spur gears.

There is a formula to work out which DP to use and which cutter number. It doesn't follow normal gear rules.

I have a spreadsheet that will do the maths and give the proper cutters and blank sizes.

Les

The bevel gears in the my traction engine from https://www.plastowtractionengines.co.uk/ are as-cast. I believe you can buy a fully machined set, but the cast gears work adequately well.

The main gear Pinion are machined cast iron blanks.

Edited By Martin Rock-Evans on 13/12/2022 16:00:48

These are the 3 gears that are part of the differential (OK, there are 2 pinions). They all have as-cast teath, and then the bosses/holes are machined as appropriate.

In motorcycle gearboxes and any other with trains of different size gears, the numbers of teeth in each pair add up to the same combined count. There is, however an allowance of one tooth which must be because the manufacturers can add or subtract a small ammount and still get good meshing at the same shaft centres.

i would make a TE axle from en 8 and then machine all over to obtain a better degree of straightness ,roundness and finish, I buy my steel in 3metre lengths from well known commercial suppliers and defects in the material can still occurr.why cut corners when building a model.

Thankyou all for the replies and great photo's.

Can I ask, do you know what cutter should be used for the large diff main gear Pinion's? I have the book and will do the maths, but so I can check I'm on the right lines with the workings out, before I commit to buying another cutter in error.

Thanks in advance.

(I've got the full set of 10DF cutters now lol - nice to have, and hardly used sharp ones).

Stephen.

Do you mean the bevel gear pinions?

Andrew

Hello, sorry yes the bevel gears. The 46 Teeth ones.