help on alchin drawings

Hi i am Joe

starting tobuild Alchin but the cost of the castings and such are really expensive forme.

I have access to a good machine shop and machine ools.

Wantto make the sets of gears and have the 16 pd set of cutters. From the engineers data formulea forgears the OD and depth of cut can be calculated from Gear OD divided by PDbuton the 6 inchodd gear the depth of cut seems very large some nearlly 3/8.

is this correct.

regards Joe

Depth of cut is Addendum + Dedendum

So for 16DP the addendum is 1/16 and dedendum 1.25/16 = 2.25/16 = 0.141"

Diameter has no relation to depth of cut.

Jason is correct, tooth depth has no relation to the number of teeth and hence OD.

The OD of a gear is the tooth count (N) plus 2 all divided by the diametric pitch (P):

OD = (N + 2)/P

For diametric pitch gears the addendum (J) is the inverse of the DP:

J = 1/P

In theory the dedendum is equal to the addendum, but in practice some clearance is needed, so the dedendum is greater than the addendum. The clearance is arbitrary but the dedendum is normally 1.157 divided by the diametric pitch:

K = 1.157/P

For smaller tooth count gears the clearance can be increased so the dedendum becomes:

K = 1.25/P

The total depth of cut should be marked on the involute cutters, often defined as Df, or D+F. For the cases above it will be 2.157 or 2.25 divided by P.

Andrew

dear both

that is really helpful and thanks so much for taking the time to reply.

I have the book but some information is not there, does any one have the dimensions of front wheel hub. Its not articulated in the drawings

best regards

joe

The front hubs are all there in the book, hidden away along the bottom of the side view with painting details, page 246 of the book.

The drawings in the book are just reduced size ones you can buy.

Jason

thanks somuch for that i appreciate it.

Like the full scale drawings but seen themand allaresoexpensive now.

regards

Joe

me again.

Regarding the gears i just checked and the cutters are there allexcept the ones to cut the 22,20 and 26.

Could i get away with using the 16 tooth one or the 30?

I dohave a 1.75mod set would it better to replace with that?

thanks in advance

joe

Assuming the engine design is imperial I wouldn't change to Mod gears. 1.75 Mod is not exactly the same as 16DP. The Mod gears will have different centre to centre differences, even if the tooth counts are tweaked. Before you know it the change will turn into a major redesign exercise.

Using the incorrect gear cutter will result in the wrong curvature on the teeth, so the gears will not mesh smoothly. If the incorrect cutter is to be used better to use one with a lower tooth count than the gear, as the tooth will end up more curved than they need to be. They will mesh with another gear. if the tooth is less curved than it needs to be it may not mesh at all.

Andrew

Andrew

Thanks for the advice certainly give that a go.

Joe