Gear info needed for Chuck's Hit Miss Engine

[deere_x475guy]

Thank you for your offer, and Yes I would like to have those! :bow: :bow: :bow: :bow:

I'll send you a PM.

-MB

Awh..good looks like gail is going to help you out.

 

[cfellows]

Sorry to get in on this late. Spent the whole day replacing a door frame and threshold. A lot harder than I thought it would be!

MB, the gears that Gail has generously offered will be perfect. I used 48 pitch gears on my engine, but they were 16 and 32 teeth respectively. They were actually a little too small in retrospect.

Chuck

 

[steamer]

At $25 a gear....make them!

Check out www.victornet.net

Victor Machinery

ABout $20 for a cutter.......


Dave

 

[Jasonb]

It looks like the ones I picked from small parts might also be too big. The 36 tooth is 1.125 pitch diameter and the small one is .562 inch.

any thoughts on those figures?

The PCD of the two gears must add up to twice the ctr to ctr distance of the two shafts so its not just a case of getting a 2:1 ratio.

For example a 10t & 20t would be a lot closer than a 20t & 40t but will still give the same ratio.

Jason

 

[Metal Butcher]

The PCD of the two gears must add up to the ctr to ctr distance of the two shafts so its not just a case of getting a 2:1 ratio.

For example a 10t & 20t would be a lot closer than a 20t & 40t but will still give the same ratio.

Jason

That's a very good point!

I need to have the gears in hand to determine the center to center distance.

This information is critical to make the gear side bearing block.

I'm thinking about making an eccentric bushing for the larger gear. This would allow for a little tweaking to compensate for wear and backlash.

Just a thought.

-MB

 

[mklotz]

I need to have the gears in hand to determine the center to center distance.

Well, not really. It's easy to work out...

The pitch diameter (PD) of a gear is given by:

PD = N/P

where:

N = number of teeth
P = diametral pitch = (N+2)/OD
OD = outside diameter

The CtoC distance (CD) is the average of the pitch diameters of the two gears.

CD = (PD1 + PD2)/2

Since P must be the same for both gears if they are to mesh (i.e., P1 = P2 = P), we have:

CD = (N1 + N2)/(2*P)

 

[Metal Butcher]

Sorry to get in on this late. Spent the whole day replacing a door frame and threshold. A lot harder than I thought it would be!

MB, the gears that Gail has generously offered will be perfect. I used 48 pitch gears on my engine, but they were 16 and 32 teeth respectively. They were actually a little too small in retrospect.

Chuck

Chuck, there's no need to apologize! I'd bet that door is dead on square! :big:

Yes! Gail's offer is very generous and unexpected. Thanks again Gail! :bow:

Chuck, can you provide the build information on the cam? Such as it's angles, diameter, lift, duration of lift. etc? Also, I can't find the drawing of the mechanism between the cam and valve in the head. It seems to be missing from the file repository in uploads.

Would it be possible to attach the cam to the side of the gear ( if that's not already how it's done) with 2 screws? This would allow and facilitate experimenting with different cam profiles.

Thanks.

-MB

 

[Jasonb]

So long as you know what gears you are going to use and their PCDs then you can make a start as said above.

However to get a nice meshing of the gears its handy to have them. slip a thin strip of fag paper between the teeth and push them into mesh, this will giove a slight clearance, you can then use a transfer punch to get the center distance or if you intend to do a lot make a gear depthing tool.

Jason

 

[Metal Butcher]

Well, not really. It's easy to work out...

The pitch diameter (PD) of a gear is given by:

PD = N/P

where:

N = number of teeth
P = diametral pitch = (N+2)/OD
OD = outside diameter

The CtoC distance (CD) is the average of the pitch diameters of the two gears.

CD = (PD1 + PD2)/2

Since P must be the same for both gears if they are to mesh (i.e., P1 = P2 = P), we have:

CD = (N1 + N2)/(2*P)

Thanks Marv, I appreciate you effort, and I'm sure that information is the proper way to determine ctc gear hole locations. And I"m sure that there are members on this forum that understand the formula and can use it.

Unfortunately I don't have the math skills to use your mathematical formulas.

I do have a good feel for fits, and can quickly drill 2 holes at a measured distance in a scrap block to test my method of measurement and make any necessary adjustment.

My brother in-law is always intrigued with the engines I build and my basic common sense approach to solving problems. I enjoy the many long and technical conversations we have on a variety of subjects that manage to keep my wandering mind focused . He is well educated and has a PHD in Nuclear Physics, go figure!

Since this is a hobby for me just "winging it" can be a lot of fun! ;D

-MB

 

[mklotz]

All the math is already implemented in the GEAR program on my page. All you need to do is enter the number of teeth on your two gears and it will compute, among a number of things, the center-to-center spacing.

 

[Metal Butcher]

All the math is already implemented in the GEAR program on my page. All you need to do is enter the number of teeth on your two gears and it will compute, among a number of things, the center-to-center spacing.

Thanks again Marv. When I have the gears I'll give it a try.

My wandering mind raises a new question.

Are the gears I'll be using within the specifications used as the basis for the formula to calculate their exact location?

Hmm....

-MB



.

 

[mklotz]

Are the gears I'll be using within the specifications used as the basis for the formula to calculate their exact location?

The formulae are valid for any spur gears - the most common type of gear.

 

[GailInNM]

MB,
The gears are in the mail, first class in a padded envelope.

The theoretical C-C distance would be 0.625 for them. I looked at my drawing and see that I made it 0.627 on mine. There is a small amount of backlash, but not enough to hurt anything. These gears are so lightly loaded that about anything would be acceptable.

The 40 tooth gear is a surplus MIL spec gear so it should be good. The 20 tooth is one I made so it may not be to spec, but it will be close.

You can adjust the cam to deliver different kinds of performance depending on what you want. I tried a couple of different things. What I ended up with is a fast rise with very little dwell angle. I can run a little bit higher pressure that way and that gives a better sounding bark while still giving good low speed performance. No good for power, but I did not intend to load it with anything.

I can post a jpg of either the drawing or photo if you want it, but it's probably more fun to just play. I put a 1/4 inch OD ball bearing in for the cam follower to keep friction down with the fast rise.

Have fun,
Gail in NM,USA

 

[cfellows]

Chuck, can you provide the build information on the cam? Such as it's angles, diameter, lift, duration of lift. etc? Also, I can't find the drawing of the mechanism between the cam and valve in the head. It seems to be missing from the file repository in uploads.

Would it be possible to attach the cam to the side of the gear ( if that's not already how it's done) with 2 screws? This would allow and facilitate experimenting with different cam profiles.

Thanks.
-MB

MB, the valve lift needs to be 1/16" or so and you don't need much clearance between the valve and the push rod. You want the valve to open quickly at or a little after TDC, and you want it to close well before BDC, as much as 45 degrees.

On my engine, I made the cam with a hub and mounted the gear over the hub. A single screw through the cam lobe into the gear holds it all together. The attached picture may help some.

 

[Metal Butcher]

Thanks Gail. :bow:

I wrote down those figures since it will be awhile before I can get to that part of the build. No need to post a picture I have enough of your cam information to go by.


Thanks Chuck. :bow:

Your photo and description also tells me what I needed to know about the cam shape and mounting method.

I,m getting real close to having enough info to start building.

All that's needed is more bad weather ( its snowed today!) and some details on the cam follower.


-MB