This winter's project. A transmission for the 302 engine

[gbritnell]

Yes sir you will.
George

 

[Lakc]

Good news indeed, thanks for sharing with us.

 

[gbritnell]

A little bit of a dry spell on the trans due to other modeling obligations. I got about 3 days on it over the past week and started on the gears. First up is the top cover. The last picture installment showed it machined but in need of finishing. I took care of that. While benching it out I saw an odd looking mark starting to form on the front bulkhead. I turned the cover over and discovered that I had machined the inside shape too close to the outside shape and as I was benching it out it started to break through. What to do? I set the part up on it's fixture plate and using a .09 slitting saw I cut through the front bulkhead down just deep enough to seat a patch into the front of the cover. I then turned up a disc the same diameter as the cutter and cut a piece off. With careful fitting I got an almost invisible seam. It just shows along the top. The next issue was how to secure the patch. I have tried many products over the years, CA glue, epoxies and what-have-you. Each one is good for it's own application but I have never had much luck adhering metal parts together, permanently. I had just been reading about JB Weld and having never used it I thought I would give it a try. I'm here to tell you that this stuff is amazing! It's also a 2 part epoxy type material but it has totally different characteristics than the usual 2 part epoxies. I used that to secure the patch from the inside. In the first picture you can see a faint line across the top where the patch butts up against the top cover surface. I couldn't peen that area prior to benching the patch out so the line will have to stay. The other surrounding areas of the patch fit up almost perfectly and there is no visible seam.
George

 

[gbritnell]

With the top cover and input shaft housing finished that takes care of all the aluminum housings. Now it's on to shafts and gears.
The first shaft was the input shaft. I had to make a spline cutter for the clutch end of it so first up was making a drill rod cutter for that. I had already made the gear cutters back when I had started the project. The shaft was turned and splined, the bearing was pressed into the cover. the input gear and shifter spline were machined and everything was pressed together with Loctite.
The splines on the end of the output shaft are different than the input shaft so a cutter was needed for that also.
George

 

[kustomkb]

Looking good George!

Sorry about the mishap. JB Weld has helped me out plenty of times. It can be drilled and tapped fairly well too.

 

[b.lindsey]

Got to agree, JB Weld is the Duct Tape of the 21st century. Its saved my rear on several occasions!! The project is still looking phenominal George, always look forward to your posts on it.

Bill

 

[gbritnell]

Here is a picture of the gear cutters I made for this project. In the past I have used store-bought involute cutters and home made flycutting bits. I had never tried making hob type cutters so I thought I would give it a shot. As has been covered on this forum, hob type cuttes work well for the fact that as the part is rotated to the next tooth the cutter will put the required radius onto the tooth. These were made from W-1 drill rod. When designing the trans gears I found that I would need three different pitches to give me the proper approximate gear ratios and still maintain the correct center spacing. I ended up with 36, 40 and 48 pitch gears. Close enough so that they don't look out of place in the trans but other than the 48's they are non standard sizes. When I made the first gear for the input shaft I cut enough stock to make an extra gear for test fitting. You can see the fit of teeth on the two gears is quite good for a homemade gear cutter. The hardest part in making the hobs is maintaining accurate spacing on the teeth. Each pitch needed it's own lathe tool bit to cut the hobs.
George

 

[gbritnell]

Here is the procedure for cutting teeth. This happens to be the countershaft. I needed to make it from 2 pieces as the inner gears were too close together to cut properly.
I chuck the stock in my set-true chuck and indicate it concentrically. I have my small surface gauge set to the centerline of the chuck and use it to center one of the teeth on the hob. When making the hob it's prudent to cut extra teeth. That way if it wears a little you can shift it up or down. The proper indexing plate is installed on the dividing head and then the cutting begins. For the 36 pitch gear the total depth is .06 so I take it all in one pass. The gears are being made from 12L14 so it cuts quite nicely.
George

 

[gbritnell]

Here are the 2 pieces of the countershaft. The large one has the input and 3rd gear gears and the smaller one has the second, reverse and first gear gears. After machining they were pressed and Loctited together.
George

 

[gbritnell]

The final set of pictures show the main case with the bearings installed, the mainshaft and input shafts in place and finally the countershaft sitting in the box.
I am so enthusiastic about working on the gears I would like to keep going but I have to finish up this current hit and miss engine first.
More to come!
George

 

[Ken I]

Nice going George.

As regards bonding metals the problem is that metals oxidise virtually instantly and no matter how good the glue is the bond is only as good as the "rust" and surface imperfections.

Specialist adhesives require primers for this purpose (hell if they can glue airplanes together why can't we ?)

A trick I use is to sand the mating surfaces using the epoxy as lubricant - this keeps the oxygen at bay and allows the adhesive to bond directly with the substrate. Do this to both surfaces - gently wipe clean - to remove the grit etc. but leave a film of adhesive - add a bit more clean adhesive and set up as per normal.

Generally gives a startling improvement in strength - up to 5 times better.

Regards,
Ken

 

[T70MkIII]

Stunning work, George - it's great seeing some internals going into the case. Thanks for the gearcutting pics; they've helped me get my head around the concept.

 

[ozzie46]

There are no words I can think of to express my admiration of this project adequately.

If I didn't know better I would think it was full size.

All I can say is GREAT JOB George! :bow: :bow: :bow: :bow: :bow:

Ron

 

[dsquire]

George

There is not much that I can say that hasn't already been said. A big thanks for letting me look over your shoulder again. :bow: :bow:

Cheers

Don

 

[Lakc]

Darn good stuff there George.
Do you climb mill with the hob or conventional mill them?
I have noticed that my homemade cutters do dull fairly easily, likely due to poor process control on my part. Looking forward to seeing it Saturday.

 

[gbritnell]

Hi Jeff,
I generally climb cut but on that last gear in the pictures I had to conventional cut it because I didn't feel safe with the runout room at the next gear.
George

 

[Chitownmachine]

One quick question...are you a robot, haha,...Because your work is beyond amazing!!! :bow: Out of curiosity what is your background in machining? I'm going to school for manufacturing engineering and electro-mechanical engineering so hopefully I can get a job as a prototype model maker. Your skills are super good and assumed you might be in the business . If you have any tips of any kind, as a fan of your work, I would love to hear em! Thanks again!!

 

[gbritnell]

Long story short, I served my apprenticeship with the Ford Motor Co. as a metal patternmaker. (4 years of school and on-the-job training) Worked in the field 38 years, part of that on the drafting board as a pattern designer. Learned CNC machines when they got them. The last 12 years worked as a CAD modeler and cutter path creator. (2 months of training throughout that time for program updates and related information) Now I just happily make chips in my basement shop.
George

 

[agmachado]

Hi George,

I don't have words for this... your project is reality very, very stunning !

But I need ask you... What is the material used to make the tool cut for the gears ?

Thank you for share this with us!

Cheers,

Alexandre

 

[gbritnell]

Thanks Alexandre,
I use W-1 drill rod. It is about the easiest to cut of the drill rods (silver steels).
I do the normal, heat to carrot orange, dunk straight down into water and swirl around. For tools like this that have a strong tooth section I don't draw them out. I only do that with tools that have small features. After hardening they are so brittle that a small shape will just snap right off. Once hard I go back with a diamond hone and clean up the cutting edges. These tools have no side relief on them but I have recut drill rod with them and they work fairly well.
George