Perhaps worst case, if a tooth breaks off, leave it off, and cut that tooth after casting?
Looking good.
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Looking good.
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Gears
- Thread starter sawyer massey
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I admire what you are doing, you will end up with workable gears I am sure.
It is always easy to comment on others work when you don’t know what facilities they have, but why not cast a blank and mill the teeth? I have completed a traction engine gear for a friend, this was 20” diameter in cast iron. We attached the blank to a rotary table and milled the teeth with a horizontal set up. We fed the blank vertically. A disc of MDF between the blank and table along with a clamp before each cut and going round twice worked OK.
The compensating gear teeth were used as cast and by careful filing and running in they worked well.
I have made compensating gears for a smaller engine from the eye were about 6” diameter and again milled horizontally.
Great work, keep going and posting, thanks
It is always easy to comment on others work when you don’t know what facilities they have, but why not cast a blank and mill the teeth? I have completed a traction engine gear for a friend, this was 20” diameter in cast iron. We attached the blank to a rotary table and milled the teeth with a horizontal set up. We fed the blank vertically. A disc of MDF between the blank and table along with a clamp before each cut and going round twice worked OK.
The compensating gear teeth were used as cast and by careful filing and running in they worked well.
I have made compensating gears for a smaller engine from the eye were about 6” diameter and again milled horizontally.
Great work, keep going and posting, thanks
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The casting has protrusions on it and won't clear a 4 DP diameter cutter .....or a hob ....thanks I did the gears for my 1/4 Sawyer Massey that way on a horizontal mill
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Richard Hed
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how about using a shaper, grind yo9ur tool to the shape of the tooth and cut away
Cast iron gears were used for many years in the water and steam driven mills of the early industrial revolution.
Lubrication was by tallow and water. Every year the mills would close for 2 weeks and teams of men would inspect the gears and take off the shiny high spots with chisels. Payment for this work , apparently , was the old tallow from the bearing boxes , which they would clean and sell to the next mill.
I don't think we give much thought to the development of machine tools , we have difficulty sometimes with hard spots in iron castings but imagine making the bore down a 32 pounder iron cannon.....no TC or HSS tooling then.
How were screw threads made ? in Birmingham (UK) science museum is a lathe leadscrew , if I remember correctly it is about an inch and a half diameter and five or six feet long , it was filed from a steel bar by hand and was then used on a lathe to screwcut a second.
The mind boggles !
Dan.
Lubrication was by tallow and water. Every year the mills would close for 2 weeks and teams of men would inspect the gears and take off the shiny high spots with chisels. Payment for this work , apparently , was the old tallow from the bearing boxes , which they would clean and sell to the next mill.
I don't think we give much thought to the development of machine tools , we have difficulty sometimes with hard spots in iron castings but imagine making the bore down a 32 pounder iron cannon.....no TC or HSS tooling then.
How were screw threads made ? in Birmingham (UK) science museum is a lathe leadscrew , if I remember correctly it is about an inch and a half diameter and five or six feet long , it was filed from a steel bar by hand and was then used on a lathe to screwcut a second.
The mind boggles !
Dan.
I worked on casting a pair of gears for a windmill restoration a few years ago, and got close to succeeding, before I got too busy with work projects to continue.
I often heard the question "Why not just cast a blank and then machine it?".
The answer is that gears, complete with teeth, have been cast in foundries for a very long time, and so there is no reason we cannot recapture this technology.
Another answer is that if you don't have the appropriate gear cutters, machines, indexing heads, and knowledge, you cannot cut accurate gears into a blank. 3D printed gear patterns don't require any equipment other than a computer and some software.
And a third answer is that when building model engines, if one can cast gears, then one does not need to conform to some standard gear cutter form/size.
Gears can be 3D printed at any size, and then cast.
An example are the gears below that were modeled in 3D by JasonB.
These will be cast in gray iron, and will be used for a Frisco Standard IC marine engine, and the intent is that once cast, they will be accurate enought to work with just a light cleanup of the surfaces. With resin-bound sand, I think this is entirely possible.
When you are a machinist, everything looks like a block of metal to be machined into some final shape.
When you do foundry work, everything looks like a pattern, and the idea is to cast a part that is very close to final shape, so that most or even all of the post-casting machining work is eliminated.
Different approaches for folks with different skill, and equipment sets (and different mindsets).
It is like the question "Why climb Everest? Why not just hike around it?".
And the answer is that if you can climb Everest, then chances are you can do a lot of other things that you never dreamed you could do.
And the Everest-climbing skills can be applied to many other endeavors, which is akin to adding valuable tools into your tool kit.
I often heard the question "Why not just cast a blank and then machine it?".
The answer is that gears, complete with teeth, have been cast in foundries for a very long time, and so there is no reason we cannot recapture this technology.
Another answer is that if you don't have the appropriate gear cutters, machines, indexing heads, and knowledge, you cannot cut accurate gears into a blank. 3D printed gear patterns don't require any equipment other than a computer and some software.
And a third answer is that when building model engines, if one can cast gears, then one does not need to conform to some standard gear cutter form/size.
Gears can be 3D printed at any size, and then cast.
An example are the gears below that were modeled in 3D by JasonB.
These will be cast in gray iron, and will be used for a Frisco Standard IC marine engine, and the intent is that once cast, they will be accurate enought to work with just a light cleanup of the surfaces. With resin-bound sand, I think this is entirely possible.
When you are a machinist, everything looks like a block of metal to be machined into some final shape.
When you do foundry work, everything looks like a pattern, and the idea is to cast a part that is very close to final shape, so that most or even all of the post-casting machining work is eliminated.
Different approaches for folks with different skill, and equipment sets (and different mindsets).
It is like the question "Why climb Everest? Why not just hike around it?".
And the answer is that if you can climb Everest, then chances are you can do a lot of other things that you never dreamed you could do.
And the Everest-climbing skills can be applied to many other endeavors, which is akin to adding valuable tools into your tool kit.
GreenTwin, how would you compare resin-bound sand to CO2-cured sodium silicate sand? Would it be equally possible to create a mold in the latter?
I have used sodium silicate bound sand with aluminum, but not with iron.
I have had discussions with the local art-iron group, and they have used SS sand with iron, and report good results.
One thing I do with resin-bound molds is to flame them lightly with a wide propane flame, to drive off any residual resin or moisture.
A second thing I do with resin-bound molds is to spray them with a ceramic mold coat, which helps greatly with creating a smooth surface finish.
I have not tried spraying ceramic mold coat (alcohol-based) onto a SS mold, and don't know if it would dissolve the SS or not.
The resin molds have to be flamed first, the ceramic mold coat sprayed on, and the molds flamed again.
If I had a bit more time, I would go out to the shop and experiment with some SS molds, and mold coat.
I think one can get results similar to resin-bound sand, using sodium silicate bound molds; that is what I have heard.
And sodium silicate is readily available at pottery supply houses too, unlike resin for molds.
Sodium silicate molds can be cured with CO2, or a catalyst can be added that automatically cures SS molds.
It is important to keep the patterns well waxed with bound sand, since they tend to cling to the sand.
And if you leave your pattern in bound sand after the strip time, then your pattern is basically permanently glued into the mold (don't ask me how I discovered this).
PatJ
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I have had discussions with the local art-iron group, and they have used SS sand with iron, and report good results.
One thing I do with resin-bound molds is to flame them lightly with a wide propane flame, to drive off any residual resin or moisture.
A second thing I do with resin-bound molds is to spray them with a ceramic mold coat, which helps greatly with creating a smooth surface finish.
I have not tried spraying ceramic mold coat (alcohol-based) onto a SS mold, and don't know if it would dissolve the SS or not.
The resin molds have to be flamed first, the ceramic mold coat sprayed on, and the molds flamed again.
If I had a bit more time, I would go out to the shop and experiment with some SS molds, and mold coat.
I think one can get results similar to resin-bound sand, using sodium silicate bound molds; that is what I have heard.
And sodium silicate is readily available at pottery supply houses too, unlike resin for molds.
Sodium silicate molds can be cured with CO2, or a catalyst can be added that automatically cures SS molds.
It is important to keep the patterns well waxed with bound sand, since they tend to cling to the sand.
And if you leave your pattern in bound sand after the strip time, then your pattern is basically permanently glued into the mold (don't ask me how I discovered this).
PatJ
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Thanks, Pat, very helpful information as always. I am still working on my furnace, but hope to be trying my hand at some aluminum casting before too long. Down the road I would love to try iron, and I am building the furnace with that in mind. I have picked up some supplies from time to time in anticipation, and thus I have a gallon of SS on hand - and thus the question!
I had not heard about a catalyst that could be added to SS sand. That sounds very interesting indeed, as I can easily imagine situations where getting the CO2 to the right places could be difficult. I would love to learn more about this ... which is my attempt to find a round about way to say, "please tell me more but only if I am not causing too much trouble."
I had not heard about a catalyst that could be added to SS sand. That sounds very interesting indeed, as I can easily imagine situations where getting the CO2 to the right places could be difficult. I would love to learn more about this ... which is my attempt to find a round about way to say, "please tell me more but only if I am not causing too much trouble."
Well, we are hijacking Sawyer Massey's gear casting thread big time, so we better move the sodium silicate conversation elsewhere.
I will look for that casting thread I started, and post a link.
Edit:
Here is the link to the foundry thread I started.
We can discuss more here.
https://www.homemodelenginemachinist.com/threads/home-foundry.33291/page-12
I am still anxiously awaiting the outcome of Sawyer Massey's gear casting attempt.
Any news on that?
.
I will look for that casting thread I started, and post a link.
Edit:
Here is the link to the foundry thread I started.
We can discuss more here.
https://www.homemodelenginemachinist.com/threads/home-foundry.33291/page-12
I am still anxiously awaiting the outcome of Sawyer Massey's gear casting attempt.
Any news on that?
.
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Hopefully Sunday......if it's above freezing ......or at least close to it ......cold in Ontario and the foundry gets moved out side
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3 wrongs don't make a right
1 short of iron .......hard that should of had 3 lb extra ..not
2 plywood weighted down right on the box ... So couldn't vent through the sand
3 did not use horn sprue
Well there goes that weekend .......learn for my mistakes I will I hope lol
Thanks
Todd
1 short of iron .......hard that should of had 3 lb extra ..not
2 plywood weighted down right on the box ... So couldn't vent through the sand
3 did not use horn sprue
Well there goes that weekend .......learn for my mistakes I will I hope lol
Thanks
Todd
Attachments
That is not a bad attempt, and oh so close to being usable.
I have not successfully cast a gear yet, and the gear I was trying to cast was solid, and did not have spokes.
I have not used a horn sprue (I don't think I have used, not intentionally anyway).
I have seen several schools of thought on how to cast spoked flywheels.
One thought is to use the rim of the flywheel as the runner.
I am not a fan of this method because if you get trash in the runner, it gets imbedded in the casting.
A second school of thought, and the method I generally try to use, is to have one or more separate runners, with spin-traps at the end of each runner. Sometimes this requires a larger crucible, and so I seldom see others use it.
For this gear, I would have two runners, arranged like a horseshoe.
Spin trap on the end of each runner, sprue at the center of the horseshoe.
I would have four long gates, two on each runner, which could connect to the bottom of the gear rim.
The runners would be in the drag along with the gates, and the gear pattern would all be in the cope.
I would use a 1 1/2" diameter riser in the center at the hub.
The intent would be to entirely fill the runners, and let the excess start to flow into the spin traps, before the level got high enough to fill the gates.
The gates would be long, sort of like knife gates.
Since you will machine the face of the rim, you will trim off the gates during machining.
There are lots of thin teeth to fill, and so the idea is to use generous runner sizes, perhaps twice the section of the rim, and generous gates. The metal would fill the runners first, and the cool front wave would go up the spin traps, along with the slag and lose sand. The fresh hot metal in the runners would then start flowing in the gates, and with large gates, could fill the mold quickly.
I make the bottom of the sprue so that it smoothly transitions into both runners, to minimize turbulence.
The sprue would also be generously sized, but not so large that it would not stay completely full during the pour.
I guess the gates would ultimately regulate the flow if sized correctly, so an oversized sprue could be used as long as it was kept full.
If you still had too much shrinkage in the teeth, you may have to add about four small risers around the rim.
It is a rather tricky part to cast, but gears were very commonly cast back in the day, so it is just a matter of figuring out what works.
That is my slant on how I would approach it.
Edit:
Those tabs sticking off of the gear make things a bit tricky.
.
I have not successfully cast a gear yet, and the gear I was trying to cast was solid, and did not have spokes.
I have not used a horn sprue (I don't think I have used, not intentionally anyway).
I have seen several schools of thought on how to cast spoked flywheels.
One thought is to use the rim of the flywheel as the runner.
I am not a fan of this method because if you get trash in the runner, it gets imbedded in the casting.
A second school of thought, and the method I generally try to use, is to have one or more separate runners, with spin-traps at the end of each runner. Sometimes this requires a larger crucible, and so I seldom see others use it.
For this gear, I would have two runners, arranged like a horseshoe.
Spin trap on the end of each runner, sprue at the center of the horseshoe.
I would have four long gates, two on each runner, which could connect to the bottom of the gear rim.
The runners would be in the drag along with the gates, and the gear pattern would all be in the cope.
I would use a 1 1/2" diameter riser in the center at the hub.
The intent would be to entirely fill the runners, and let the excess start to flow into the spin traps, before the level got high enough to fill the gates.
The gates would be long, sort of like knife gates.
Since you will machine the face of the rim, you will trim off the gates during machining.
There are lots of thin teeth to fill, and so the idea is to use generous runner sizes, perhaps twice the section of the rim, and generous gates. The metal would fill the runners first, and the cool front wave would go up the spin traps, along with the slag and lose sand. The fresh hot metal in the runners would then start flowing in the gates, and with large gates, could fill the mold quickly.
I make the bottom of the sprue so that it smoothly transitions into both runners, to minimize turbulence.
The sprue would also be generously sized, but not so large that it would not stay completely full during the pour.
I guess the gates would ultimately regulate the flow if sized correctly, so an oversized sprue could be used as long as it was kept full.
If you still had too much shrinkage in the teeth, you may have to add about four small risers around the rim.
It is a rather tricky part to cast, but gears were very commonly cast back in the day, so it is just a matter of figuring out what works.
That is my slant on how I would approach it.
Edit:
Those tabs sticking off of the gear make things a bit tricky.
.
Last edited:
ajoeiam
Well-Known Member
well - - - a bloody pile of work all to try it over again!!! bummer that!
I like what you've done - - - - a lot!!!
Appreciate the sharing - - - - if I get to trying casting - - - hopefully I can learn from what you're showing!
(Likely I will have to make my own mistakes - - - LOL.)
Richard Carlstedt
Well-Known Member
Green Twin is right on and I have one small comment.
Years ago I was casting a 16 inch flywheel and failed several times, until a foundry old timer
told me to never do what I was doing- I was adding vents and risers without success.
He said to " never pour rings flat" , always cock the mold a bit so the air knows which way to escape
On the next pour I place a 3/4" board under one end of the mold and got " Perfect" results
Rich
Years ago I was casting a 16 inch flywheel and failed several times, until a foundry old timer
told me to never do what I was doing- I was adding vents and risers without success.
He said to " never pour rings flat" , always cock the mold a bit so the air knows which way to escape
On the next pour I place a 3/4" board under one end of the mold and got " Perfect" results
Rich
There has been some debate about venting molds, and some demonstrations of how some not vent molds and still get good castings (using green sand that is permeable).
I definitely have to vent the high points of my resin-bound molds because I have ruined castings when large air bubbles get trapped at the top of the molds.
I drill an 1/8" (can be slightly smaller) hole at the high points in the cope mold, and this allows the air to escape.
My thoughts are that when in doubt, use vents at the high points of the mold.
Vents cost nothing, and are sort of an insurance policy, ie: you may not need them, but better to have them and not need them, then to need them and not have them.
I have not tilted any molds, but have heard of others doing that with good success.
I would guess that tilting the mold slightly allows a progressive fill up/across the mold cavity.
Since I have not had problems with no tilting, I would guess it may be more related to the size/type/layout of the pattern, and also related to the layout of the runners, gates, etc.
The sprue/gates/runners/risers design is a bit of an art, and everyone has their favorite method.
Bottom line is that the design has to work consistently and not entrain air, sand, or slag into the mold cavity.
Rule number one (in my book anyway) is to control the metal velocity at all times.
Molten metal splashing into the mold cavity will cause all sorts of defects.
The molten metal flow needs to be laminar, and should fill the mold as fast as possible without causing turbulence, and without eroding the sand mold (erosion applies to green sand molds, not resin-bound molds).
There are some mold fill simulation videos out there, and they show what happens when the velocity is too high, and the metal splashes inside the mold cavity, with the resultant casting defects.
.
I definitely have to vent the high points of my resin-bound molds because I have ruined castings when large air bubbles get trapped at the top of the molds.
I drill an 1/8" (can be slightly smaller) hole at the high points in the cope mold, and this allows the air to escape.
My thoughts are that when in doubt, use vents at the high points of the mold.
Vents cost nothing, and are sort of an insurance policy, ie: you may not need them, but better to have them and not need them, then to need them and not have them.
I have not tilted any molds, but have heard of others doing that with good success.
I would guess that tilting the mold slightly allows a progressive fill up/across the mold cavity.
Since I have not had problems with no tilting, I would guess it may be more related to the size/type/layout of the pattern, and also related to the layout of the runners, gates, etc.
The sprue/gates/runners/risers design is a bit of an art, and everyone has their favorite method.
Bottom line is that the design has to work consistently and not entrain air, sand, or slag into the mold cavity.
Rule number one (in my book anyway) is to control the metal velocity at all times.
Molten metal splashing into the mold cavity will cause all sorts of defects.
The molten metal flow needs to be laminar, and should fill the mold as fast as possible without causing turbulence, and without eroding the sand mold (erosion applies to green sand molds, not resin-bound molds).
There are some mold fill simulation videos out there, and they show what happens when the velocity is too high, and the metal splashes inside the mold cavity, with the resultant casting defects.
.
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I use green sand ,the only time I use vents now is on cores ....the core in the engine frame is bigger than the casting lol
I found when I used vents I got shirink under then and in some cases blow holes ...
That was the first time I put the plywood right on the face of the sand ...I usually put barbecue grates under the plywood to hold the sand and still vent it
But the next on I pour will be horn gated which the top of the horn is a vent and a feeder .....best I understand
We will try again Sunday ........ with better results I hope lol
Thanks for you help
Oh and all the gear is in the middle box
The top box has the feet .....has I cut the feet out telcum powdert the cut out and pack the top box .....so that area hangs down from the face
I do the same for the inside of the gear on the bottom box ....it is blanked off when I pack the gear so all it is is a disk 1/2.. inch thick and acts like a core....can take pictures next time I pack if you like
Thanks
Todd
I found when I used vents I got shirink under then and in some cases blow holes ...
That was the first time I put the plywood right on the face of the sand ...I usually put barbecue grates under the plywood to hold the sand and still vent it
But the next on I pour will be horn gated which the top of the horn is a vent and a feeder .....best I understand
We will try again Sunday ........ with better results I hope lol
Thanks for you help
Oh and all the gear is in the middle box
The top box has the feet .....has I cut the feet out telcum powdert the cut out and pack the top box .....so that area hangs down from the face
I do the same for the inside of the gear on the bottom box ....it is blanked off when I pack the gear so all it is is a disk 1/2.. inch thick and acts like a core....can take pictures next time I pack if you like
Thanks
Todd
Sounds like you are using a cheek.
Cheek
Intermediate sections of a flask inserted between cope and drag.
Necessitated by difficulty in molding unusual shapes, or in cases where more than one parting line is required.
From foundry definitions located here:
http://www.atlasfdry.com/glossaryc.htm
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Cheek
Intermediate sections of a flask inserted between cope and drag.
Necessitated by difficulty in molding unusual shapes, or in cases where more than one parting line is required.
From foundry definitions located here:
http://www.atlasfdry.com/glossaryc.htm
.
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