Author Topic: Question for the hit & miss crowd  (Read 1072 times)

Offline stevehuckss396

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Question for the hit & miss crowd
« on: December 02, 2018, 10:57:25 PM »
I have never built a H&M engine so I was wondering what the popular spark plug sizes are. Having purchased Dale Detrich's stock of plugs and parts last year it's time for me to get going on the endevor. I have 1/4-32 and 8-40 plugs that dale designed as well as my own 8-40 design from the Demon project. I also plan to make my own 1/4-32 and 10-40 plugs for sale. For the hit and miss crowd I was tossing around the idea of making copies of the X3 plugs in 1/4-32. I have done some reading and it appears that that was a popular plug in the full scale H&M engines way back when. With there being so many different engines and sizes i would like some help on where to start.

Would the X3 be a good choice or is there a different plug that would be more appropriate for a H&M engine?
Of the models out there would 1/4-32 be a good place to start or is 10-40 more popular a thread size on the H&M's

Any information or suggestions for future designs are very much welcome.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline gbritnell

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Re: Question for the hit & miss crowd
« Reply #1 on: December 03, 2018, 01:50:35 AM »
Hi Steve,
I have made plugs in all sizes but I would have to say that 1/4-32 is probably the standard for most engines. On some of the larger engines I have built they use a CM-6 which is a M10 x 1.0 metric size. At one time there were some 3/8-24 plugs around but I don't think anyone uses them.
When I'm building an engine I size the plug to the size of the engine so it looks proportional. Not very scientific but they look good.
gbritnell
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Online Jasonb

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Re: Question for the hit & miss crowd
« Reply #2 on: December 03, 2018, 03:25:09 PM »
All the ones that I have made have taken a CM-6 plug so M10x1 thread. I think a 1/4" thread may look too small on anything over a 1" bore but would depend on the scale of the engine as mine have been 1/2 or 1/3 scale so 1.5" + bore.

If you are thinking of making them as substitutes for CM-6 then make sure the threaded part is long enough as a CM6 is about twice the length of a standard 1/4" Rimfire.

Maybe 5/16 or M8 x 1 would be a good compromise in size.

Not sure what your plugs will sell for but you can now get far Eastern 1/4" plugs for a lot less than Rimfire so our members with tight purse strings may not want to pay more than that.

Can you post a link to a X3 plug as google just wants to sell my ones for a BMW X3

Offline stevehuckss396

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Re: Question for the hit & miss crowd
« Reply #3 on: December 03, 2018, 08:07:55 PM »
Thanks George!

For reference a 1/4-32 is real close to 1/3rd scale

I'm not sure what a chinese 1/4-32 costs but i am thinking I can do them for around 10 bucks each and the 8-40 for about 15 bucks.  The X3 i am shooting for $20.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline steamer

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Re: Question for the hit & miss crowd
« Reply #4 on: December 03, 2018, 11:23:17 PM »
Thanks George!

For reference a 1/4-32 is real close to 1/3rd scale

I'm not sure what a chinese 1/4-32 costs but i am thinking I can do them for around 10 bucks each and the 8-40 for about 15 bucks.  The X3 i am shooting for $20.

Don't care what the Chinese charge for them....Im buying them from you Steve.     8)

Dave
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Offline stevehuckss396

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Re: Question for the hit & miss crowd
« Reply #5 on: December 04, 2018, 12:20:30 AM »
Thanks George!

For reference a 1/4-32 is real close to 1/3rd scale

I'm not sure what a chinese 1/4-32 costs but i am thinking I can do them for around 10 bucks each and the 8-40 for about 15 bucks.  The X3 i am shooting for $20.

Don't care what the Chinese charge for them....Im buying them from you Steve.     8)

Dave


Thanks bud!  At least I know I have one sold.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline steamer

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Re: Question for the hit & miss crowd
« Reply #6 on: December 04, 2018, 12:43:11 AM »
I got more faith than that my friend.   Listen...Us guys spend endless hours making engines that only a select group are impressed with...why put a crap spark plug in it?

Just sayin.... 8)

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline stevehuckss396

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Re: Question for the hit & miss crowd
« Reply #7 on: December 04, 2018, 01:04:06 AM »

Not sure what your plugs will sell for but you can now get far Eastern 1/4" plugs for a lot less than Rimfire so our members with tight purse strings may not want to pay more than that.


The 1/4-32 plugs are anywhere from 12 - 18 bucks depending on where you look. If I can do 10 bucks I will be OK. The CM-6 i cant touch. Seen them for under 5 bucks
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Offline 10KPete

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Re: Question for the hit & miss crowd
« Reply #8 on: December 04, 2018, 01:31:07 AM »
I got more faith than that my friend.   Listen...Us guys spend endless hours making engines that only a select group are impressed with...why put a crap spark plug in it?

Just sayin.... 8)

Dave

I'm with you there, Dave!  It's good to know that these plugs will continue to be made by a fellow ME...

Pete
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Offline 10KPete

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Re: Question for the hit & miss crowd
« Reply #9 on: December 04, 2018, 01:32:20 AM »
Steve, remember that it's not important to make 'em cheaper. Make 'em better!!

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline steamer

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Re: Question for the hit & miss crowd
« Reply #10 on: December 04, 2018, 01:48:01 AM »
Steve, remember that it's not important to make 'em cheaper. Make 'em better!!

Pete


Wot Pete Said!!!!!
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline stevehuckss396

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Re: Question for the hit & miss crowd
« Reply #11 on: December 04, 2018, 01:59:19 AM »
Steve, remember that it's not important to make 'em cheaper. Make 'em better!!

Pete

Yes sir they will be deluxe or i'm not going to sell them. Same basic construction as Dales plugs and they have been in my Peewee for 8 years.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Online Jasonb

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Re: Question for the hit & miss crowd
« Reply #12 on: December 04, 2018, 07:16:28 AM »
So does not sound like Jo will be buying from you then.

If 1/4 is about right for a one third scale that makes them around 3/4 the ad so the CM6 or a 3/8 would be right on half scale. Though the hex is a bit oversize so a scale body would still look better and if you could also do the screw top that would be a nice touch.

Offline stevehuckss396

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Re: Question for the hit & miss crowd
« Reply #13 on: December 12, 2018, 01:04:57 AM »
So I modeled up the Champion Com6 in 1/4 scale. I believe this was a popular plug back in the day. The threads are not arranged like the original plug. I put a more standard 10-40 thread. The cap is not to scale. I had to increase it so that the smallest plug wire clip would fit on it. The biggest problem is in 1/4 scale the body and cap are only about 1/4 inch away from each other. Could be some arching across the insulator. Once I get some 8-40 and 10-40 in stock I'll build a few and see if i can find someone to test them.

 
Do not be like the cat who wanted a fish but was afraid to get his paws wet.