Mintor 22 Piston
 

This is no way a bad report of the Mintor line of engine's so let's not turn it into one please.

A friend of mine contacted me about his Mintor 22 and a noise it was making . After he did a quick tear down it was discovered the piston had excess skirt clearance and he sent it to me to see about making a new piston for the engine.
I double checked his findings and found a whoppin .0065 clearance a slightly out of round and tapered cylinder. That make things a little on the harder side to get a perfect piston fit.
Anyway after a material type and grade was made I was able to get started on the task at hand.
The original piston is machined from a billet piece of stock similar to what I have done here.
Now if I can download some pics I'll give ya all a peek at what I have been up to lately.http://www.rcuniverse.com/forum/atta...mentid=2040825http://www.rcuniverse.com/forum/atta...mentid=2040826http://www.rcuniverse.com/forum/atta...mentid=2040827http://www.rcuniverse.com/forum/atta...mentid=2040828http://www.rcuniverse.com/forum/atta...mentid=2040829http://www.rcuniverse.com/forum/atta...mentid=2040830

+1

Looking good

everyone needs a friend like you, or at lease I do,nice work.

Absolutely outstanding workmanship. What skirt clearance will the new piston have in the cylinder, also in the picture showing both pistons, which is the new one ??

I agree with Karolh, that is some of the best work I have seen done. Looks like that Mintor is going to run even better. It is great to see the workmanship we have here in the USA. I know there is, because I have gone to several forums & seen complete home made multi cylinder made engines of all types. There is also video on youtube of them running.
https://www.youtube.com/watch?v=qDnrfadNVfk https://www.youtube.com/watch?v=tl0nD1smbAg

https://www.youtube.com/watch?v=NrQ6fmUmMt4 Capt,n

With the cylinder having some taper the best I could fit the piston was .002-.0025 which should be fine as it gets smaller towards the top. I didn't want it to tight even with the high silicon alum there could be some growth.
We'll know for sure tomorrow when I fire it up.
The new piston is on the right side the one with the ring in it. Sorry the pic went a little blurry.

I know some one is going to ask what kind of aluminum was used, it is 4032 available at McMaster Carr.

Oh I forgot to add this, thank you all for the nice comments.

Well it runs and does not make any unusual noise's now *VBS* I am thinking about making another piston and raising the compression ratio up some W/O changing port timing. But I don't know what it is originally. Any comments on that???

I seem to recall reading somewhere that the comp ratio on the Mintor 22cc engine as being a 9:1 ratio, which would seem quite respectable for a sport engine.

Cyberwolf, sounds like that new piston for the Mintor 22cc engine you made is going to work out just fine. Good Work. About raising the compression ratio, it may just only place more stress on the engine. Not sure on that. See if you can go to the engine conversion forum & look for AV8TOR. He has ported many engines and seems to know a lot about porting & compression and the effects it has. I have really enjoyed trading ideas with him. We did a lot with gas/glow engines also. Keep up the good work, wish I had the range of tooling to do more with engines....its very interesting! Best Regards Capt,n from W Michigan

If that is 9-1 is sure is easy to turn by hand. But starts very easy with one flip after initial fire up.
I will tach it and check the timing, but it still feels weak on the comp side to me.
All the bowman rings I have used has broken in in a matter of minutes in fact most feel better than the stock ring W/O ever running.

Capt'n John a lot of the tooling for this project I hand made myself, Special angle cutter's and a.020 x.275 grooving tool was fun. The rest was either solid carbide or HSS ball mills and standard end mills.

I read somewhere the 9-1 compression ratio (in theory) is more like 6-1 actual, on a 2cycle engine. Not positive.

I have a Mintor 22 as well and it seemed to be losing compression. So I got a contact for Mintor through Chief aircraft where I bought it and Mintor finally sent me a new piston and ring. When I installed it I found that the hole in the piston for the pushrod pin was too large. So I put it back together anyway and turned it by hand and could hear a rattle. So I am not sure what to do now. It took almost 6 months to finally get Mintor to send me the part and it was the wrong one. Should I just put the old piston back in with the new ring?

You could trial fit the old piston to the new ring. Make sure the new ring is built the same as the old ring. On my engine those parts was changed a bit. My engine got a new rod, piston & ring. If you can, please take a clear photo of both & post it here. Thanks

tiger 650
I do know there was a ring design change, the location of the ring pin was changed to the side which before was down from the top. If your old piston has to much clearance like this one did, putting in a new ring is only a very short fix, because excessive piston slop will have the ring gone in no time. Chief says they don't have any parts now for the mintor line as well as top dog aviation,who sent all of there mintor line back to them. I searched like heck for some wrist pin keepers with no luck so I just made some new ones. I am still set up to make a piston if your interested let me know.

Cyberwolf, have you ever heard of this hardening process that may be used to harden crank pins?

My dad worked in a large engine building shop & he was in the heat treating department for several years. Anyway he would case harden knife blades we used for hunting...ect. So I did a search and found some ways to harden the metal surface of common steel. Click on link to read. Thanks Capt,n

http://tradetools.co.nz/products/2874710

Produces A Super Hard Surface On Plain & Low Carbon Steels

Easy-to-use compound case hardens plain and low carbon alloy steels. Carburizes surfaces quickly to uniform depth while retaining the toughness of the core. Also protects delicate, highly finished work, and helps eliminate the need for remachining. Simply apply the hardening compound to your metal parts, heat to the required temperature, then quench in oil or water for a professional grade, heat-treatment. Helps keep the edge sharp on expensive drill bits, milling and grinding tools, punches, firing pins, hammer davits, trigger pins, sears, and cocking pieces. Water soluble for easy clean-up. Complete

http://www.midwayusa.com/product/119...-compound-1-lb

http://tradetools.co.nz/products/2874710

Produces A Super Hard Surface On Plain & Low Carbon Steels

Easy-to-use compound case hardens plain and low carbon alloy steels. Carburizes surfaces quickly to uniform depth while retaining the toughness of the core. Also protects delicate, highly finished work, and helps eliminate the need for remachining. Simply apply the hardening compound to your metal parts, heat to the required temperature, then quench in oil or water for a professional grade, heat-treatment. Helps keep the edge sharp on expensive drill bits, milling and grinding tools, punches, firing pins, hammer davits, trigger pins, sears, and cocking pieces. Water soluble for easy clean-up. Complete

http://www.midwayusa.com/product/119...-compound-1-lb

Cyberwolf,
Thanks for the reply! I would be interested in a piston. I will have to give you the diameter of the wrist pin hole in the piston because that was the problem with the new piston that Mintor sent me. Would I then use the ring for the piston Mintor sent me for your new piston? Can I reuse the wrist pin keepers? Also, what is your price for the new piston? I apologize for all of the questions.
Thanks,
bob

That is a nice job on making that new piston. I think it is great you saved the engine so it can be used. It looks like it turned out really well too.

Cyberwolf,
The pin diameter is 7mm. Here are a couple of pics of the old piston and pushrod. http://www.rcuniverse.com/forum/atta...mentid=2041519http://www.rcuniverse.com/forum/atta...mentid=2041520
Please let me know if you need anything else.
Thanks,
bob

I would prefer to have the cylinder, old piston wrist pin bearing and wrist pin plus the new ring. the keepers you could keep. That way I can assure you a correct fit for all items. Send PM for price it is not allowed in public view, I have answered several but never started one so I don't know how *L*
It also appears to have some spacers to take up the side to side movement. Those I won't need as a new piston will fit the bearing with just a couple of thousands clearance.
Thanks earl I think the man will now have an engine that will run good plus last a while.

Capt'n John yes I have done what your talking about we used to heat treat and surface harden all sorts of metals. You can make a plain old carbon steels so hard for .030 depth that it tough to cut with carbide tooling ,but still has the flexibility of the softer metal.

Cyberwolf, I have 2 Supertiger 2300 engines. I was thinking of hardening the crank-pin on the crank so I could place a caged needle bearing in the big end of the rod to fit the crank-pin. I would bore out the rod to fit the O.D. of the needle bearing. Do you think that may work? Thanks Capt,n

Cyberwolf
Sent you a PM last night.
Tiger

Cap't it takes some specialized equipment to induction harden material. This is what I would do set the crank up and dial indicate the pin dead on both ways then carefully dill and bore the pin out of the crankshaft and open the hole to whatever size will give a dowel pin of the correct dia and length a good press fit of at least .002-.0025 interference. Press the dowel home and your there.

As far as boring out the rod I would source out a bearing that press's in the rod which they make, I would get in touch with Ken Lambert he converts Super tiger's all the time and would have the correct number and source of said bearing and dowel pin you will need.

[QUOTE=Cyberwolf;11903589] Send PM for price it is not allowed in public view, I have answered several but never started one so I don't know how *L*

Sending a PM is easy, just left click on the name of the poster in any particular post that you want to send a PM and a window will up and just click on the option you want to use and the rest is fairly straight forward.

Karol

Cyberwolf, PM sent.

*L* I sort of started a monster here. I have received several contacts about Mintor engine's. I figured that the 22 I did to start off was a factory slip up, but guys that doesn't seem to be the case at all. The 33 I got yesterday is a total mess as far as piston to cylinder fit. At the bottom of the skirt it has .006 clearance, the piston also has some taper in it and up at the ring there is .009 clearance I am not talking about the relief that's on all pistons either this is on the actual piston skirt. There are several more engine's headed my way we'll see if they all share this delema.