T head engine by Brian

[Steamchick]

Hi Brian,
I was half-expecting a c lever curved slot auto-disconnect - and a view of the miller showing the set-up for that weird shape... But you seem happy to start the engine and simply pull the drill-spud out to disconnect from the straight slots you have...?
John (Vietti): do you have a preferred supplier of the one-way or sprag clutch? (For us lesser mortals who have to buy more complicated bits!).
Ta,
K2

 

[Vietti]

K2,

Buy mine from BOCA bearings here in FL. Not much help since you are in the UK, but I think any large bearing supplier should have them.
Lately I've been adding electric start to my engines and the one way clutches are vital. Kids at the shows, of all ages seem to get a real kick out of pushing the button and starting an engine.

Good luck, John

 

[Brian Rupnow]

Vietti--can you send me a link to wherever you buy your electric starters please.----Brian

 

[Vietti]

Brian,

Have not bought any for a while but they all came from ebay. I think they are all surplus motors from battery drills, a little over 2" in dia. Just find ones whose size you like, have a voltage you favor and pay attention to the RPM. They seem very forgiving re voltage so voltage can be varied to suit rpm. Cheap too at around $10. Some come with a gear that's hard to remove. End up cutting 1/2 way through and splitting. If you have a junk drill, salvage the motor or buy a cheap used one at the junk store.

Most have a 1/8" shaft so I simply loctite a suitable, usually 1/4" shaft over it, looks shakey but so far no failures. For the remote start button I use a small solenoid made for Chinese scooters etc. The starter drive is 1/8 round belting, small chain or best yet are the small G2 toothed belts/pulleys. I tried gear drive but getting a large sprocket for the crank shaft is difficult and was really noisy. The starter is on a pivot so tension can be adjusted.

Its nice to start the engine without grabbing the drill etc. If you remember the video of the Silver bullet I posted, it has an electric start.

As I said, letting the spectators start the engine really delights them, I guess they feel more involved.

I'm a fan and happy to answer any questions I can.

John

 

[Vietti]

To find them on ebay type in 12 volt motors or as a sample, Mabuchi motor, $8, free shipping from US

 

[Charles Lamont]

do you have a preferred supplier of the one-way or sprag clutch?

Got mine, 8mm bore, from https://simplybearings.co.uk/shop/

 

[Brian Rupnow]

My second flywheel arrived today. As soon as it came, I grabbed it and ran down to my lathe and machined it. It's a beautiful thing!!!--Still needs a keyway and grub-screws, but maybe tomorrow-----

 

[Ghosty]

Brian, So you will have it running in an hour
Cheers
Andrew

 

[ShopShoe]

Brian,

I think it looks "right" with two flywheels. You've got the artistic eye design skills as well as the engineering skills.

I always look forward to new posts from you.

And, congratulations on the Do-All. I'm following that as well.

--ShopShoe

 

[Brian Rupnow]

This is the part where I never know what is going to happen next. The second flywheel has been keyseated, grub-screwed and installed. I have had some engines start right up at this point, amazing and delighting me. I have had engines that ran, but needed considerable tweaking before they ran well. And I have had engines that wouldn't run at all, because something was out of adjustment, the valves leaked, because I had machined something wrong, or perhaps the small engine Gods were just messing with me.---Wish me luck!!!---Brian

 

[CFLBob]

Well, of course I wish you luck, but I saw you checked the valves for leakage earlier in the week, so that one's probably good.

Plus, I've got to believe your experience at what to double or triple check has gone up enough that every engine goes a little faster than before.

 

[Brian Rupnow]

Okay---this one isn't going to take right off and surprise me. Fuel is getting ignited, cylinder is getting warm from firing. I'm not feeling a lot of compression here. The old "oil down the sparkplug hole" trick isn't bringing the compression up any, so this infers that the rings are doing their sealing alright. I will check again to make sure that there is daylight between the valve stem and the lifter when the lifter isn't up on the cam. (this will hold the valve open and no compression will be developed.) Since it does seem to be firing more or less consistently when driven by my electric drill, I will now put an electric motor to driving it, and see if the valves will seal up from the pressure created by the engines firing. if it wasn't firing at all, I wouldn't do this.

 

[Brian Rupnow]

It seems that I have a leaking exhaust valve. Rather than screw around with everything bolted to the engine, I have made a "dummy cylinder" to bolt the cylinder head to. It is an exact copy of the cylinder, but without the center hole for the piston. First thing to check is whether the valve can be rotated into a position that doesn't leak. That technically shouldn't happen, but it sometimes does. Without changing anything on this set up, I can seal the leaking exhaust with my thumb and thus check the intake valve for leaking. I know that I used this same piece of equipment with the "blow yer guts out" test to see if the valves were leaking or not. They didn't seem to be then, but everything gets handled a great deal between that test and when the engine is finished. Today I will test things at 40 psi.

 

[Brian Rupnow]

Compression has improved. Engine is now firing regularly along with power drill as I attempt to get it to take off and run on it's own. Cylinder is getting hot from firing. I am now going to take my degree wheel and check the ignition timing. The common knowledge out there is that four cycle engines should fire about 20 degrees before top dead center. Lots of puffs and snorts from the engine but haven't found the sweet spot yet.

 

[Brian Rupnow]

No joy today. Very, very close, but no engine running on it's own. I'm having some kind of compression issue, and I think it is in the valves. Tomorrow I will reset the valve timing with my degree wheel, but my gut is saying it's a valve sealing issue.

 

[oldengineguy]

Brian; A sprague clutch or one way bearing is cheap $6-8 CDN. available from Canadian Bearings (branch in Barrie).Much easier on drill ,wrist and engine. When its hard to start it just overruns the drill rather than having to stop and reinsert the pin in the slot. Colin

 

[johwen]

No joy today. Very, very close, but no engine running on it's own. I'm having some kind of compression issue, and I think it is in the valves. Tomorrow I will reset the valve timing with my degree wheel, but my gut is saying it's a valve sealing issue.

How about your Valve spring, does it have enough tension to seat the valve each time? cheers. John ( love your build Brian)

 

[Brian Rupnow]

Johwen--The valve springs don't have to exert a lot of force to close the valve. Once the valve gets near the seat, the expanding fuel charge will force the valve into it's seat and seal ---IF--the valve and seat are machined correctly. Hi revving engines need very strong valve springs, in order to get the valve closed in the very limited time that is available to move the valve from open to closed.--On low revving engines like this one, springs don't have to respond so quickly.

 

[petertha]

I'm interested in your choice of carb (the Traxxas 4033 for RC car). Coincidentally I was going through a list of RC (aircraft) methanol fuel carbs for my radial engine with coincidentally similar barrel orifice (6mm). I didn't think to look at RC car/buggy as aircraft carbs seem to be slimmer & slimmer pickens.

Are you running gasoline? Is it mostly about the orifice size? (you mentioned possibly other carbs). Does the low & high speed needle valve adjustment provide you the adjustability to require? Just curious.

 

[Jasonb]

My engines tend to run a 5 to 10deg BTDC, your 20deg sounds a bit early to me particularly for these slow running types.

that way you are more likely to get all the explosive force pushing the piston down, too early and that force is pushing down on the piston while it's still coming up and on it's own the engine does not have the power to overcome that. Also tends to cause more backfires but you won't be seeing that pushing it round with an electric drill, I see it more as mine get started by flicking the flywheel or a short pull cord.

EDIT I just looked at what hamilton Upshur suggests for his Tee Head and it says "a little Before TDC" which I would take as less than 20deg