Weed Wacker Revisited.

Great running dialogue with lots of good information, Deacon. tnx!
I'll drill out the mounting holes now, and get that over with.

CB2... Tnx I shall fab an air scoop for cooling. No plans for idling in traffic, but as they say, plans rarely survive implementation ! LoL
I had made plans for a scissor lift to raise the engine roller up off the tire when stopped. I suppose I can shut down and re-start if stopped for more than a common traffic light. There ain't many in my two-horse two, anyway.


....More pics, Deacon!
I like pics !


Best
rc

Cool Deek! Is that a wheel hub it pivots on? You should have no problem starting like you mention. However you will have little to no cooling with out the fan shroud. Gut the recoil and see if you can fit the shroud, will have to open the hole size where the recoil was to accomadate the roller. Need to get some air through the cylinder

Deacon,

Wow! Ur welding s***s !

...Sry, the devil made me say it! LoL

Great test bed. That's what counts.
I am learning and considering more options just from viewing your pics!

I have kinda planned for some sort of abbreviated shroud, hammered from lite sheet stock, to direct some air from the central crank area through the centrifugal fan, OR, a scoop as CB2 suggested if I'm NOT going to idle the engine. I did mill down the fan blades on my flywheel, so the roller was not hanging out so far from the sole bearing support in the engine. My machined roller also has an outboard bearing which I'll need to support on the opposite side of the fork supporting the engine.

On a thread elsewhere, a member has requested engineering support regarding a bicycle frame... I think some could be used here, in relation to the swing angle of the mount in relation to the contact point of the roller upon the tire.
Where you employ a spring to force the drive assembly, it should be possible, with the correct geometry, for the roller to 'dig' into the tire when power is applied, and the function of lift on the assembly should actually limit the amount of friction applied to the drive mechanism. A certain amount of spring tension will always be required, to mediate irregularities, but that, and the weight of the power unit should not be the controlling factor for the drive.
IMO LoL! Just some thoughts that have come to mind, viewing your pics...
FWIW

Good work Deacon! I enjoy your thread a lot.
Best
rc

I actually use the clutch cable to set the drive tension, I tension it until I get slip under heavy throttle then start backing off until it gets just to the point where it doesnt slip. I actually do this while riding. Of course it only works like this with a lift clutch.

Thanks for the reports on the experiments, Deacon.
I read every single one!
Your results have led me to reconsider a lot of things I might have done that would not have worked out quite so well.

Ha! I was just joshing you over the welding... if it works for the prototypes, run it! I still tack mild steel using coat hanger wire and weld copper with stripped electrical wire scraps. I've got fancy store-bought rod, but save it for projects that are critical to me. I'm a cheapskate!

100mph tape is a good product because the adhesive is flexible and will not randomly give out due to vibration. But it will give up! OK for experimenting, but if left on for too long, however long that is, watch out for things sailing through the spokes!
IMO Nashua brand duct tape is the best, and the 'lathers' use a red colored duct tape in construction for putting up their plastic that will handle wet surfaces better, which could be something you might run into when on a bicycle...

Best
rc

Hey Deacon,

I agree that a bump start is probably best for these little rack mount friction drives. A recoil starter is a handy convenience for a homeowner with a less mobile application.

Since we're dealing with a machine that requires a pedal start even when running, might as well leash some of that momentum to start the motor assist !

You'll probably find the engine starts better with the larger roller because the friction is superior because of the larger bearing surface, and the ratio will spin it faster at start. Of course the smaller pinion will perform better all around because it is more suited to the torque and rpm range of the engine, suffering only because of friction bearing surface at the tire.

When I looked at your pics the other day I thought you might benefit well from an $8 wallyworld chengshin cruiser tire instead of your MTB tire which is nearly gone, anyway. A thorn guard might be a good idea, too, to help with dealing with the additional heat generated by the friction drive. Perhaps others could present some input on that effect.

...a number of years back, a kid on a mini-bike pulled up to where I was working, to talk with a friend of his that was part of my work crew. It was stripped down to the basics... I expect a lot of parts had fallen off or gotten lost. Lol

After his short conversation, he put his foot on the flywheel and spun it forward with his tennis shoe, the briggs started, and he took off.
It's all good !

I didn't mean to throw you under the bus over the welding, Deacon. If it gets the job done, that counts. ...Recently I've been participating over at the Longevity welding forum and the fellows are showing off their fabulous welds on any number of projects... my own aren't near up to their standards. Some do textbook quality welding in their posts. They are beautiful. One small variation in a bead may generate a dozen responses, in great detail, on techniques to resolve the situation. It's educational, and fun.
My own tig welds would never meet their standards! LoL

Best
rc

...know what you mean, Deacon... years back I wanted to teach our boys to gas weld, mentioned it to a friend, and he pointed out the fire potential in our area... summer, this place is a tinderbox... so I thought it wise to pass until the boys were older and more responsible.

..the biggest fires around here were all started by the forestry department when a controlled burn got away from them... 2nd in line has been someone doing weed abatement makes a spark and sets something off. 3rd is lightning strikes.

When I get my MABs going, I'll need to install a .022 ss arrestor screen just to make sure the are no problems on my account. That would be a bad thing.

Best
rc