Briggs powered compresser

I've been building up a compressor . It's now powered with a 3hp Briggs engine . Small problem with starting , not quite enough torque with the vee belt tight.. Retightened whilst running ,it drives the pump fine ,so i'm using the belt as a disengaged clutch to start it .. Which brings me to the jockey wheel i'm going to fit... Does it really matter if its trailing or leading ? I wonder if there would be a little servo effect if leading? I know it should go on the slack side of the belt, but what do you reckon ? Engine is on the right ..

Like this \/ \/

Or this way \/ \/ or doesn't it make any difference ?

Edited By Hacksaw on 16/06/2017 19:18:10

Edited By Hacksaw on 16/06/2017 19:21:11

I would have it set up as per the top picture .

I feel your problem has more to do with the drive pulley ratio , i would be looking at something like 4:1 or 5:1  and some sort of decompressor valve on the pump so you are not trying to start the engine under load 

Ian 

Edited By XD 351 on 17/06/2017 00:30:14

As XD 351.

Many buzzbox alloy compressors are driven at near 3000rpm. Better to buy an old cast iron two stage pump that will do the job at about 500rpm. Many of these inefficient pumps need 2 or 3 kW, so a small briggs may be ''hissing into the wind' to drive it properly. Even better would be to gef a decent Honda engine!

Briggs engines were rated as a flash horse power, not continuous. That is why the Honda engines of the same nominal power (but DIN rated) were deemed such better engines.

I once had a generator, rated at 1.5kW, driven by a briggs. It would stall out while trying to start a freezer, unless it was given extra revs to overcome the motor starting load. Freezer was rated at 160W, so would have needed about a kW at start up.

Hacksaw,

go with the first photo.....

done something similar but with a Lister Diesel.......on the outlet pipe from the comp I used a lever type ball valve (couple of quid from the likes of Screwfix) to dump air for start up........do what "not dun it yeti' sorry, says, go for the old style cast iron compressor, mine is over 50 years old and nice and quiet.....elec driven tho......

as for the Honda engine, that's if u go that route....

2 things, if it doesn't say "made in Japan" don't buy it...it'll be a Europeam made peice of crap, loads'a problems with carb's and pistons.....always thowing them away here in France.....and for a new copy replacement Honda, u can get small 1 for around a €100'ish, this is a Cjinese copy engine complete that are excellent value and do last...I think the GX160 larger eng is about 150-160......use them quite often as replacements for mowers and w/pumps.........in fact my power washer has 1 (machine bought new) and that works hard and is now 5 years old......

just saying Clogs

Yes , I'll fit an unloader valve . It is a cast iron barrel pump.. I don't know its cfm , but when it had an electric motor on it , it was just about enough to spray paint continuously with a devilbiss gun . I nicked the motor for something else ...I,being a hoarder, thought it about time i did something with it , piles of mower junk turned into a portable compressor !

I've got another compressor , started off as a plastic piston ring rubbish direct drive pump but i changed the whole lot to a iron ring pump with a sump , I bought from the classified on here .

Not relevant here as you have already made a jockey wheel but car auxiliary belt drive tensioners are an excellent source of jockey wheel assemblies. Many being bolt on units complete with spring on a sturdy mounting plate or casting. Certainly something for the "come in handy" box when you change a belt on a higher mileage vehicle or even, quelle horror, bought new. Pattern parts more than good enough for this job can be found for around £20 - £30.

Sub £50 for a nicely engineered widget is where I start seriously considering the buy rather than make option if I don't have owt suitable with very simple rework on t'shelf.

Clive.

Nah ,i didn't make it ... it's from a Suffolk Colt mower !! I only drilled a 9.5mm hole and whacked the pivot pin out of the casting and into a bit of steel...

Who said the pulley ratio could be better? He was right ! Stalled right out when i loaded the belt. Bored a new smaller pulley and cut a keyway, Starts and runs gooder now , but this pulley is light alloy with no flywheel effect ,so when i use it, i'm going to start it with the belt slack , leaving the tensioner off ,and run it until it's warmed up unloaded, set the throttle and then tension the belt.

That fan pulley on the compreessor will not have such a high speed rating, I would think. Beware.