quarter-turn v belt drives
I want to make a quarter-turn (right angle) v belt drive. Looking at design and reference materials I can find online, it appears to be nothing real special so long as the distance between the pulleys is appropriate (about 6x the larger sheave diameter.)
I'm wondering if anyone who's familiar with quarter-turn drives has any advice regarding pitfalls, etc.
I remember a couple of fair sized hand pushed rotary lawn mowers where I worked years ago. These had a horizontal shaft Villiers engine driving a vertical shaft for the cutter plate. The engine pulley was standard B section, but the cutter shaft pulley had a deeper and wider groove than standard. Thinking back, I think the angle of the belt groove was probably standard - not sure of this though. Shaft centers would have been around two feet or a bit more. From memory the larger pulley would have been about 8", so this was a long way from your suggested shaft spacing of 6x pulley diameter, which was probably the reason for the wider groove. I don't recall any special problems with excessive belt wear or mechanical failures even with the short center drive on these machines, which were in use for 30-40 hours per week.
The GM Corvair used a system like that to drive the cooling fan from the engine crankshaft.
Are you familiar with the right angle belt cooling fan drives on Corvair engines? They were mass produced and you always wanted to carry a spare belt. There was real engineering effort expended on it but it beat the snot out of belts. There are lots of photos of the Corvair arrangement available with google images. The turning sheaves need to be positioned and angled correctly.
Don't expect long life from the belt if operated at high speed. The smallest section belt adequate for the job is the best choice, hysteresis heating kills V-belts. Low speed, no sweat.
Did 1960-70's upright hoover vacuum cleaners have a 90 deg belt to drive the sweeper mechanism from the main motor? IMS the belt was a circular 'O' ring kind of section which ran in a shallow curved groove with a lot of side relief on the drive and a full curved groove with a little side relief on the sweeper.
I can't remember the size difference between the driver and driven, the tension was given by the elasticity of the belt.
Maybe this will help in some way.
Cub Cadet was the most common mfg to use r/a belt drives.
They used deep groove pulleys, one idler fixed the other was spring loaded(on the slack side).
Belt runs deep in the pulleys, sort of like a "B" groove with a "A" belt.
It's been a while but I think the belt had a different side pitch than normal, steeper angle.
Engine ran about 3300 with the engine pulley approx 4.5 pitch dia.
They used a reinforced belt, did quite well.
Cheap belt, not so good.
A number of vertical head conversions for small horizontal mills, notably the "Marvin", used a quarter turn belt. (Actually, the belt turns a quarter turn on it's axis 4 times in one trip around)
being smaller mills, they naturally had nothing remotely close to a 24" shaft spacing, more like 8" or so going up to the idler, less from idler to spindle pulley.
If one uses the smallest belt size, in a notched belt, does that help?
I would suppose the real guiding dimensions should be related to the belt itself, in terms of distance in belt thicknesses, or the like... A belt with a 3/16" cross-section, like the silly "thread" used on some old Sears drill presses, would presumably not be affected as much by a quarter turn in 4" as a belt of a half inch cross-section.
iirc the browning catalog offers engineering for setting up quarter turn
i have built several and have had excellent luck with them, the key is using quality components, rigid mounting and most of all the best belts you can buy. i prefer the notched belts like the AX series.
personally i think the biggest problem with the corvair application was folks using cheesy cheap ass belts on worn grooves, and other alignment issues. the higher engine speeds would bring out the weak link quickly.
if i were to build another QT drive i might look into the use of an AA section belt, running in B grooves.
Picking up on points made by others - we used to make some light-duty quarter turn drives using off-the-shelf Fenner 'Bi-loc' pullies which are grooved to suit both A and B section belts. So you can use an A-section belt while benefitting from the extended vee-sides as a lead-in.
We machined and filed a radius onto both sides of the vee-groove, so the belt didn't wear on a sharp corner as it ran off, or onto, the pulley.
We used a round-section polyurethane cord (about 8mm or 10mm diameter, mustn't bottom on the pulley though) as a belt, or sometimes an 'A' section Fenner Power-twist, or NU-T-Link belt (these are the Brammer (?) type link belts). It is important that the belts don't touch where they cross, especially the polycord which will quickly overheat. The only reason we used poly cord and link-belts was because we had fixed centres, otherwise I would avoid them like the plague.
BTW, after playing with these things for a few years, I hate them all! Especially poly cord drives. Yes they worked...but they were not trouble-free. We always had spare belts on the shaft. Our centres were pretty tight, maybe 250mm using 80-100mm diameter pullies.
Having said that, we had a 'Hayter' mower (still have it actually) which was exactly as Franco described, and never had any trouble with the standard (B?) v-belt and deep groove pulleys', I think the centre distance was quite large (at least two feet) and the pullies probably 4" and 5". I think the decent centre distance must help, plus a ordinary, strong, un-notched vee-belt.
i forgot to mention a couple of other points worth a mention
center distances are important, as are placement of the quarter turn pulleys or driven components, if the to main pulleys are the same size then the pulleys at the "turn" must be perpendicular to the drive/driven pulleys (90 degree's), if on the other hand the drive/driven pulleys are anything other than the same size the quarter turn pulleys will need to be at some other angle other than 90 degree's, also
once the design is properly engineered, the belt length designed around will be the only belt that will maintain the integrity of the design, "if" the tensioner is one of the quarter turn pulleys and not the drive or driven pulley.
this is likely what caused lots of problems with the covair system, folks would use a belt that was a bit longer because that was what was available, thinking they could simply adjust the generator/alternator to take up the slack and in doing so change the geometry of the design.
done right a quarter turn system works very well in my experience up to at least 3600rpm powering a 6" driven and 6" drive pulley.
all adjustment in the design was accomplished by moving the driven pulley which maintained the geometry of the design.
Comments encouraging. I will give it a crack. Btw, the application is driving a belt sander.
I used to maintain a t bar ski lift that had 4 v belts with a 1/4 turn. They ran for years I don't ever remember replacing them even when we replaced the flathead 6 with an electric motor.
How about a round belt?
I think the hoover used an o-ring drive. Small pulley machined outboard onto the vertical-axis suction impeller, going around the horizontal beater-bar.
My Dad's company made heavy duty lawnmowers, and had the vertical/horizontal arrangement, with idler pulleys between the driving and driven shaft, as mentioned by Franco. Also, someone mentioned the marvin mill attachment. Here's a pic, from lathes (look at the left pic).
It is totally do-able. Only caveat I can think of other than getting the angles and alignment correct is that you should provide for easy access to belt replacement. The belts will just not last as long as on setups with pulleys in the same plane.
Not sure whether you're talking about a crossed shaft drive, connecting two shafts parallel in one plane and perpendicular in the other, with only a driving pulley and a driven pulley, (as Peter S was describing)
or a right-angle turn drive with two idler in addition to driver and driven, as shown in the first of Bosleyjr's photos.
The former. In the US I believe "quarter turn belt drive" is a somewhat standard term for this, as I found that term used for this in two power transmission catalogs (Gates and Martin Sprocket) and also in a couple online machine design textbooks.
Originally Posted by Troup
The latter drive, I found in a book referred to as a "mule pulley drive".
Quarter Turn Drive:
Ir my memory is still correct, one of the major requirements is that the centerlines of the belt groves on the tension side must be in line and the twist must be on the tension side also. Any misalignment must be on the slack side. Otherwise the belt will jump and be very short lived. Both Dodge and, as someone mentioned Browning, used to have good design info in their catalogs. Deep groves on the pulleys are also good as are fabric covered belts - similar to those used on lawn mowers
My 18 HP Sears GT has a horizontal shaft engine, deck drive belt on the front shaft, maybe 5 inch sheave, maybe 10 inches down to the idlers that allow the belt to make a 90 deg bent to vertical sheave on the deck.
Aft shaft, again about 5 inch sheave, about 10 inches down idler and tensioner (and declutch), AND a 1/4 twist in the belt to the vertically oriented input sheave on the tranny.
I have 2 of those tractor, and in 22 years I have changed the deck drive belt twice, and the main drive belt never. Only a month or 2 ago did I even have to take up any slack in the main drive adjuster, and that less than half an inch.
I think you can safely make your 90 deg bend.
On the deck drive, from the "bend" sheaves to the deck sheave is approx 2 feet. On the main drive, probably 20 or so inches.
I will tell you that the braid covered belts for outdoor equipment lasts a lot longer than the Gates Power whatever, rated?, the cut belts. That I found out with my kid's Bolens.
I have four home built polishing spindles that use a quarter turn belt drive, the pulleys are 3 inch on the motors and 4 inch adjustable on the spindles, the spindles and shafts are about 16 inches apart. They have 2hp motors automotive belts 1/2 wide, they are about 5 years old and run a couple of hours each most days. I haven't replaced any belts or pulleys yet. Hope this helps.