Thread: good blade but Bi-metal or tungsten tip

Sorry for the delay in posting some photos, lots going on!

1st photo from the left (PFTL), front on view showing the car rims - they are about 400mm across, also the blade/guide bearings.

2nd and 3rd P.F.T.L. showing car rims l got from the tyre yard, the larger rim is ok 500mm across behind the rim edge.

4th and 5th PFTL are showing the tension set up.

6th PFTL is the depth of the rim 25mm ie where the blade sits, so if the blade is wider than 25mm then the teeth DO NOT hit the rim, as the blade can not go back any further. ie 31mm blade

7th PFTL shows the bearing housing etc.

8th and last photo shows the 8" pulley belt, the belt is tensioned via a partly obscured wheel at the top of the photo this wheel is lowered and locked into place via a spring loaded button/knobby thing.

Now looking at the newer rims, l thought there is a lot of work there to get them right, so me being a lazy so&so, thought how would l go making larger timber wheels from marine ply or similar say 600mm across x 30mm wide and attaching them to the existing rims, yes the guard would have to be modified but thats no hassle, l can get tyres made to suit from the US, or use bike inner tubes?

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Any thoughts if my ideas would work, taking into consideration that the blade suppliers wouldn't sell me blades because of the smaller rims and no tyres.

Do l need to replace the 8" pulley to something larger or smaller? to get the optimum cutting speed?

Hope some of that makes some sense, couldn't fully uncover the saw, limited time.

Stevo

Originally Posted by Not enough!!

Now looking at the newer rims, l thought there is a lot of work there to get them right, so me being a lazy so&so, thought how would l go making larger timber wheels from marine ply or similar say 600mm across x 30mm wide and attaching them to the existing rims, yes the guard would have to be modified but thats no hassle, l can get tyres made to suit from the US, or use bike inner tubes?

I think bike inner tubes will be too soft. The polyurethane tyres on the 19" BS in my shed are quite hard and the BSM in the tree loppers yard (670 mm wheel diameter) uses very hard C section fan belts.

Any thoughts if my ideas would work, taking into consideration that the blade suppliers wouldn't sell me blades because of the smaller rims and no tyres.
Do l need to replace the 8" pulley to something larger or smaller? to get the optimum cutting speed?

If you don't know the cutting speed at the moment we can't really advise you which way to go?
The info needed to determine blade speed is motor RPM in the cut, and the the size of the drive and wheel pulley.
Have you actually had it cutting?

One thing I notice with the first photo is the guide on the right seems to be level with the RHS wheel while the guide on the left is higher than the LHS wheel.
I wonder why it was made like that - normally the guides are ~1/8 to a 1/4" below the wheels.

I don't like knocking home made gear but that tension system looks a "tad awkward" compared to the hydraulic ram on the BSM on the mill I'm using.

Just a couple of thoughts....rather than attach to the existing rim, Is it possible to take the al rim off and then make up a wheel that you then fix onto the blue hub?
Also, for a tyre to suit the existing rim, Have you thought about a car tyre? you might have to take it into a tyre place and let them look at it, Do you know what those existing rims came off? What about a motorbike tyre? something with not too much tread and with a bit of a curve to it

As Bob says we would need to know an approx engine rpm, engine drive and driven pulley sizes, and blade wheel size, current ~400mm and propsed ~500 to 600mm to work out a blade speed.



Pete

Thank you for both answering my questions.

If you don't know the cutting speed at the moment we can't really advise you which way to go?
The info needed to determine blade speed is motor RPM in the cut, and the the size of the drive and wheel pulley.
Have you actually had it cutting

Bob, the motor is 6.5hp ( max RPM 3500 ) motor pulley is 50mm OD, as l mentioned before shaft pulley is 200mm, l know it needs a bigger motor, but l just want to get it running properly first, l have a couple of logs to get of quickly, as l don't like having them clogging up my mates yard.

Blade guides needed updating as the guy used spacers rather than thread connectors, and the bolts bent, and l didn't line the new ones up properly, they have vertical adjustment so l'll fix that tomorrow - thanks.

It has cut timber Cypress and pine 600mm wide, blackwood 500mm x 25mm thick using a M42 Bi-metal 3/4 tooth 6 degree 4420mm blade, but these blades bog down too quickly so that is why l wanted to go to less teeth, bigger wheel so as too relieve the stress on the blade, less teeth thicker blade, bigger wheels.

Just a couple of thoughts....rather than attach to the existing rim, Is it possible to take the al rim off and then make up a wheel that you then fix onto the blue hub?
Also, for a tyre to suit the existing rim, Have you thought about a car tyre? you might have to take it into a tyre place and let them look at it, Do you know what those existing rims came off? What about a motorbike tyre? something with not too much tread and with a bit of a curve to it

Pete, l am thinking of making a couple of ply wheels so 25mm or 30mm thick, l am not keen on car tyres, l saw a guy on you-tube with car tyres and it looked too dangerous!


Steve

Originally Posted by Not enough!!

Thank you for both answering my questions.

If you don't know the cutting speed at the moment we can't really advise you which way to go?
The info needed to determine blade speed is motor RPM in the cut, and the the size of the drive and wheel pulley.
Have you actually had it cutting

Bob, the motor is 6.5hp ( max RPM 3500 ) motor pulley is 50mm OD, as l mentioned before shaft pulley is 200mm, l know it needs a bigger motor, but l just want to get it running properly first, l have a couple of logs to get of quickly, as l don't like having them clogging up my mates yard. e

Thanks for the info.
With a motor to wheel pulley ratio of 50:200 thats a 4:1 reduction in RPM or 3500/4 = 875 RPM

With 13" wheels that's 3000 FPM, with 18" wheels thats 2900 FPM and with 19" it 4350 RPM - the ideal speed is supposed to be 5500 FPM

However it's unlikely that such a small motor will hold its max RPM in the cut and would be even less likely to hold max RPM if the 200 mm pulley was replaced with something bigger to try and improve the band speed.
To reach 5500 FPM you will need 24" wheels BUT I doubt the 6.5HP motor will have the torque to drive the 19" wheels in a cut let alone 24" wheels.

Rather than fork out for an expensive blade maybe you should just get a cheapie to see if it will even run with the projected changes in wheel sizes.

By way of comparison, the BSM I'm running has a 27HP motor with 26.5" diameter wheels that turn at 770 rpm in the cut, which works out at 5100 fpm

Bob, thanks again for that, got some research to do on the safest and easiest way to increase the wheel size, l asked the guy l brought it from to check the wheel size on the steel cutting b/saw the old bi-metal blades come off.

Steve