Homemade Tiltrotator - How hard can it be ??

[jd6820]

Having tried a few different orientations, I’ve now put together a rough model of an externally mounted drive.

The idea is to run a 50cc OMM motor (with a dual cross-line relief valve) as I’d need to limit pressure down from the machine’s ~180 bar. From what I’ve seen, this is the same displacement motor used on an Engcon EC02 and a Rototill RC1.

Drive concept​

• Motor mounted externally (to reduce rear overhang / improve clearance)
• Drive transmitted using an HTD timing belt
• Taper-Lock pulleys on both shafts

I now need to work out the best way to tension the belt:

• Sliding motor mount (adjust motor position for tension), or
• A separate tensioner/idler pulley

let me know what you all think ???

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Keep it simple on the belt front, slots for motor to allow adjustment. A belt that short isn't going to require much travel for tension. Looking good.

 

[V8Druid]

Keep it simple on the belt front, slots for motor to allow adjustment. A belt that short isn't going to require much travel for tension. Looking good.

only issue with a sliding motor mount is keeping the tish out

 

[Will_c]

Made some progress on the external motor mount .
Utilises two 22teeth 8M HTD pulleys and a 360mm belt 30mm wide.
My thoughts are a steel backplate then an aluminium case to cover the pulleys.
The motor is on slots to allow for it to be tensioned

 

[Will_c]

Tiltrotator length comparison.

 

[Monkeybusiness]

Made some progress on the external motor mount .
Utilises two 22teeth 8M HTD pulleys and a 360mm belt 30mm wide.
My thoughts are a steel backplate then an aluminium case to cover the pulleys.
The motor is on slots to allow for it to be tensioned
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@V8Druid ’s suggestion of gears seems a great idea to me (though what you are proposing here is very smart). It’ll want the slots sealing somehow though.

 

[6feetdown]

Yeah 1 to 1 gearing sounds better to be than a belt

 

[Quattromike]

Has anyone here had experience welding a trunnion mount onto a hydraulic cylinder?
I’m planning on sourcing the cylinder itself from Steerforth in kit form and then welding it together. One issue I’ve run into is that the inlet/outlet port on the cylinder barrel is already welded in place which complicates trunnion placement.

To mount the trunnion, I’m currently considering two options:

1. Machine a U-shaped relief in the trunnion to provide clearance for the hydraulic port
2. Manufacture the trunnion in two halves, position it around the cylinder, and then weld the halves together once in place

I’m unsure whether either of these approaches is best practice, or if there’s a better way of doing it without risking distortion
Any advice, alternative ideas, or examples of this would be very welcome.

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I'd be cautious about welding the trunion on to a pre machined cylinder. the steerforth head glands have an oring below the thread that's oversize to the cylinder bore, it makes it difficult to hone. If the cylinder distorts with welding it'll either be forever slackening or leak.
You may be better getting a honed bore tube from HSL or similar and doing all the welding first then machine the head gland threads. That be best way to ensure a good result.

 

[jd6820]

only issue with a sliding motor mount is keeping the tish out

I don't think it'll need to move very far if the belt is a stretch fit to start off with. It's a very short tooth belt that I'd bet doesn't stretch very far and if the holes were slotted within the motor flange size then it would remain covered. Else a plate fabricated to cover the mounting points. Like you say gears is the best option but maybe @Will_c has a timescale/budget that doesn't stretch to gears? It'd mean designing a gearcase with grease or oil etc...

 

[Will_c]

I don't think it'll need to move very far if the belt is a stretch fit to start off with. It's a very short tooth belt that I'd bet doesn't stretch very far and if the holes were slotted within the motor flange size then it would remain covered. Else a plate fabricated to cover the mounting points. Like you say gears is the best option but maybe @Will_c has a timescale/budget that doesn't stretch to gears? It'd mean designing a gearcase with grease or oil etc...

As you said @jd6820 the slots are covered via the motor flange. The reason for using a belt is ease of assembly and will be less parts I need to manufacture/machine . I can purchase the timing belts and pulleys fairly quickly from different suppliers.
I have thought of the use of gears but it would require 3 gears along with another pin for the idler gear so additional bearings in the assembly.
The cover is recessed 2mm into the back plate to stop debris from entering.

 

[Quattromike]

two 1:1 gears would be easiest IMHDO ... a belt is always going to be troublesome, keeping it tight

Don't think a timing belt is difficult to keep tight enough to drive but I'd be concerned about it coping with the torque from the motor. Would a chain drive be an option?

 

[V8Druid]

As you said @jd6820 the slots are covered via the motor flange. The reason for using a belt is ease of assembly and will be less parts I need to manufacture/machine . I can purchase the timing belts and pulleys fairly quickly from different suppliers.
I have thought of the use of gears but it would require 3 gears along with another pin for the idler gear so additional bearings in the assembly.
The cover is recessed 2mm into the back plate to stop debris from entering.

what do you need an idler for ???

 

[doobin]

Don't think a timing belt is difficult to keep tight enough to drive but I'd be concerned about it coping with the torque from the motor. Would a chain drive be an option?

Never looked inside a tilty worm but presume they have ball screws or similar to reduce backlash? Chain drive would introduce an awful lot of backlash.

 

[V8Druid]

Never looked inside a tilty worm but presume they have ball screws or similar to reduce backlash? Chain drive would introduce an awful lot of backlash.

nope ... just a plain old worm/screw drive .. big bronze planetary/crown and a steel screw -metal to metal

 

[Quattromike]

Belt would probably work fine but I'd possibly be leaning towards a heavier belt.

 

[Will_c]

Belt would probably work fine but I'd possibly be leaning towards a heavier belt.

Running some calculation further calculations of the belt size a 30mm 8M HTD is sufficient if both pulleys are 24 teeth. ( of course this is dependent on the grade of belt )
Maximum motor torque is 60 Nm which then goes into the word drive at a 47:1 reduction

 

[Will_c]

I'd be cautious about welding the trunion on to a pre machined cylinder. the steerforth head glands have an oring below the thread that's oversize to the cylinder bore, it makes it difficult to hone. If the cylinder distorts with welding it'll either be forever slackening or leak.
You may be better getting a honed bore tube from HSL or similar and doing all the welding first then machine the head gland threads. That be best way to ensure a good result.

Not sure I have the facilities at uni to be able to machine the threads into the cylinder ?
@CPS You said you normally use a sacrificial head gland when welding trunnions on ? - Where do you source your cylinders from-is it the same with the oring below the threads ?

 

[V8Druid]

the other answer to this would be to machine up a split trunnion cover to clamp to the rod end of the cylinder and around the port

 

[Will_c]

the other answer to this would be to machine up a split trunnion cover to clamp to the rod end of the cylinder and around the port

I am contemplating this approach would stop any weld distortion . whether there would be enough clamping force to hold the cylinder in place its another question ?

 

[V8Druid]

Running some calculation further calculations of the belt size a 30mm 8M HTD is sufficient if both pulleys are 24 teeth. ( of course this is dependent on the grade of belt )
Maximum motor torque is 60 Nm which then goes into the word drive at a 47:1 reduction

have you factored into your calc.s the possibility/probability of the drive being driven against an 'immovable' object ??? ... this is not 'just' a conventional 'drive', as we would 'normally know it'

 

[V8Druid]

I am contemplating this approach would stop any weld distortion . whether there would be enough clamping force to hold the cylinder in place its another question ?

locked around the port would considerably help the clamping action and machined with a 2-3 thou. interference fit, ought to do the job